beginner: will 1.4A flow through a 1N4001 diode?

In a thread from 24.Aug.2008 called "beginner: hopefully simple question about regulators", I asked for help on how to power a 12VDC 1.4A pump. The kindest answer was: connect 2 (or maybe 3, to overcome motor start-up surge) 800mA wall adapters in parallel. And thank you.

Due to holidays/weather, I forgot one last question. As a month has elapsed, I hope opening a new thread is okay etiquette.

See attached circuit. This circuit will lie between the wall adapters and the pump. Once the pump is on, it may stay on for several hours. Should I upgrade any components? Specifically, I rather suspect all 1.4A will flow through the 1N4001 diode. But the 1N4001 datasheet mentions an Average Rectified Forward Current of 1A. I'm not quite sure what that means.

Thanks very much for your help.

There is nothing wrong with that, look at the datasheet, it can happily take 50A short periods of time so 1.4A should be no problem.

Also, the diode is normally not conducting. It is a protection diode for when the motor current is switched off.

nyoo said:

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See attached circuit. This circuit will lie between the wall adapters and the pump. Once the pump is on, it may stay on for several hours. Should I upgrade any components? Specifically, I rather suspect all 1.4A will flow through the 1N4001 diode. But the 1N4001 datasheet mentions an Average Rectified Forward Current of 1A. I'm not quite sure what that means.

Thanks very much for your help.

Click to expand...

That's not the case. The diode is not in the current path, but it is there to prevent high voltage spikes that can (and probably will) damage the FET.


Those spkes often occur when an inductive circuit - like the motor - has its current suddently turned off.

So the diode "woks" only for short moments, its average current is well bellow 1 A.


EDIT: Mikebits beat me to the response

This is still a valid question, for example you could use a 1N001 in a motor which draws 500A - the kickback will cause it to explode.

Thank you. Case closed: the diode isn't going to explode.

And, aside from the advice, I learned something.

Hero999 said:

This is still a valid question, for example you could use a 1N001 in a motor which draws 500A - the kickback will cause it to explode.

Click to expand...

Yes, but it will work happily with a 1.4 A motor.

The three parameters that you should consider so the diode survives:

>> Peak current (as you said, the diode accepts up to 50 A)
>> Average current (that is the ussual spec, in this case 1 A)
>> PIV or reverse voltage

Sorry meant you could not use a 1N4001 if the motor drew 500A but I think you got the general idea.