How to apply a 4vdc 0.75A 3W lamp to an Arduino Uno


I have a lamp that works with an adaptor 230v -> 4V 3W 0.75A
You can just unplug the adapter as you can see in the picture(i'm assuming that the biggest pin is the positive??). I would like to connect it to my arduino so I can control it usinng wifi or IRremote.... Etc. Does anyone know how I can connect 0.75Amps to an arduino uno?


as you can see in the picture

Or more likely, can't see, since it's not there.

If the lamp uses dc you can use a n channel mosfet with an externel power source but if it uses ac i can not help you since i am not an expert in electronics

whooops :o

Here’s OP’s pix inline:



You need a meter to check which is the +ve.

Then cut the -ve and as NewStudent says, bung an n-mosfet in there with the mosfet source pin to the -ve going back to the adapter and the mosfet drain pin going to the lamp. Then the gate of the mosfet goes to an Arduino pin for control.

EDIT... NB: so we're both saying, the power supply still stays in play. You can't power 750mA from the Arduino itself, but you can control the external power easily.

ok thanks both for the quick response.. :slight_smile:

I've drawn a crappy pic of the circuit but atm it's too big to upload. Trying to make smaller...

Here’s crap pic of how I think it would connect. Details of mosfet and resistors subject to discussion.

lamp mosfet.gif

The labelling is a bit confused, it says primary and secondary, yet the output voltage has a DC symbol...

I presume its a SMPS with DC output, and its got the double-insulated symbol so it should be fully
isolated (and its a not a chinese cheapy, so it probably is fully isolated).

In the picture manor_royal posted the resistor between gate and source can be 10K an the resisyor between gate and the digital pin can be 100 ohms