We hacked an IKEA LED lamp to turn off automatically after twenty minutes. It’s our version of a light off timer lamp.
We have a bunch of JANSJÖ LED lights in our home.
They’re good quality, they have exactly the right mix of focus, intensity, and bendability. And they’re good value. Great stuff.
JANSJÖ LED light | IKEA.com
The only snag is that my family tends to fall asleep with the light on.
In the beginning I went around turning the lights off, but now we’ve found a solution that works much better: we’ve converted the lamps into turn-yourself-off-after-twenty-minutes lamps.
Materials for light off timer
If you want to make this lamp, then this is what you will need:
- An LED lamp with a section of low-voltage cord that you can cut; any voltage up to, say, 24 volts will do, but most are between 4 and 12 volts. Our IKEA lamp works perfectly for this. A lamp with a halogen bulb might not work well with this timer, since it draws much more current and doesn’t cut off cleanly; you’d need to do some tests. Do make sure that you’re working with low voltage – don’t try this on a cable that carries mains voltage!
- A logic-level MOSFET, with turn-on voltage below 4 volts; we used the IRF3708 (datasheet) in the TO-220AB package.
- A large electrolytic capacitor (we used 470 muF)
- A large resistor (we used 4.7 MOhm)
- A little piece of stripboard or veroboard (although one can also build the timer without)
- A push-button switch (normally off, push-for-on)
- A container to house the timer
- A voltmeter, or an LED, to to determine the polarity of the cable wires
- Some soldering skills
This Instructables post contains all the nitty-gritty, but here’s the executive summary.
The cord between the transformer (in the wall socket) and the lamp carries 4 volts, and one can insert a very small electrical circuit in that cord that acts as a timer.
For this you need a few electronic components and some soldering skills.
The end result is a lamp with an extra button in the cord: if you press the button, then the lamp turns on for about twenty minutes, and turns off at the end.
Now we can all sleep in peace, knowing all the lights are off.