[TriEmbed] Transistor as switch

Carl Nobile carl.nobile at gmail.com
Mon Jun 15 16:58:49 CDT 2015


Brian,

The max collector current on the 2N3904 is 200 ma, so to be safe you would
need to keep the current real low. If you motors can peak higher than 200
ma you may eventually burn out the transistor, so you will also need to put
a 0.1 uf cap from each lead of the motor to ground (assuming that neither
of the leads are ground).

This is not the best solution for a motor, because motors are inductive and
will cause reverse pulses and do a lot of spiking. In a pinch it may work
however, but don't design this into a permanent project. If you hook this
up to a microcontroller or your RPi think about having extra cash around to
buy a new one when the motor sends a big spike back through the circuit.

In other words without seeing the motor and it's specs. it's hard to guess
what would happen.

Carl



On Mon, Jun 15, 2015 at 5:37 PM, Grawburg via TriEmbed <
triembed at triembed.org> wrote:

> Shouldn't a 2N3904 transistor be able to switch a 5VDC motor?
> My circuit is correct since I tested it first with an LED, then replaced
> the LED with a cheap little DC motor. (I did use a diode to protect the
> circuit).  I'm using the Pi for the necessary voltage on the transistor
> base.  Yes, I did check to see if the motor worked with 5V.
>
>
> Brian Grawburg
>
>
>
>
>
> _______________________________________________
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Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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