chips occasionally blowing?

[mister_e]

Let's do a guess from what i can understand of it. Are you really sending your PIC i/o directly to the base of your TIP122 without any resistor in serie with the base? if so... your problem is there.

Also, as those transistor have already resistor between base and emitter.. you don't really need those you place.

If you don't want to do PCB modification, you change your TIP122 to a mosfet, some, see all, Logic type can be driven without resistor in serie with the Gate.

[kenpo]

here's the thing, the circuit has alot of ports, like for the tip122s, but they're not being used as of yet, only ONE of the 19 boards I used a tip122, and that one hasn't blown, it's perfectly fine... which is odd,( I'll obvisoly add the resister as you suggested though for the next revision, I have no qulams about redesigning and reprinting the board. I need to make more anyways).

what's being driven from the pic is the mac floppy motor, and the counter chip.
so the circuit isn't really as complicated as it has space for, there's really only like 4 things on it usually.

I'm wondering if I need to some how buffer the incoming voltage??? is the 5v clean enough? should there be a resitor somewhere for the pic voltage incoming or outgoing... I mean, really, all I cna think of (other than the tip problem, which hasn't been the source yet) is that the mac floppy needs a diode on the signal pin, perhaps theres feedback being thrown back to the pic? I send a HIGH pulse for 800 (pause) then the motoer does a rotation once around.

and running the 16f628a on internal clock, is this bad? I'm wondering if I've hooked in one of the traces to the pic wrong or something....

also, a few osc crystals blew, but I've heard that can happen alot...? so i started using the 628 to avoid external clocks

[kenpo]

here's the tiny circuit for the counter chip. 2 leads from the pic, one to make it count forwards, one to reset (though I never got the chip to reset for some reason)
and 5 led spots, one resitor as only one led is on at once. easy to understand, bare bones.


could the motor someho introduce noise (or soemthing, I'm not an engineer) into the power supply?

[NavMicroSystems]

OK,

based on your "Artworks" I can tell:

The problem is with the black track.

For best results you should always design PCBs without having a proper schematic first.
That way there is only little risk for a real surprise.
(The rare occasion that it works)

You should have a look at EAGLE

[Ron Marcus]

<OK,

based on your "Artworks" I can tell:

The problem is with the black track.>

It could also be the rectangular pads...Surface accoustical wave heating?
Don't be dissin' Eagle
Can we add PTFS to RTFM?