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Topic: Reset occurs the first time a reed relay is powered up using Nano Every program (Read 794 times) previous topic - next topic


I'd agree with the previous , but also add- does the problem still occur if the relay is removed ?


I have the "-" side of the relay soldered directly to the Arduino's GND, and the "+" side of the relay soldered directly to a digital output pin (no wires are used)
The "+" side of the relay needs to be connected to +5V, not an output pin. As you have it connected, some of the coils "flyback" energy gets injected straight into the MCU, therefore it locks up. Use the "-" side of the relay to control it from your output pin (LOW turns it on, HIGH turns it off).


So long as the + side is positive and - side negative, it doesn't matter.

You can have + going to 5V and - to the Arduino pin,
you can have - going to GND and + the the Arduino pin.

The diode will work the same in either case, preventing inductive kick back but normally just sitting

If you connect the wrong way the diode will short the pin's output which is bad for the pin and may overwhelm
the supply as well, causing a reset.

But none of this seems to be the actual problem.  I would double check the wiring of the reed relay to
ensure the coil side of it isn't shorted to the contact pins, and use a multimeter to check the isolation
between coil pins and contact pins too.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


In my opinion, connected as a low side driver is more desirable. The clamped backemf is positive (+5.7V) and tied to VCC. Connected as a high side driver, the clamped backemf is negative (-0.7V) and tries to pull GND lower ... this negative signal travels into the MCU in a sensitive area (the I/O protection and peripheral).


Can you post a copy of your schematic please?
Can you post a picture of your project please?

Is you project on a PCB or on breadboard/protoboard?
How are you powering your project?
Have you tried replacing the relay coil with a 470R resistor?

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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