High voltage hardware question

[mackrackit]

Hi,

For the power supply (3V) for the PIC, I am going from a voltage divider, to a regulator with a filter then to the PIC. For the digital inputs, they are going from the voltage divider directly into the PIC. I guess I am not sure if the input for the buzzer is causing the PIC to reset or if the buzzer is somehow feeding back into the regulator, which is causing it to reset.

Like Jerson said, a schematic would really help.

A big cap at the buzzer might help... but.

1- 3 volt regulator fed from voltage divider. Input voltage I would guess is higher than 5 volts?
2- Voltage divider directly feeding inputs. What is this voltage?
3- If the divider is set for 5 output with 74 input a spike would over volt the inputs, and if 5 volts is enough to run the regulator, a voltage drop would also drop the regulator out.

Try not connecting the inputs of the PIC. What happens? If works when the buzzer is on try clamping the inputs.

[Snap]

You could try and fix it in the software, Make the pic trigger with a known source and then wait a set period of time (eg 8ms) and see if the source is still there. DC spikes are only about 4 ms long and looking for a solid signal could help.
Snap

[Squibcakes]

Just a thought,

You say the buzzer has a big coil in it. Maybe you need a diode on the pic pin to supress any back emf from the buzzer?

Squib

[spuffock]

I have had some really horrible spike problems. A lot of them have been totally cured by fitting a 100n ceramic capacitor across the PIC's power pins, as close as you can get.
Hope this helps.

[GeoJoe]

Here is what I have done.
Bypassing, bypassing, bypassing. Make sure you have plenty of bypass capacitance on your pic power pins.
In really bad situations I have had to put a small inductor on the +5V line between the regulator and the pic.

Good luck

[mister_e]

Ground plane, ground/power routing, splitting power/digital/analog ground, PSU bypassing, PCB layout... tons of possibilities here.

Overloading PICoutput/PORT is still possible. The whole schematic and actual layout could be helpful.

[SOMRU]

Try adding an inexpensive small relay, or optocoupler, in parallel to the coil, then use the contacts as your signal source. Simple easy and I use this type of isolation in industrial welder controls.