Go Down

Topic: Digital power switch? (Read 1 time) previous topic - next topic

I'm really new to Arduino, and currently working with a project in which I'm looking for a way to digitally control power supply for an old  television (just on/off).

While the TV obviously demands more power than 5 volts. I figured an easy solution would be something like mounting a "digital" On/Off switch on the power cord that goes into the wall, which i can trigger (on/off) with a digital out pin from Arduino.

Is there such a device? Or am I trying to do this in a stupid way? :)

Appreciate any help i can get.


a simple way is to use a relay to control the tv on and off. just look for any relay shield would be suffice.


There are digitally controlled power switching solutions like this that will keep you safely away from the high voltage, if you are careful: https://www.adafruit.com/products/268

Anything above 5 volts can kill your Arduino, and 110VAC can definitely ruin your day, so do be careful and read up on electrical safety before embarking on any high-voltage work.



The relay idea will of course work -- it's what's in the product I pointed to -- but I wouldn't recommend running live 110volt AC power on any board to a newbie to electronics.  The cost of small mistakes is too high.  Too much possibility of getting hurt.



sorry billroy if my post offended you. At the time of me posting my post i didnt saw your post. and yes is true, i should have not gave any recommendation that could endanger someone.


No offense taken, sir.  Your advice was valid but a little incomplete on the safety side ;)

Best regards,


Thank you very much for your help. As you said, I am definitely a beginner at this so i really should really read-up on the possible hazards before doing this.

The powerswitch tail looks easy to use and is a very good tip. (while i probably need a 230v version in that case, I'm living in Europe and we have a 230v electric system.)

After i posted the question, a had another look on the TV (Portable Sony Mega Watchman.) It also has the choice of a 12v DC power in (and i have a 230v->12v Transformer.)

I also found that I own this relay (comes with the sparkfun inventors kit):

Does the information provided above mean that it's a more simple thing to do, and would the relay be something i could use for this project? And if so, how would i plug it in? Couldn't find any information on the site.

Again, thanks for the help.


I work at Omron that manufacture relay  for almost 2 years. What i can say about a seal relay is that it is a great relay that you actually could use submerge under liquid. if you only have the relay then you need a couple more thing to make it work,
1)a Transistor/Optocoupler would be great
2) a signal Diode,1n4001
3 A power supply that can supply enough volt to activate the relay coil.
wires / board
and last but not least a box preferably a plastic box big enough to contain it all


That relay is rated for 5 Amps, which at 12 Volts means it can switch a 60 Watt load (12 x 5) with zero margin.  I'm guessing your TV needs more than 60 Watts, but you can check on the nameplate.  It may even say how much current it needs.  Fortune favors those who operate with safety margins.

So probably not, but a similar relay with a higher current rating would be a good candidate.

Connecting a relay to a digital output pin requires a transistor, a base resistor for the transistor, and a flyback diode.  If you search the forum there are plenty of examples.



dear Billroy i would like to point out that, actually your calculation have some flaw in it. According to the datasheet, It is a 12Vdc relay and it need 37.5mA of current run thru the coil to activate the relay thus closing the contact. ON the Contact part, if the relay is use to power a resistive load, if its an AC circuit ,it can handle 5Amp at 250Vac Max or 5Amp at 30VDC. The total Max Power is 1250 watt for Ac and 150Watt for DC.


The contacts are rated for 5 Amps.  Exceeding that means you've got no thermal safety margin.  At 12 volts, 5 Amps is 60 watts.

You could squeeze more power through the contacts at a higher voltage, but my understanding is that the load wants 12 volts in this case.

Fortune favors those who design circuits with wide safety margins.



Again sorry billray, I miss read the post above, and yeah the contact is rated at 5 Amp. urm maybe what you need is a power relay maybe the kind of relay that i use to make
if you could find a G2R-1-S relay from omron, well that would be great. or the more common would be the MY-2 model.


If I were doing this, I'd consider getting these http://www.maplin.co.uk/remote-controlled-mains-sockets-3-pack-531561 IR-controlled sockets and programming the Arduino to generate the correct IR code for them. But to do that, you need to be able to read IR codes, which requires the right equipment e.g. an oscilloscope and a photodiode.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131