Author Topic: new to electronics and engineering, need help  (Read 3618 times)

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Offline extreme.alyTopic starter

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new to electronics and engineering, need help
« on: July 29, 2008, 04:01:02 PM »
hello, as i said, i'm a beginner, i have a lots of questions to ask..

first is, i have seena lots of robots that moves their hands, legs, etc etc.. how do they do it in such a small space?? i mean what motor do they use it? is it servo? but servo is too big... or is it a stepper motor?
second, how can i make axle of a car? i mean, how do i make the tires to turn left or right? well i dont want the one reverse and one forward method...any samples of mechanics?

today i have bought my first microprocessor (atmega8) and im very excited to make sumthing awsumm!

thanks! :)

Offline izua

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Re: new to electronics and engineering, need help
« Reply #1 on: July 29, 2008, 04:11:22 PM »
do you have a programmer for the atmega?
mechanics shouldn't be your first concern.
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #2 on: July 30, 2008, 01:57:17 AM »
oh eah i forgot to ask that main question but i have a bit information about it... i'll connect MOSI/MISO/SCK/RESET, also the VCC pin and GND pins to the serial port and program with PonyProg.. am i right? will that do it?

Offline izua

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Re: new to electronics and engineering, need help
« Reply #3 on: July 30, 2008, 09:03:32 AM »
Yes. You connect programmer's MISO to atmega's MISO, and so on. then you must add a clock source to your atmega (by default it works with internal clock).
Anyway, fix an objective and try to focus on that.

to get that much power in such a small space you genneraly use BLDC motors or solenoids. Servos are also a good choice, but for such high powers they are not small.

To make an axle turn left/right, you will need to let the axle itself spin in a bearing, and rotate the bearing left/right with a servo.
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #4 on: July 30, 2008, 09:46:11 AM »
The internal clock of ATmega8 is 8Mhz, right?

few more questions:
I have seen in different schematics, people has connected leds in different manner to microcontroller... some of the orders are like this:
Microcontroller Output Pin > resistor > led > ground
Microcontroller Output Pin > led > reesistor > VCC (i didnt get that, how vcc comes here??)

tell me the advantage of adding a resistor to leds, push buttons, etc
and tell me the effects of putting resistors in these orders (told above)

one more, in the 50$ robot, where do I use the 340ohm resistor and where do i use the 1.62Kohm resistor? and which one is better for leds?

Offline izua

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Re: new to electronics and engineering, need help
« Reply #5 on: July 30, 2008, 10:21:53 AM »
depends on your microcontroller. i never worked with atmega 8. it's either 1 or 8MHz.
anyway, the logic with leds is that it needs +5 and gnd to work.

if you tie the kathode leg to ground, you need to supply +5 from your microcontroller.
if you tie the anode leg to v+, you must supply ground from your microcontroller. to turn off the led, you must send +5 (logic 1) on the pin. this is called inverted logic. remember, you can't tie the kathode to v+, or the anode to ground, the led is polarised. the kathode has a shoter pin, or it's not round (if the led package is round, you will notice it's flat). the interior usually has a larger metallic-looking piece.

there's a whole theory on buttons, since you need a pullup/pulldown, debounce routines, etc.
the simplest way is to connect your button to ground, one pin, and an atmega at the other pin. enable the internal pullup in the atmega. the pullup will keep the pin high. when you press the button, the pin will read low (ground).


I'm not sure about the resistors, since I never built the $50 robot. I wouldn't put a 1.62K resistor on a led, since it won't shine very much.
« Last Edit: July 30, 2008, 10:24:00 AM by izua »
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Offline krich

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Re: new to electronics and engineering, need help
« Reply #6 on: July 30, 2008, 12:24:54 PM »
The 340 resistor is used for the LED on the $50 robot project.  I forget what the other is used for, but the 340 is definitely for the LED.  You will be able to see why if you take a look at the LED Tutorial on this site.


Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #7 on: July 30, 2008, 12:59:48 PM »
then 1.62Kohm would be for RESET pin...

about the LEDs again, as you said, if i tie anode to v+, i have to provide ground to cathode from MCU and i cannot tie cathode to v+ & anode to ground...
so i can do this: anode to MCU giving 5+ (logic 1) and cathode to ground.. right?
« Last Edit: July 30, 2008, 01:05:49 PM by extreme.aly »

Offline izua

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Re: new to electronics and engineering, need help
« Reply #8 on: July 30, 2008, 02:38:32 PM »
Yes, and the led will always be on that way.
Now, if you tie the cathode to a MCU pin, when that pin will be 0, the led will turn on. When it will be 1, it will be off (no potential difference between 5v and 5v).
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #9 on: July 30, 2008, 03:41:24 PM »
one more quesstion, whats the difference between an electrolytic and ceramic capacitor?? i bought a ceramic 0.1uF ceramic cap... its written 104 over it but in the pcture of 50$ robot, its written 101 over it..whats the difference?

Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #10 on: July 30, 2008, 03:53:24 PM »
can i use electrolytic cap in both sides of the regulator? i mean before input and after output? i have bought only 0.1uF ceramic cap... forgot to buy the 220uF electrolytic cap...
if i can use elecrolytic cap in both the sides, which one do i use after output? the same 0.1 uF in electrolytic? or some other?
FYI, i'll be using 220uF electrolytic before input...

Offline extreme.alyTopic starter

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Re: new to electronics and engineering, need help
« Reply #11 on: July 31, 2008, 02:40:52 AM »
please i need an answer for the above question... without it i cannot proceed from power supply issue
just tell me which caps do i use before output and after input!

AND THANKYOU VERY VERY MUCH for your help!! i really apreciated it! :)
« Last Edit: July 31, 2008, 02:41:30 AM by extreme.aly »

Offline Admin

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Re: new to electronics and engineering, need help
« Reply #12 on: August 02, 2008, 05:51:11 PM »
The 1.62Kohm is for the photoresistors, but you can also use it on the reset pin.

Quote
i bought a ceramic 0.1uF ceramic cap... its written 104 over it but in the pcture of 50$ robot, its written 101 over it..whats the difference?

http://members.aol.com/shephed/caps.htm

Offline kd5kfl

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