5V control I/O, to turn on off a 9V source

Hi All.

I want to use an Arduino I/O pin running a 5V, to turn on and off for a 9V source.
How can that be achieved the easiest?

I guess I cannot use a transistor, due to the difference in voltage.

Wired properly and selected appropriately, a transistor would work. Also, a relay, optoisolator, and MOSFETS would also work. Just remember that you can’t run a relay directly from the Arduino pins, it requires a driver circuit of some sort (either ULN2003/2803, transistor, or optoisolator); and there are single relay boards available for pennies on eBay, etc.

Yes you can use a transistor if it's rated. You can use a transistor to control another transistor. You can use a MOSFET style transistor or even an SSR.
Either way is fine just make sure they are rated for what ever amperage they will be passing (I go about 10% over) you may need a heat sink too.

Oh dear, one of those questions again - sort of "XY Problem". :astonished:

Look, don't waste people's time answering meaningless questions. Tell us what you want to do.

You could use a circuit similar to this which was intended to use a 3.3v arduino pin to switch on a 5v amplifier. AmpSw is the arduino pin and +5v (in your case +9v) is for the circuit to be switched.

HighSideSwitch.JPG

the_julle:
I want to use an Arduino I/O pin running a 5V, to turn on and off for a 9V source.
How can that be achieved the easiest?

I guess I cannot use a transistor, due to the difference in voltage.

That is routinely done using a transistor - assuming that 9V is DC. I do the same routinely for switching a 12V device with a 3.3V signal. Normally switching low side; high side is possible as well but needs a few more components.

Use a TRIAC if AC.

Did you even try a Google search for this question? Or is there something special about your situation that you forgot to mention?

More people's time wasted, and no reply in over 36 hours.

:roll_eyes:

I work on the concept - until and unless the OP engages in discussion, we have no idea what (s)he is up to, don't waste the breath!