MDBT42Q and 5v water pump

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Gordon

So by the look of it you're saying that if you connect a LED across the wires, you can control and LED using D18 as expected? Just not the pump?

Also as @allObjects says, what happened in the final picture D18=1, LED removed? In that case, what's the actual voltage across the voltage input? Is it still 5V?

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michael_101 in reply to @Gordon
Hi,

Thank you @Gordon and @allObjects for your detailed answers I learned a lot from them and sorry for the delay.
I am a software developer and I am new in all electronics thing.. so thank you for your patience with me ;)

I got it to work, apparently all 5 FETs I had were not good.

I did the tests as you asked me with this results:

D18=1:
- (D18 pin / Gate of FET) with GRD => ~3.3V
- (Drain of FET) with GRD => 5V
D18=0:
- (D18 pin / Gate of FET) with GRD => 0V
- (Drain of FET) with GRD => 5V
About the current measurement from FET Drain:
- D18=1 => 0A
- D18=0 => 0A
So I bought 25 new same FETs and I did the same test (20% of them were not good too).
The good ones worked fine with same results, except the current measurement that was ~100mA, and the FET Drain was ~8mV when D18=1

Thanks again.
Michael.

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