Driving vfd Grand Central chip gets hot

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enauman
 
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Driving vfd Grand Central chip gets hot

Post by enauman »

I've used Teensy microcontrollers to program salvaged vacuum fluorescent displays many times, driving them with ULN2803 Darlington arrays and driving the filament either directly off the 3V or with 4 GPIO pins and an h-bridge. Teensys being scarce these days I thought I could make a vfd shield to place on a Grand Central Express M4 but as soon as I upload Arduino code connecting any pins to the transistor arrays the processor gets hot, a little hot to the touch with a couple grid and segment pins, and overheats quickly with all of them. The 20V to the segment and grid pins (with 47k resistors) is provided from a buck booster powered from the GC 5V, which is also how I do it with Teensys. Can anyone see why the GC would be overheating like this?
Thanks!

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adafruit_support_mike
 
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Re: Driving vfd Grand Central chip gets hot

Post by adafruit_support_mike »

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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enauman
 
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Re: Driving vfd Grand Central chip gets hot

Post by enauman »

Oh geez, I put the Darlington arrays in backwards...

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adafruit_support_mike
 
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Re: Driving vfd Grand Central chip gets hot

Post by adafruit_support_mike »

Ah.. that will do it.

You're probably sending current through the input protection diodes on the ULN2803 pins. Hopefully that won't translate to any long-term damage to the Grand Central.

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