jumbleboy
Computer
- Jul 10, 2014
- 1
Hello
I'd be very grateful for some help on a problem we are having with a circuit board. The circuit is a PIC12F675 based temperature control board. The circuit uses a capacitor power supply to provide the power. The PIC reads a thermistor and triggers a triac when the elements need heating. It all works fine, but we are having a high failure rate on the indicator LEDs. After a while they start to flicker erratically and then soon after stop working altogether.
The 4 LEDs are in series, and when I test them with an external power supply they all still work, but one will draw around double the current of the other 3. This is enough to pull the voltage down making the LEDs flicker, though the PIC still runs happily. I have tried testing the boards on a continuous flash for days, and have tried to see if turning the circuit on and off many times will trigger the problem, without success. Does anyone have any idea of what we could do to solve this problem?
The PCB design is here -
and LED specs here -
Thank you very much
JB
I'd be very grateful for some help on a problem we are having with a circuit board. The circuit is a PIC12F675 based temperature control board. The circuit uses a capacitor power supply to provide the power. The PIC reads a thermistor and triggers a triac when the elements need heating. It all works fine, but we are having a high failure rate on the indicator LEDs. After a while they start to flicker erratically and then soon after stop working altogether.
The 4 LEDs are in series, and when I test them with an external power supply they all still work, but one will draw around double the current of the other 3. This is enough to pull the voltage down making the LEDs flicker, though the PIC still runs happily. I have tried testing the boards on a continuous flash for days, and have tried to see if turning the circuit on and off many times will trigger the problem, without success. Does anyone have any idea of what we could do to solve this problem?
The PCB design is here -
and LED specs here -
Thank you very much
JB