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Offline aouate3Topic starter

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16 year old needs help building a robot
« on: July 30, 2011, 06:11:06 PM »
Well as the subject clearly states, i am 16, and im building a robot, been wanting to do it for a while, but i didnt have the funds.
I repair computers, electronics, and mechanical devices, and have been doing so for about 10 years (yes, since i was 6)

The robot i am constructing will consist of 4 cordless drill motors with there gear boxes, mounted on a sturdy chassis, with 6 or 8 inch wheels.

The motors will not have speed control (yet, maybe in a future upgrade) but they will have forward and reverse control

the motors on the right and left side will have independent control (as in, the right sides control will be seperate from the left side)and controlled by 2 H-Bridges consisting of relays (because i have a box full of new ones)

my shematic is attached (i put this together in 5 minutes, but it came out ok)

The "brains" of the robot are already built, Consisting of a Arduino UNO microcontroller, and a Linksys WRT54GS router flashed with OpenWRT
the communications from computer to microcontroller are done using the router, got the source code and info from http://www.jbprojects.net/projects/wifirobot/

The voltages i will be needing are 9 volts  (or 5 volts 500ma, but the M.C.'s regulator can handle 9 volts easily), 5 volts 1 amp for the relays, and 12 volts for the motors, but i dont know the amperage, because i dont have the motors yet.

I need to know a few things

How should i supply power, what type of battery, battery chemistry, battery voltage, battery type, battery amperage, etc?

what can i do to protect the circuits (i think i have what needs to be protected protected, but i dont know for sure)?

Should i have a seperate battery for the "Brains" of the robot ( the Arduino and Linksys wrt54gs)?

Should i use different motors instead of drill motors? i was planning on using 4 cordless drill motors with the gear box, and just hacking the gear box so it supplys constant torque.

I have the H-bridges already built, but i need to get 3 more transistors from the "rat shack" im using MPS2222A transistors, for the diodes im using 1n4004, and the resistors on the transistors base pins are 1k ohm 1/2 wat.

The H-Bridges function perfectly, and i have the sketch on the arduino programmed to only allow one polarity at a time from the h-bridges, so im not just shorting the batterys with the accidental press of a button.

Currently i only have $30 bucks to spend on parts, but i have most of the important components, and im getting the motors and possibly wheels for free from my geography teacher i had my freshman year at highschool. (he gets a lot of stuff from auctions and what not)

I would appreciate comments, concerns, and help. Im hoping to have this robot up and running (not literally running of course, but driving) in under a month.

Im good with circuits and whatnot, so dont be afraid i wont understand, and if there is something i dont understand, google is always a click away.



« Last Edit: July 30, 2011, 06:37:04 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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i really want to make sure the proper voltage gets supplied to the arduino and router. Once you let out all that factory installed smoke, its impossible to get it back in  ;D Trust me, i know, ive done it before, sometimes on purpose with a 9.8 joule 200 volt diy capicitor bank, sometimes on accident.
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline corrado33

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Re: 16 year old needs help building a robot
« Reply #2 on: July 30, 2011, 08:16:53 PM »
You seem to know what you're talking about.   :D

As for batteries?  It really depends.  If you want light batteries, go LiPo/LiB.  If you want normal rechargeable, go NiMH, if you need lots of current, go NiCd.  You're going to have to be able to recharge any of these, and a good charger is usually expensive. 

About supplying your board/motors.  You just need some power regulation.  Take the 12V in from the batteries, put a switch and a couple of fuses on it (before and after the switch).  Throw some capacitors on there and some kind of voltage regulator that can handle 1A, a couple of LEDs and you're done.  (Ok I way over simplified that).  Just google 5V regulator circuits. 

Here is a VERY simple one.  It probably won't work for you because of your current requirements, but you should be able to find replacement parts that fit the bill.  This is the basic design, you can add many more things to make it more efficient, better at filtering out noise etc. 

Oh, you'd also have to tap into the B+ and B- before the regulator and feed that directly to your motors. 




A question though, why the heck do your relays require 1A.  That seems like a lot...

Also, if you are on a strict budget, I think ordering your parts from Digikey or mouser would be a lot cheaper than radioshack.  I mean for crying out loud they have single LEDs for sale for like $2.  That's a terrible rip-off. 
« Last Edit: July 30, 2011, 08:18:26 PM by corrado33 »

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #3 on: July 30, 2011, 09:57:49 PM »
Hi,

Why use relays to switch relays?

Isn't the 7.5A grossly underrated? I haven't seen any cordless drill motors that didn't gobble up more than this in the start surge, when changing direction and when heavily loaded - and you want 4 of them to share this (i.e. ~1.9A each in the unlikely event that they share it equally).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #4 on: July 31, 2011, 01:08:40 PM »
the relays don't require 1 amp, but that's what I'm supplying to them, could go less, but that's all i could find at radioshack, But i guess i could use a old car cellphone charger, gut it for its regulator circuit, then i have a decent 5 volt output.

I'm not going to to print a PCB, I'm going to use a prefboad and some copper wire and make my own ghetto PCB (Ive done it before, its not as bad as it sounds xD)

the motors probably do suck more then 7.5 amps, but i don't have a good enough power supply to test there full amperage draw, and all i currently have in the realm of drill motors is just one motor, without the gear box (hopefully getting the motors soon)

Plus i only have a DVM and its rated at 10 amps unfused, And i do have a 9.5 amp 19 volt power source, but I'm not going to risk my DVM with that.

Once i get the motors ill make the final decision as to what regulator i should use for the motors.

A interesting idea presented itself to me earlier, What about using car window regulator motors, because i believe they have internal gearing that would allow me to directly connect them to the wheels. Probably harder to get car window regulator motors, but I'm curious as to if they suck less power then a drill motor, Because i need this to have some force behind it.

And yes i know radioshack is a rip off, But due to the sad fact I'm 16, i don't have a credit card yet, and my mom doesn't trust ordering things from the internet, i don't really have a choice. Because i don't want to ask someone else to order them, that's just putting a burden on them. Although i could go up to Sparky's Electronics, but they are miles away, And since i don't have a license, and my mom refuses to drive me there, I'm out of luck once again.

Also, while doing some testing of the Arduino's code, i have noticed that the sanity checks for only allowing one direction at a time are not working. Here is my code

Code: [Select]
#define DEBUG 0
#define WAIT_FOR_START 1

unsigned char incomingByte = 0;
unsigned long loop_count = 0;
unsigned char horn = 32;
unsigned char redLED = 64;
unsigned char BlueLED = 128;
unsigned char FireWeapon = 4;

unsigned char LeftForward = 1;
unsigned char LeftReverse = 2;
unsigned char RightForward = 4;
unsigned char RightReverse = 8;

unsigned char PORTB_val;
unsigned char PORTD_val;

unsigned char in_char = 0;

void setup()

{




//PORTD = digital IO 0-7
//FireWeapon, horn, redLED, BlueLED

  pinMode(4, OUTPUT);   // sets the digital pin as output
  pinMode(5, OUTPUT);      // sets the digital pin as output
  pinMode(6, OUTPUT);      // sets the digital pin as output
  pinMode(7, OUTPUT);      // sets the digital pin as output

//PORTB = digital IO 8 - 13  
//LeftForward, LeftReverse, RightForward, RightReverse

  pinMode(8, OUTPUT);      // sets the digital pin as output
  pinMode(9, OUTPUT);      // sets the digital pin as output
  pinMode(10, OUTPUT);     // sets the digital pin as output
  pinMode(11, OUTPUT);     // sets the digital pin as output
  
  Serial.begin(9600);      // set up Serial library at 9600 bps
  
  PORTD = redLED;   // turn on the red LED
  
  #if DEBUG
flash_led(3,500);
  #endif
  
  wait_for_start();  //Waits for startup message from router serial port
//continues after receiving it.
}


void flash_led(unsigned int count, unsigned int rate)
{
// debug routine that flashes an LED

 int n_count = 0;

 while (n_count < count)
 {
   n_count++;
   digitalWrite(13, HIGH);       // sets the LED on
   delay(rate);                  // waits for a bit
   digitalWrite(13, LOW);        // sets the LED off
   delay(rate);                  // waits for a bit
 }
}

char get_char()
{
//Function that waits for a character from the serial port
//If none are received, it returns 0.
//The timeout is so that if the router stops sending data to the microcontroller,
//the micrcontroller will stop driving the car, rather than just going forever with
//the last command.  Timeout is around 250mS.

  while (loop_count < 30000)
  {
    loop_count++;

    if (Serial.available() > 0)
    {
      incomingByte = Serial.read();
      loop_count = 0;
      return incomingByte;
    }
  }  
  
  loop_count = 0;
  
  #if DEBUG
        Serial.print('X', BYTE);
  #endif
  
  return 0;
}

unsigned char wait_for_start()
{
//Waits for startup message from router serial port
#if WAIT_FOR_START

  #if DEBUG
    Serial.println("Waiting...");
  #endif

  while(1)
  {
    if (get_char() == 'j' && get_char() == 'b' && get_char() == 'p' && get_char() == 'r' && get_char() == 'o')
  {
    
  #if DEBUG
      Serial.print("Start Code Recieved");
  #endif

      return 0;
    }
  }
#endif
}

void loop()  

{  
//Function that processes input from serial port and drives the Robot based
//on that input.

  in_char = get_char();
  
  //Split byte received in to upper and lower halves.
  PORTB_val = in_char & 0x0F;
  PORTD_val = in_char & 0xF0;
  
  //Make sure the BlueLED is turned on now.
  if ((PORTD_val & BlueLED) == 0)
  {
    PORTD_val = PORTD_val + BlueLED;          
  }
  
  //The following IF statements are sanity checks to make sure that LeftForward and LeftReverse cannot be on at the same time
  //and that RightForward and RightReverse can't be on at the same time.
  if ((PORTB_val & (RightForward + RightReverse)) == (RightForward + RightReverse))
  {    
    PORTB_val = PORTB_val - RightReverse;    
  }
  
  if ((PORTB_val & (LeftForward + LeftReverse)) == (LeftForward + LeftReverse))
  {
    PORTB_val = PORTB_val - LeftForward;
  }

  //Write the processed values to the ports.
  PORTD = PORTD_val;
  PORTB = PORTB_val;

  #if DEBUG
    Serial.print(PORTD, HEX);
    Serial.print(PORTB, HEX);
  #endif

}

the code isn't mine, its based from the code from the jbprojects site, and i edited it to fit my needs

(just ignore the "FireWeapon" parts, I'm considering adding either a potato cannon or a paintball gun to this when its complete., AND YES, YES IT DOES HAVE A HORN! just wanted to add it to make it beep xD)

and to answer the question as to why I'm using relays to switch relays is because if i have two relays wired in parallel and connected to a transistor (of course, i am using a diode across the relays coil leads) the relays will not actuate, the hum, and studder a little, but wont activate, plus i have over 50 relays laying around, mostly all of them are 5 volt for the coil. so it works best.

i was originally going to use the usual components to make the H-Bridge, but i soon realised i couldn't afford it. For crying out loud I'm using a old modified computer chassis as the chassis for this (maybe only temporarily, depends on how it works out )

the main concern i have is the amp draw from the motors, i would love to have some motors (with gearbox) that didnt suck too much amperage on startup, and under load, but still has the power a drill motor (with gearbox) has.

Once i figure out my motor situation, i will then deal with batteries, in the mean time, i can run the relays, microcontroller, and router off external power sources.

the main thing im worrying about, is powering the motors, while keeping a clean, 12 volt, noise free (as much as possible) power source to run the rest of the equipment off of.

« Last Edit: July 31, 2011, 01:19:05 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #5 on: July 31, 2011, 02:27:24 PM »
Hi,

What about using car window regulator motors, because i believe they have internal gearing that would allow me to directly connect them to the wheels. Probably harder to get car window regulator motors, but I'm curious as to if they suck less power then a drill motor, Because i need this to have some force behind it.
You could use window motors, but they'd be very slow, compared to drill motors.


Although i could go up to Sparky's Electronics, but they are miles away, And since i don't have a license, and my mom refuses to drive me there, I'm out of luck once again.
No bicycle?


Here is my code
[Snip]
Software questions are better posted to "Software".


and to answer the question as to why I'm using relays to switch relays is because if i have two relays wired in parallel and connected to a transistor (of course, i am using a diode across the relays coil leads) the relays will not actuate, the hum, and studder a little, but wont activate,
Wrong transistors or wrong application of them then.


i was originally going to use the usual components to make the H-Bridge, but i soon realised i couldn't afford it. For crying out loud I'm using a old modified computer chassis as the chassis for this (maybe only temporarily, depends on how it works out )
Relays are fine for an H-bridge and it only takes a single power MOSFET to make a relay H-bridge PWM'able (Could be added later, when you realize going full speed all the time isn't the best solution).


the main concern i have is the amp draw from the motors, i would love to have some motors (with gearbox) that didnt suck too much amperage on startup, and under load, but still has the power a drill motor (with gearbox) has.
Power in goes hand in hand with power out. Sure you can get less power hungry motors, but then you get less speed (given the same torque is assured by gearing).


the main thing im worrying about, is powering the motors, while keeping a clean, 12 volt, noise free (as much as possible) power source to run the rest of the equipment off of.
Why would you need a clean 12V?
Your controller will run on 5V and it's fairly easy to filter the supply when you have around 7V to drop.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #6 on: July 31, 2011, 02:40:55 PM »
Hello,

Yea, Window motors would be very slow, Its a though though.

yes i do have a bicycle, but Sparky's is about 15 miles away, in a bad part of town, a part of town i rather not be in.

I will post my code problem to software, i should of done that instead of posting it here, but i was thinking its probably something simple.

The transistors are not was i was orignally planning on using, i was originally planning on using 2n2222a transistors, but radioshack only had the mps2222a transistors, and i know from doing a little research, that it will work for one relay, never though to research its limits though.

Yes i know relays are fine for a h-bridge, but there are ways of making the h-bridge so much more compact, as in, not using relays that take up so much board space. and i knew going full speed all the time isnt the best, But i didnt know it would be so easy to make the H-Bridge speed variable, And now i must figure out how to implement that, and redo my controls setup to allow for it :)

And the motors, yea i know, it would be nice if it was possible though, it probably is possible with some sort of insane gearbox.. but that would be extremly expensive.

And the only thing im concerned about with having a clean power supply is that i know voltage fluctuations can damage the arduino, and even though there is a voltage regulator, i dont want the voltage to dip too low, but now that i think about the 7 volt drop the regulator would be doing, before it goes to the arduinos regulator, im not worried anymore.



Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #7 on: July 31, 2011, 02:48:39 PM »
after some quick googleing, i ran accross this
http://www.blog.oreind.com/wp-content/uploads/2010/03/pwm-speed-rotation-forard-reverse-and-regenerative-braking.jpg

i was wondering if this would work, based on the above link

« Last Edit: July 31, 2011, 03:14:15 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #8 on: July 31, 2011, 04:28:11 PM »
Hi,

yes i do have a bicycle, but Sparky's is about 15 miles away, in a bad part of town, a part of town i rather not be in.

Just bring brass knuckles - the exercise will do you good  ;D

Seriously, you could probably get them to send it to you COD or something.


Yes i know relays are fine for a h-bridge, but there are ways of making the h-bridge so much more compact, as in, not using relays that take up so much board space. and i knew going full speed all the time isnt the best, But i didnt know it would be so easy to make the H-Bridge speed variable, And now i must figure out how to implement that, and redo my controls setup to allow for it :)

You can get away with using 1 or 2 relays - Automotive relays would be well suited to the current you need.


after some quick googleing, i ran accross this
http://www.blog.oreind.com/wp-content/uploads/2010/03/pwm-speed-rotation-forard-reverse-and-regenerative-braking.jpg

i was wondering if this would work, based on the above link

There's no regenerative braking in that circuit and it's not very well designed IMO.

I have made a couple of simpler ones. The first one doesn't have a relay driver drawn in:

(Click for a higher resolution).

This a .pdf with a PCB layout. It is complete, besides missing a supply cap, as a good large cap will take up too much board space, so it is mounted "loose", directly over the supply terminals.
(Both circuits have been posted to this site at some time)

Only one DPDT (Double Pole Double Throw) relay is needed, as setting the PWM to zero stops the motor.
It may be hard finding a DPDT automotive relay though, but then two SPDT can be used in parallel.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #9 on: July 31, 2011, 06:15:54 PM »
So something like this? i added the transistor for



 
Hi,

yes i do have a bicycle, but Sparky's is about 15 miles away, in a bad part of town, a part of town i rather not be in.
Just bring brass knuckles - the exercise will do you good  ;D


Brass knuckles, yea that will work well, right up untill someone pulls a gun and blows me into the afterlife... I live in Fresno,Ca the gangs here wouldnt think twice about shooting me, hince why i stay away.
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #10 on: July 31, 2011, 10:52:05 PM »
Hi,

So something like this? i added the transistor for
Not quite (and I don't refer to the way you mangled the schematic making it hard to read).
If you swap the two leftmost resistors (2k2 and 150R) and place diodes over each relay - right at the terminals, it should work.


Brass knuckles, yea that will work well, right up untill someone pulls a gun and blows me into the afterlife... I live in Fresno,Ca the gangs here wouldnt think twice about shooting me, hince why i stay away.
Not that I want to urge you to go there, but how do you think the people working in the store survives?

Well, contact the shop then and explain that you're a minor and would therefore like to ask if you could buy some goods sent COD or by sending the amount in some way at the time of ordering. You may get lucky and all you can loose is the time spent on the phone.

Sparky Electronics, 4364 E. Ashlan Ave.
Phone: 559-227-2986
Fax: 559-227-0776
Email: [email protected]
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #11 on: August 01, 2011, 11:28:49 AM »
I will definitely contact sparkys and ask them about that, Also do you know any alternatives to the buzz11 ? Because it seems pretty hard to find. and out of curiosity i searched it on ebay, and there was only one listing, and it was like $6 per fet...

Also, is the mps2222A transistor a good alternativeto the 2n2222a ? i know i should just pull up the datasheets for them, but i was wondering if you had any personal experince using the mps2222a transistor instead of the 2n2222a
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #12 on: August 01, 2011, 02:28:20 PM »
cant find a alternative for the buz11 :(


Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #13 on: August 01, 2011, 04:02:27 PM »
Hi,

I will definitely contact sparkys and ask them about that, Also do you know any alternatives to the buzz11 ? Because it seems pretty hard to find. and out of curiosity i searched it on ebay, and there was only one listing, and it was like $6 per fet...

I went over Sparkys MOSFETS (very briefly) and if you find $6 high, you certainly ain't gonna like their MOSFET prices.

RS lists lots of useable alternatives, but only a few of them are in stock.
Some they should have in stock (and as such may be ordered in one off from one of your local RS shops):
http://www.alliedelec.com/search/productdetail.aspx?SKU=2731680
http://www.alliedelec.com/search/productdetail.aspx?SKU=9254040
http://www.alliedelec.com/search/productdetail.aspx?SKU=9250028

The most important numbers, in case you cannot get either of those are:
Max voltage (should be at least twice your drive voltage for a good safety margin).
Max continuous current (larger than what you expect the motors to draw worst case).
R_ds_on should be as low as possible, to minimize losses.

It should preferably be a Logic Level type, or at least be specified with a given R_ds_on or max cont. current within your needed range at a voltage of ~4.5V.
The lower the Q_g(s) the better, but this goes up when max current goes up and just need a bit more of the driver circuit to switch it fast.
The ones I have linked to should be up to the task and then some. If you cannot get some with a high enough current handling, two (or more) can be paralleled (if done properly).


Also, is the mps2222A transistor a good alternativeto the 2n2222a ? i know i should just pull up the datasheets for them, but i was wondering if you had any personal experince using the mps2222a transistor instead of the 2n2222a

Nope, we tend to use BC337 on this side of the pond, so you need to look that up yourself.


Edit: Just realized that I've been redirected to an Allied site (starting out at RS), but do ask RS on those anyway.
« Last Edit: August 01, 2011, 04:04:58 PM by Soeren »
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #14 on: August 04, 2011, 12:07:42 PM »
found someone that can order stuff from ebay for me, going to order some bc337 transisitors, found this http://cgi.ebay.com/100-x-BC337-BC337-25-TRANSISTOR-NPN-500MA-45V-PHILIPS-/320648922737?pt=LH_DefaultDomain_0&hash=item4aa82a4671#ht_1445wt_905

tell me what you think, i know there are 100 of them, but hey, i could use them over time :)

Also will the IRF510 mosfet work for the speed controller?
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #15 on: August 04, 2011, 12:23:03 PM »
also, do you think i might be able to get a mosfet from a old sharper image ionic breeze fan? i have one that is dead, and im sure that it has digital controls, so it might have a mosfet that may work, ill open it up and take a look. its cheaper gutting things for parts then it is to buy parts, so if you know of anything that has useable mosfets, please tell me



no mosfets in the fan, only transistors, ir reciever, leds, a "superchip" capicitors and resistors, a button board, a speaker, and a few diodes...
« Last Edit: August 04, 2011, 12:28:31 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

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Re: 16 year old needs help building a robot
« Reply #16 on: August 04, 2011, 12:34:17 PM »
check these out, tell ,me if any of these will work, i checked the datasheets and they look like they will work, but i want to get a professional oppion

http://cgi.ebay.com/New-50-pcs-IRFZ44N-IRFZ44-Transistor-MOSFET-N-Channel-/120688368352?pt=LH_DefaultDomain_0&hash=item1c19965ae0#ht_2404wt_1031


http://cgi.ebay.com/20-x-IRFZ44N-IRFZ44-MOSFET-N-Channel-49A-55V-/220816044652?pt=LH_DefaultDomain_0&hash=item3369a9726c#ht_1662wt_1031



and yes, bulk is better, that way if i mess up, i can redo it, also to build more in the future :)
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #17 on: August 04, 2011, 12:58:46 PM »
also if you have time, and if its not a hassle, search on ebay for a bulk sale for a compatible mosfet, at a low-ish price (as low as you can find preferablly) if you can only find one of like 10 pieces or so, thats fine
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #18 on: August 05, 2011, 02:32:13 PM »
Hi,

If you use the "Modify" link in a post of yours, you can add to it instead of making several posts and that makes it a lot easier to answer.

found someone that can order stuff from ebay for me, going to order some bc337 transisitors, found this [Snip link)
tell me what you think, i know there are 100 of them, but hey, i could use them over time :)
That's an OK deal and you might use them faster than you think.


Also will the IRF510 mosfet work for the speed controller?
No, they cannot handle anywhere near the current you need.


also, do you think i might be able to get a mosfet from a old sharper image ionic breeze fan? i have one that is dead, and im sure that it has digital controls, so it might have a mosfet that may work, ill open it up and take a look. its cheaper gutting things for parts then it is to buy parts, so if you know of anything that has useable mosfets, please tell me

no mosfets in the fan, only transistors, ir reciever, leds, a "superchip" capicitors and resistors, a button board, a speaker, and a few diodes...
First... A MOSFET is a transistor (MOSFET is an acronym fo Metal Oxide Semiconductor Field Effect Transistor)
This transistor you found, how did you determine that it isn't a MOSFET?
What is written on it?
Even if it turns out to be a "normal" (Bipolar) transistor it could be used, IF it can handle the current, but that's not very likely, as you will seldom find large components in a fairly low current device.

If you can find a discarded PC power supply, there should be both usable MOSFET's and high power Schottky diodes (plus coils that can be used in noise filters on the motor supply and a host of other components for later use).

Most devices that have moving parts (like a PC scanner, VCR's, Tape machines etc.) is worth stripping as well as most electronics build from the seventies to the nineties, as they have lots of through hole components. The newest units will mostly be containing surface mount devices and as such is probably outside your present abilities (but don't let that hold you back from taking a look inside).
Photo copiers and printers are full of mechanical parts you can use as well.

If you have room for it, don't spend a lot of time to completely rip a board - keep the entire boards for plucking whenever you need a particular component.


check these out, tell ,me if any of these will work, i checked the datasheets and they look like they will work, but i want to get a professional oppion
[Snip links]
and yes, bulk is better, that way if i mess up, i can redo it, also to build more in the future :)
Both links are the same IRFZ44 (the 20 piece had timed out) and they should do fine.
If you buy 50 of them (for the lowest price each) you can use them as is, or parallel two or more for larger currents. And they can be driven from a 5V supply if needs be.


also if you have time, and if its not a hassle, search on ebay for a bulk sale for a compatible mosfet, at a low-ish price (as low as you can find preferablly) if you can only find one of like 10 pieces or so, thats fine
If you got the smarts to build a robot, I'm sure you can handle your own eBay searches  ;)
Just go for the 50 IRFZ44, that's cheap at 40 cents a pop and you've got plenty for upcoming projects.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #19 on: August 05, 2011, 03:01:23 PM »
I googled the part number of the transistor, anyway i fixed the fan, using a motor from a old fan that had a broken blade, i also modified the firmware on the EEPROM chip to allow it to be controlled using a RCA remote  (because i didnt have the sharper image remote) i can now control my fan using my tv remote (tv remote is a universal remote, so its not like im contolling the tv and fan at the same time, that would just be silly) ^.^ which is pretty handy lol.



As for the SMD soldering, i solder surface mount components all the time, just need a heatsink so you dont fry the part, some thin solder, a well tinned, fine point soldering iron, and some solder rosin just in case, never had a problem, that was actually the first thing i learned how to solder, because what got me into soldering was back when i had my old gameboy, the charger failed and blew the smd fuse on the gameboy, i simply bought a new charger, and replaced the fuse with one from a old laptop harddrive :) all was good, and still is, i think i still have that gameboy somewhere.



The IRFZ44 Mosfets should be rather easy to find. And i do have a few desktop Power supplies, but they dont have there capicitors, took them out to make a coilgun xD it works,  i have a old printer, a couple dvd players, a sony blueray player with a corrupt firmware, 4 dead xbox 360 motherboards, a couple amps, boxes full of relays, switches, and LEDs, i even have like 20 solid state relays, some vcrs somewhere around the deep void of my bedroom, and i know have the control board from a 51 inch rear projection tv (the green tube on the tv failed, so i striped the tv for its useful components :P (speakers, tweeters, power supply board, wiring harness, control board, and amp board)  and i have the all important soldering pump to remove excess solder and to aid in removing components.

Things in my room have built up over time because i know i can use components from them, and i often do when i need resistors or LEDs, the ocasional battery compartment, or even wire. And old laptop motherboards i strip for all there compoenets and store them in a box :)
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #20 on: August 09, 2011, 09:30:57 PM »
i found some power mosfets on a tv power supply board, they are IRF1644G, i have been unable to find a datasheet for them, it seems like they dont exist!... but i built a circuit with on, and its not working... so yea... if you can find the datasheet for this fet, i would be happy, because i have a feeling that this fet isnt compatible...


there is always a output.... of 12 volts... and i dont know why..

im pretty sure its wired right... it must just be a non-compatible mosfet...

i want to make a working circuit out of scavenged parts before i order parts to make a final build... so i can test my code and what not

so far i have dissassembled 2 desktop power supplies, a vcr, tv powersupply board, all of the transistors and fets have given me false hope... after looking up there datasheet.. most of the parts are npn switching, pnp swithing, diode bridges, shunt regulators, and some other ones... kind of dissapointing.. but i now have a bunch of heatsinks for the mosfets :) i guess thats a plus

also, in the vcr.. which was sitting in my living room for years, there was a spider, so now i have a spider roaming around my room... oh fun.... it was on my arm earlier, tried to slap it off, it fell off, havent seen it since... little buggers....
« Last Edit: August 09, 2011, 10:59:42 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #21 on: August 11, 2011, 01:46:10 AM »
Hi,

i found some power mosfets on a tv power supply board, they are IRF1644G, i have been unable to find a datasheet for them, it seems like they dont exist!... but i built a circuit with on, and its not working... so yea... if you can find the datasheet for this fet, i would be happy, because i have a feeling that this fet isnt compatible...
They surely exists, as there are lots of vendors that wanna sell you some, but they cannot provide a datasheet. And they're guaranteed compatible, I just don't know with what ;D

When you get to such a component, you have 3 options:
- Save it for later (you might come across a datasheet or just the most vital data at a later date)
- Figure the pins out and test at a stepwise higher current - if you kill it in the process, you at least got some fun out of it.
- Toss it, life's too short for extensive testing  of maybe-good components (perhaps it doesn't feel so at your age, but at my age... Hey, I don't even slow dance anymore  ;D


there is always a output.... of 12 volts... and i dont know why..

im pretty sure its wired right... it must just be a non-compatible mosfet...
Or... A non compatible user  :P

How exactly did you wire it?

Most MOSFETs, when looking at the lettering, pins pointing down, has the pinout left to right: Source, Drain, Gate.
An N-channel device should be wired with Source to ground (0V), the Drain through some load (eg. a lamp or a motor w. reverse diode) to +V and the gate should have a resistor of say 10k to ground (I'd guess you forgot that one) to keep the gate low, as it is high impedance and will act as an antenna if not terminated. Touch it through a resistor of eg. 100 Ohm to some positive voltage (the +12V will do nicely).

A very few MOSFETs have a different pin out.
If it's a P-channel device, the Source goes to +V and the drain, through the load, to ground - the gate resistor is tied to +V and pulled to ground for activation.


so far i have dissassembled 2 desktop power supplies, a vcr, tv powersupply board, all of the transistors and fets have given me false hope... after looking up there datasheet.. most of the parts are npn switching, pnp swithing, diode bridges, shunt regulators, and some other ones... kind of dissapointing.. but i now have a bunch of heatsinks for the mosfets :) i guess thats a plus
You can test with bipolar transistors (of adequate rating) and change to MOSFETs at a later time.

You'll probably have found some dual diodes in a 3-pn TO-220 package (like a common voltage regulator). They can be used in parallel (usually you connect the outer pins) for quite substantial currents, are fast recovery types and usually with a low voltage drop. If the current  handling is large enough, a single of them can be used to protect the MOSFETs in both sides.


also, in the vcr.. which was sitting in my living room for years, there was a spider, so now i have a spider roaming around my room... oh fun.... it was on my arm earlier, tried to slap it off, it fell off, havent seen it since... little buggers....
It's hiding until you sleep - then it sneaks out and eats you as revenge... Muahaahahahaha
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #22 on: August 11, 2011, 09:54:11 AM »
i was going by the schematic you posted, maybe i am doing something wrong, i also found a k3067 mosfet, wired it up, to the exact same circuit, and on this one im not getting any output... very confusing... ill try putting a resistor on it, but if that doesnt work, then im either reading the schematic wrong, or something is wrong with the schematic...


i found the spider, and killed it when my ps3 controller xD... now i have to clean the controller... got spider guts on it...



Also i have been wondering what i should do with the 2 capicitors i have sitting on my desk, they are 250 volt 1000 microfarad capicitors, also i have about 12 200 volt 470 microfarad capicitors... if only i could find my capicitor chargeing circuit...
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #23 on: August 11, 2011, 04:55:34 PM »
Hi,


Quote from: myself
[...] If the current  handling is large enough, a single of them can be used to protect the MOSFETs in both sides.
Strike that, must have had my head in a jar, as it's usually the cathodes that are connected to the middle pin.


i was going by the schematic you posted, maybe i am doing something wrong,
What resistor values did you use?
Which pin did you connect where?


i also found a k3067 mosfet, wired it up, to the exact same circuit, and on this one im not getting any output... very confusing... ill try putting a resistor on it, but if that doesnt work, then im either reading the schematic wrong, or something is wrong with the schematic...
A transistor marked with a single letter followed by some numbers, like K3067 or eg. A, B, C or D insted of the K, is usually Japanese transistors and they have a prefix of 2S, which is rarely used in the marking, so the full name is 2Sk3067 (helps when you look for datasheets).
2SK3067 is a high voltage MOSFET (600V max), but very poor for your purpose with a R_ds_on of 4.2 Ω (typ.) and 2A max current on DC and 25W max.
It is far from a Logic Level device.
Even worse... It's one of the few MOSFETs with a different pinout: Gate, Drain and Source, which is the mirror image of most other MOSFETs.


iAlso i have been wondering what i should do with the 2 capicitors i have sitting on my desk, they are 250 volt 1000 microfarad capicitors, also i have about 12 200 volt 470 microfarad capicitors... if only i could find my capicitor chargeing circuit...
You could always use them in a lab supply, which really ought to be the first project for anybody starting out in electronics. unfortunately, I haven't seen such build as a starter, but it is way better with even the smallest variable supply, rather than duct taped D-cells :)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline aouate3Topic starter

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Re: 16 year old needs help building a robot
« Reply #24 on: August 11, 2011, 08:56:15 PM »
used this as my reference http://circuits.datasheetdir.com/97/IRF520-pinout.jpg

and used the attached image as my schematic.

also i have been feeding the pwm signal to the circuit using my computer's soundcard. and a pwm generator program.

so many transistors in the world... so many transistors in my room... what is it that none of them are what im looking for....
« Last Edit: August 11, 2011, 08:59:33 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

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Re: 16 year old needs help building a robot
« Reply #25 on: August 11, 2011, 09:00:44 PM »
looking at the schematic.. something seems odd... maybe the schottky... seems out of place...


also, for a variable power supply, all i need is a box full of various resistors and a few various low voltage wall wart power supplies... i have one that puts out only 1.5 volts! lol. i find that it is easier... because if i build a variable power supply... im just going to dissassemble it and use it for parts... then ill need it, and it wont be working... and ill be out of luck... so yea..
« Last Edit: August 11, 2011, 09:03:38 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

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Re: 16 year old needs help building a robot
« Reply #26 on: August 12, 2011, 11:53:47 AM »
since ill be using the circuit for testing, i guess i could just a npn transistor, for all that matters i could use a 5 volt motor because the circuit is for testing my code, and testing the concept before i purchase the parts.. but which npn transistor to choose...  a mps2222a should work in theroy, if it can switch fast enough...
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

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Re: 16 year old needs help building a robot
« Reply #27 on: August 12, 2011, 12:00:19 PM »
JUST RELIZED RADIOSHACK HAS THE TIP120 TRANSISTORS... 8amp max,  shouldnt that work fine?
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

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Re: 16 year old needs help building a robot
« Reply #28 on: August 12, 2011, 12:08:01 PM »
ok,  ill get 2 of the TIP120 transistors for switching relays for reverse, and 2 of the TIP42G transistors for pwm.

Do you think these are good choices? possibly for final board

or should i get 4 TIP120 transistors?
« Last Edit: August 12, 2011, 12:10:40 PM by aouate3 »
Been working with electronics since i was 2 (i was mostly taking them apart) around the age of 6 is when i started repairing electronics, ever since i have been fixing EVERYTHING, even pools and cars

Offline Soeren

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Re: 16 year old needs help building a robot
« Reply #29 on: August 13, 2011, 08:16:35 PM »
Hi,

First, I'll have to correct myself...
Most MOSFETs, when looking at the lettering, pins pointing down, has the pinout left to right: Source, Drain, Gate.
It's really like the one you posted: Gate, Drain Source - I'll spare you the ful history of how I early on was taught to read transistors and such looking at their backside and the influence of doing most protos in CAD probably have its influence as well.
(Who said sleep deprivation ;))


ok,  ill get 2 of the TIP120 transistors for switching relays for reverse, and 2 of the TIP42G transistors for pwm.

Do you think these are good choices? possibly for final board

or should i get 4 TIP120 transistors?
The PNP complementary to the TIP120 is the TP125.
As long as it's for testing software, it doesn't really matter - you can even use an LED replacing th motor for that too (LED will get brighter with a higher M/S ratio.

Personally I use TIP120/125 in selected circuits, but you need to be aware that a Darlington transistor have a relatively high voltage drop.
TIP120 can handle 5A continuous max. and with 5A draw, they'll have a voltage drop of up to 4V.
Those are 4V that the motor won't have any joy from and that's 20W of heat to get rid of.

You cannot compare TIP120's to the MOSFETs I have posted numbers for - they're totally different leagues.
Just take reasonable ESD precautions and make a simple circuit (eg. a 12V 20..25W automotive turns flasher lamp as load) and stick to it until it works. If you give up and take a completely different direction whenever you meet a hurdle, you'll never get to your goal. As long as you don't ruin them by static electricity, they're easy to get to work. Taking notes while experimenting is a good way to keep the focus and not keep trying the same mistakes over and over.


I asked you to use the "Modify" link on top of your posts, to keep your question in a single post, which is easier to answer - please do that, if you want answers on all of it - I don't wanna spend lots of time collecting from several posts, as this is time going from someone else, so onwards I'll answer one post at a time - you decide what to fill in it :)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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