ATtiny13 controlling 5v Relay Module - Not working with 5v pump output connected

Hi all.. trying to control a 5v relay module with an ATtiny13. Heres the key points, with a picture diagram included below

  • This is a 5v relay MODULE, not just a relay
  • ATtiny13 Pin 0 is HIGH output pin to control relay IN.
  • This setup works fine when the COM/NO is not connected on the output side (I can see the relay kick on at the proper specified intervals)

Once the COM and NO wires for the 5v pump are connected, the relay will just very briefly kick on for a few milliseconds, and reading the voltage of pin 0, it spikes up to ~~0.09 volts briefly.

Despite it being a relay module ive tried using NPN transistor, with ATtiny pin 0 controlling base and still nothing...

Any advice?

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if the pump is disconnected does the relay properly operate?

Yes that is correct, no pump and relay will switch on at proper interval for ATtiny13 code.

The pump may be too much of a load for the power supply. post a few images of the project.

I had this exact same setup running with an Arduino nano (and wanted to get my Arduino back and was trying to swap it for an ATtiny) - micro USB in to Arduino, and wire connected to 5v Arduino pin

Power source is a 5v 1.5A output box connected directly to the wall.

If thats not enough info let me know and i can clean it up for a picture

There is not a single capacitor in your circuit. There may be interference that restarts the microcontroller.

Post a link showing technical information on each of the hardware devices.

I think you may have nailed it with this here... im just getting back to messing around with this and when I tested a separate power source for control side of the relay it worked fine, going to try running it over a capacitor now..

ATtiny13 20U
5v DC pump (working voltage 3.3-5V)
5VDC Relay Module

I tried the exact same setup with A) separate power sources, and B) a DC-DC stepdown (without actually stepping down the power, using it as a power source isolator) and both of those worked... Im assuming I need to isolate the power in some way just not sure exactly how?

I had high hopes for the capacitor but it didnt seem to work :frowning:

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