Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: jambot on August 10, 2010, 10:00:55 AM

Title: $50 Robot LED and Circuit Testing
Post by: jambot on August 10, 2010, 10:00:55 AM

Hello,

I have a question with the $50 robot circuit - the LED does not light when the microcontroller is installed and 7 V is connected, and I have no voltage across the VCC and the PD4 pin.  Should the LED light when voltage is applied to the finished circuit before programming?

I have checked the following with my circuit:
-All connections seem to be correct when I checked with a voltmeter.
-I have 4.95 V on the microcontroller circuit past the regulator.
-The LED lights when 7V is applied directly to the LED sub-circuit without the microcontroller installed. The LED circuit between VCC and PD4 is good and has a ~ 1V drop.
- The LED is installed correctly with the positive end on the VCC side.

Do I need to wait until it is programmed to have a voltage across PD4 and VCC?

Thank you in advance!

Title: Re: $50 Robot LED and Circuit Testing
Post by: waltr on August 10, 2010, 10:36:45 AM

Quote

Do I need to wait until it is programmed to have a voltage across PD4 and VCC?

Yes. The LED is controlled by the code and will light when port PD4 is set-up and written to.

You should measure about 5V on Vcc to ground without the processor.

Title: Re: $50 Robot LED and Circuit Testing
Post by: jambot on August 10, 2010, 05:17:29 PM

Thanks waltr.  I am glad to know that my circuit might be all right.  I couldn't find another post that answered this clearly.