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Bad outputs while programming

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jrz126

jrz126

Active Member
I'm working on a product tester for work. I need to control 20 relays plus a bunch of other I/O. I'm using an 18f4520. To save IO pins, I have my relays controlled using 3 74hc299 shift regs which control some uln2803 transistor arrays.

When I program the chip, I get some bad data on the shift reg. control pins, causing my relays to turn on/off somewhat randomly.

I've attached the schematic of the relay portion. I'm using a pickit 2 to program it.
 

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