18f242 reset

[Andy Wood]

Bob,

Thanks for the reply. I do have a cap across +5 and Gnd. The program is simply

High PortC.1
YR:
Low PortC.1
High PortC.2
Pause 700
Low PortC.2
Pause 700
goto YR

I do have the WDT enabled

It will generally run for about 5 minutes, but sometimes only a few cycles, and resets to High PortC.1.

I am using a 7805 regulator, well filtered.
I have been working on the theroy that the power supply is dropping out, but it always appears to be at full power.

Thanks

Do you have a diode across the relay coil to suppress the back emf? If not, the "spike" when the relay is switched off could be causing the pic to reset.

Andy

[Armadus]

Andy,

There is a diode accross the relay.

Thanks

[mackrackit]

Try replacing the transistor with a LED and a 470 ohm resistor to make sure it is not something to do with the transistor or relay.

Is the cap across power rails large enough for BOR fuse. Rule of thumb, LED with resistor across power rails should go dim not instant off when power is cut.

What have you done with MCLR?

[Armadus]

Dave,

1. I have replaced the transistor and relay, but made no difference. I will try the resistor and LED you suggested.

2. I have a 330uF cap between the output of the regulator and Gnd.

3. MCLR pin is connected to +5 via a 4.7K series resistor, and a 0.1uF cap to gnd.

Thanks

[mackrackit]

One more thing if the other does not get it. Tie all un-used pins to ground with a 10k or so. If there is "noise" could have something to do with it. Good to do this on finished projects.