noob qusetion. ive programmed a 16f84 and 16f628a to flash an led. they both flash in the programmer/experimentor.when i actually build the circuits on a bread board they dont work. any ideas whythis could be so.
pic problem
Feb 04, 2007
4 Replies
I'm assuming you've checked the power connections, and the LED isn't wired backwards; did you connect to the wrong port pin? Are any pins shorting?
Does the pic work when you put it back in the programmer? That will tell you if you blew the pic.
Assuming that all of the connections are proper you problem may be that the MCLR pin does not stay low before the power gets to full voltage. Be sure to have at least 10K on this lead to Vcc. An added cap, .1uf to gnd may also be helpful. Be sure that the power comes up fast. Slowly rising power may cause confusion with the MCLR voltage. There is a spec. on this.
do you have a power-on reset circuit for your pic? They can be funny about that - had the same thing with 84s myself which was poor POR
How long are your power leads? Long wires make inductance which results in slow power rise times. PICs are kinda funny about the rise time of the power, they want to see the voltage climb fairly quickly.
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