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I am using a 12V 5A adaptor to power a 12V pump and a 12V solenoid valve. The solenoid valve is supposed to pull 600mA, the pump is supposed to pull 0.6-1A. Hence to play safe the 12V 5A adaptor. Besides this I am also powering my Arduino with the same supply and a buck convertor converting to 5V in between. The Arduino is loaded not much, just a 16x2 LCD, a sensor drawing about 20mA, a relay module (single channel, not always live.)

I am seeing a voltage drop to 10V each time the pump and solenoid valve are powered. I was specifically advised that the ampere rating of the adaptor should be more than double the expected load to prevent a voltage drop, hence my 5A adaptor, but the voltage drop is still there, and the output of pump is going down. Now to my mind either the pump is dying or the adaptor was never fully alive as the flow through the pump has gone down. What is the issue here?

enter image description here

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    \$\begingroup\$ How long and what kind of cable do you have? Pumps etc often are at longer distance. \$\endgroup\$
    – jonathanjo
    Commented Nov 4, 2022 at 7:50
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    \$\begingroup\$ How long is the wire? Where are you measuring the 10V? A 2V drop across a long wire at 1A+ isn't that surprising. Measure the resistance of the wire to be sure. \$\endgroup\$
    – Puffafish
    Commented Nov 4, 2022 at 7:53
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    \$\begingroup\$ In my experience. "No datasheet" = "Expect surprises" :-) \$\endgroup\$
    – jonathanjo
    Commented Nov 4, 2022 at 7:59
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    \$\begingroup\$ Do not use breadboard side rails to take amps of current, there's your voltage drop. \$\endgroup\$
    – Neil_UK
    Commented Nov 4, 2022 at 7:59
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    \$\begingroup\$ Put a 1000uF electrolyte cap on the supply input of your board. Oh and do not use breadboards at all, for any purpose. It is useless trash. Solder all components. \$\endgroup\$
    – Lundin
    Commented Nov 4, 2022 at 7:59

1 Answer 1

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I am feeding the supply from the adaptor into a breadboard side rails, and from the siderails to the adaptor. I am measuring the voltage in the siderails.

There's your problem. The rails of a solderless breadboard aren't made to carry high current.

The sockets have relatively high resistance and the rails themselves aren't very thick - and they aren't made of copper.

As far as the pump is concerned, your breadboard is essentially a resistor between it and the power supply.

Wire the pump directly to the relay and the power supply instead of running it through the breadboard.

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  • \$\begingroup\$ aha, could never have thought of that, thanks...will solder everything...if the problem persists then will write again... \$\endgroup\$
    – DribbleNibble
    Commented Nov 4, 2022 at 8:03
  • \$\begingroup\$ hey, I soldered everything, but the voltage drop is still there, and my pump's flow rate is consistently decreasing, like its on its deathbed \$\endgroup\$
    – DribbleNibble
    Commented Nov 4, 2022 at 10:26

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