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After correcting the false triggering I was getting in my last question:

DSLR Hotshoe revisited

It was related to debouncing the pulse sent from the camera to the flash, I noticed one more problem.

I built this circuit below to detect my Canon flash firing. Everytime I power the circuit off, the flash always fires.

Flash to Arduino Circuit

The circuit is powered by a battery that supplies both the camera flash (with a DC/DC buck converter inside the flash) and the Arduino.

How can I adapt it in order to, if the supply is cut, the flash wouldn't fire?

I was thinking of using a P Channel Mosfet on the Arduino side, but I'm not sure on how to implement it safely, to not do something wrong with the flash or camera.

Complete schematics added for better understanding below. Schematics

Rodrigo
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  • I see a connection for a camera. I see a connection for an Arduino. I don't see a connection for a flash. What's the flash connected to? "*Everytime I power the circuit off, the flash always fires.*" What exactly are you powering off? Vcc or the Arduino or both? – Transistor Apr 01 '21 at 19:27
  • @Transistor The connection for the camera (Trigger contact) is the same for the flash. They touch each other when the flash is attached. I actually soldered three wires inside the flash (trigger, GND, and VIN) VIN inside the flash powers a DC/DC buck converter from 7.4V to 3V the flash needs). The Trigger wire goes to the arduino. When I power the 7.4V battery off, I disconnect all supplies from both flash and Arduino . Arduino is powered in VIN, from 7.4V. – Rodrigo Apr 01 '21 at 19:50
  • Why not turn off power source to flash only and then later turn off power to Digispark only? Then you can see if powering off Digispark causes trigger signal or just powering off flash. – Ernesto Apr 02 '21 at 05:26

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