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

Using Arduino General Electronics
#1

Hi,

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?

Thanks

#2

Lars1408:
as you can see in the picture

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

#3

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

#4

whooops :o

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#5

Here’s OP’s pix inline:

07d5689ae47f2a5fee5afb50a103d4a841726b7f.jpg

c38a2324c8c03fb373f319592d933837c7ad3f79.jpg

#6

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.

#7

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

#8

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

#9

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

lamp mosfet.gif

#10

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).

#11

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

#12