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11
Electronics / battery pack charger - DIY
« Last post by washb0ard on July 18, 2014, 09:41:17 AM »
I am trying to make my own charger for 6v/2000mah ternergy.
I only have a 5V/1A charger to make it. I think it should be ok, can anyone please let me know if that will work.
Thanks
12
Mechanics and Construction / Microphonestand-robot
« Last post by Gededyr on July 18, 2014, 06:19:27 AM »
Hi. I'm new here, and have never build a robot, but I'm good with electronics and soon educated electro-mechanic (don't know the title in english).
Also I'm an audio engineer and i'm constantly ripping my hair off when I record electric guitars because I have to run from the control-room to the recording room every time I need to place the microphone a cm to capture the best sound.
I saw an other engineer that had build a microphone-robot.. A micophone stand that stood ontop of a little table that could moove to the front, back and to the sides, and something like that is exactly what I need.

How do I build something that can hold a microphone and moove it around a little, so I can moove the microphone from the control-room?
13
Misc / A medium rang programmable robotic arm for mobile document capture
« Last post by mmluqman on July 18, 2014, 03:25:18 AM »
Dear all,

I am looking for a medium range programmable robotic arm for mobile document capture. To better understand the context please see the following:

1. I manually make the robot hold the mobile phone
2. I program precise angles (6 DoF) to simulate various orientations and rotations of human arm
3. In a second scenario I program the motion to simulate a human capturing a video of a paper document by moving the mobile phone over the document.

Could you kindly direct me to some interesting programmable robotic arms models/manufacturers available over the internet.

sincerely,
--Dr. Luqman


14
Electronics / Re: 50$ robot - Led supposed to light up??
« Last post by jkerns on July 17, 2014, 07:16:46 AM »
Per the diagram, http://www.societyofrobots.com/images/sbs_avr_schematic.png the LED goes between PD4 and VCC, so to turn the LED on you need to set PD4 low.

From the code (SoR_Utils.h):

void LED_on(void)
   {
   PORT_OFF(PORTD, 4);//turn LED on
   }
void LED_off(void)
   {
   PORT_ON(PORTD, 4);//turn LED off
   }

The function LED_on uses PORT_OFF  which is:

#define PORT_ON( port_letter, number )         port_letter |= (1<<number)
#define PORT_OFF( port_letter, number )         port_letter &= ~(1<<number)

and results in PORTD pin 4 going low which should turn the LED on.

So, to turn the LED on, you would call LED_on.

I have not used the pony prog so no help on that.
15
Mechanics and Construction / Re: CNC router VS 3D printer
« Last post by CJAlbertson on July 16, 2014, 09:05:47 PM »
Hey, I am a 13 year old robot maker and I want to know which tool is better for me. right now I do my robots by hand in a band saw and with my drill press. I want to buy something around $1000-$1500 and I was thinking of a 3d printer or a CNC router. I need some hlep and tips to decide.

The 3D printer will do a LOT mrs then a router.  It can make very complex parts.   But do NOT buy a 3D printer until AFTER you have proved to yourself you can design parts.  Simply send the STL file off to a service and then after you are making quite a few of them and like the results buy the printers   This lets you learn what kind of a printer you want.   What kind of materials work best and what sizes and precision do you need.  Figure this out using Shapeways or the like
16
Electronics / Re: 50$ robot - Led supposed to light up??
« Last post by washb0ard on July 16, 2014, 06:48:45 PM »
The reason I am trying to get my led to light up is because i am trying to trobleshoot. I get a WRITE FAILED from pony prog but my robot is doing something(always turning to the right) also Led never lights up.
17
Electronics / 50$ robot - Led supposed to light up??
« Last post by washb0ard on July 16, 2014, 05:31:23 PM »
Hello all,

 I see the below piece of code in the photovore_v1.c.. And based on how the Led is wired up in the pcb. I am confused whether it is supposed to glow when LED_off is called, can someone please explain?

 I feel that when LED_on is called a digital is in output on the pin DP4 which is connected to the negative of LED and the positive of LED is connected to 5V(Vcc). Since there is no potential difference iam not sure if it supposed to glow

Code:
        configure_ports(); // configure which ports are analog, digital, etc.
   
   a2dInit(); // initialize analog to digital converter (ADC)
   a2dSetPrescaler(ADC_PRESCALE_DIV32); // configure ADC scaling
   a2dSetReference(ADC_REFERENCE_AVCC); // configure ADC reference voltage

   /*********ADD YOUR CODE BELOW THIS LINE **********/
   delay_cycles(500);//a small delay to prevent crazy oscillations
   LED_off();//turn LED on

18
Software / Re: Problems uploading to Axon II using McUber
« Last post by Hero I on July 15, 2014, 03:48:25 PM »
Did you install the USB drivers, and does your PC properly recognize that the Axon is plugged in?

Yes and yes.
19
Mechanics and Construction / Re: bandwidth of two wheel inverted pendulum
« Last post by Billy on July 14, 2014, 11:09:12 PM »
As for using a physical filter at the output of the accelerometer, I would suggest going with a digital filter instead, such as an IIR.

He/she needs an anti-aliasing filter. That is always physical. The IIR or FIR can be used for tuning.

Everything else you said was spot-on!
Late to conversation. My apologies.
20
Electronics / Re: Servo Problems
« Last post by Billy on July 14, 2014, 10:59:12 PM »
what do you mean by  isolation or the servo pulses being irregular(do you mean the servos might be the problem)?


Isolation is a means to leave two circuits unconnected electrically, but allow for information (signals) to pass from one circuit to another. There are several types but include using light to send signals in an optocoupler (optoisolator), or to use magnetic field in a signal transformer or digital isolator. I have even seen a large 50 Hz 3 phase power source isolated from the 60 Hz 3 phase power supply by using a large motor to turn a large generator. In that case the signal was mechanically transmitted.
Here is a link you should have read prior to posting your question, but I'll you slide by on this one: http://en.wikipedia.org/wiki/Galvanic_isolation
It's not the best wiki page I have seen but least they took the time to include diagrams.

Your cell phone allows your parents to send a text saying to come home without you having to actually see your parents, so that would be called social isolator.  Angry mom or happy mom, all you see is the words sent by mom. You don't see the upset look on her face because you're late for dinner AGAIN! You only get the clear, quiet, no-attitude message to come home.  Same with electrical isolation; you get the signal without the electrical noise that is on the other circuit. Angry circuit or happy circuit, you only get the message sent.  Motor (servo) circuits can be noisy (angry) and that noise interferes with the communication between uCs (mom) and other electrical parts (you).

My comment on the pulses being irregular meant simply that the pulses from the uC may not be the same distance apart or not the correct width every time the uC sends one. Maybe your SW is thinking about something else when it should be thinking about sending pulses.

I don't know anything about Ardinos so do not know how the pulse trains are generated. If they are generated by flipping bits in an interrupt routine then maybe you're taking too long in the interrupt and missing the start of the next scheduled call, or maybe you're modifying a variable that gets used in the interrupt when the interrupt gets called, so it's not the value you want it to be. Can't help you there.
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