Originally Posted by
cutting42
Hi Howard
My decoder build is progressing well and I have knocked up a couple of PT's as well and have a couple of questions before I take the PT to my local track on Thursday.
Is the LED supposed to come on with power or during operation?
Does the J1 pin 1 going to GP4 do anything or was it potentially a remote control feature?
Thanks
Originally Posted by
cutting42
Hmmm, not a peep from the PT at racing tonight. I have built up two and they both did not work. Any tips where to start fault finding Howard please?
I guess start with 5v supply then the signal from the crystal and track the PIC ip/op and gates.
My apologies for this delayed response!
J1 has no function at the moment.
Your troubleshooting plan sounds good. Check the supply first, then make sure the oscillator is running; its buffered output is at pin 11 of U1D, one of the XOR gates. Look for missing components or incorrect component values, and that the ICs and Zener are in the correct directions. If everything looks good there, you should see signals at pins 5 and 6 of the microprocessor, and at pins 6 and 8 of the XOR gates.
The LED should be on. If it isn't, then the microprocessor hasn't booted, or the LED is in backwards, or the resistor value is wrong.
Let us know what you find!