circuit_0.jpg (50038Bytes)
in an effort to learn about using the picaxe board, I'm trying to blink an LED on a new board. I think I've got it set up correctly (see pict). The + leg of LED goes to digital out pin 3, the neg side of leg is connected to 330 ohm resistor which then goes to a ground pin. The code I typed in is main: high 3 pause 1000 low 3 pause 1000 goto main. I downloaded the program to the board and nothing happens (no blinking led). When I pull out the connector to pin 3 and plug it into a V1 pin, the LED lights solid. Any suggestions what I'm doing wrong as far as getting it to blink. Thanks. I appreciate the help.
Try to connect the V+ lead
Try to connect the V+ lead from the LED to V+ trough the resistor and the ground to output 3 on the board.
further investigation
Thank you for the suggestion, Balderbraa, but no love there.
I pulled out the LED and put a meter on pin 3 and ground. I changed the time the pin received juice from 1 second to 6 seconds…high for 6, low for 6… and sure enough… the pin received .617 volts for 6 seconds… then 0 for 6 seconds… so it seems the board is cycling…however, .617 volts is not enough to light up the LED. Why would it be receiving such a low voltage? Is there some adjustment I would make somewhere? Thank you for the help. Am I thinking about this correctly?
FOLLOW UP: I tried the same with an arduino board (cycled on and off for 6 seconds… this gave time to get a voltage reading on the LED)… On the arduino pin, when high it pulled 2.26 volts… then off for 6 seconds… so why is the picaxe just pulling .617 volts on the pin???
Wrong direction
The meter should not go from pin 3 to ground, it should go to pin 3 and +. If you are using the darlington chip on the 28x board, you will be “switching ground”. When the darlington gets a high signal, it connects its output to ground --not Vdd. Test again with your meter, pin3 and +.
Same with your LED, positive goes to positive and negitive goes to the darlington output.
success
Chris… thanks once again. That worked! I hooked up the LED positive lead to V1 and the neg LED lead (with the resistor) to the pin 3. I thought (wrongly, I see), the ground pin would be neg and the output pin 3 would be +. I didn’t consider with pin running through the darlington chip… that would be ground.
With no resistor, it pulls 3.79 v and with the resistor to light the LED, pulls 1.79 volts. So… all is well. Thank you Chris.
I guess maybe this is what Balderbraa was alluding to… I just didn’t get it at the time. Thanks, both.
