After creating bespoke lighting for three artworks, I have lots of experience of using 10 Watt LEDs and Arduinos, so I decided to create something for myself, something that I can use long after I’ve moved on to new types of project.
I decided to create a bedroom lamp. I had two things in mind – I wanted to incorporate a remote controlled dimmer, and a dawn simulator (where the light slowly fades in as a gentle wake-up).
I began by imagining the lamp as an uplighter, with the lamp unit held above head height and the light bouncing off the ceiling, to avoid having one very bright lamp. The lamp would need following basic parts:
1) A heatsink to attach the LEDs to
2) Electronics – LEDs, power supply and controls
3) A clock / timer to trigger the simulated dawn
4) An exclosure, to make it look like a lamp and something long to hold it at head height
5) A power supply
LEDs get hot. About 70% of the electrical energy used ends up as heat. I had been thinking of using four LEDs (a red and a yellow to mimic sunrise, and two cool white). This would, if they were all on full, create 40 x 0.7 Watts of heat, or 28 Watts. That’s not so much, but will need a heatsink. An initial estimate is that it will need to be about the size of a small stack of coasters.
So far, I have controlled all the projects with Arduinos. I previously bought five Arduino nanos for £2.39 each, so it seemed sensible to use one of those. Similarly with the LEDs. I bought 5 cool white LEDs for the Flash in the Bearing Witness project, so I still have two left.
The main purpose of this lamp is as a dawn simulator. So, in place of an alarm the light will very slowly fade in, like a sunrise. To add to the effect, rather than have only while LEDs, there’s also a red and a yellow LED. This means the colour can approximate a sunrise in colour as well as brightness. So I sent off for a red and a yellow (10 Watt LEDs are about £1 each).
3) Clock / Timer
I bought a little alarm clock. Surprisingly, for £10 it works really well. It’s battery operated, so proof against power cuts, and it sets the time using a built-in radio receiver that picks up time signals from Rugby in the UK. The alarm is a small sounder, so I shall unsolder that and add a socket for connecting to my new lamp. When the alarm is triggered it will begin the dawn simulation.
4) An exclosure, to make it look like a lamp
Basically, I had in mind a simple piece of tubing. Maybe something metal and shiny.
I found a piece of plastic tubing at Screwfix , designed as a through-wall air guide for an extractor fan, for £2.63. It’s 12cm diameter and 35cm long – just the right size!
I originally planned to spray-paint it a nice cream colour. However, on getting it home I realised that it’s not designed for show. The ends are roughly cut and it slightly squashed, i.e. not perfectly round. So, Plan B. I looked around for a nice piece of cloth to cover it with.
To hold it at head-height I wanted to use some long thin branches from a tall bush/tree (I’m not sure what it is!) that I cut down last year. It seemed a simple task to artistically arrange three into a tripod on which to perch a lamp. Actually, it was not a simple task at all. In the end I had a much better idea. I decided to simply stand the lamp on the chest of drawers in the bedroom. By placing the LEDs some 10 cm down inside the tubing it’s not possible to look directly at the LEDs by accident – one would have to “peer over the top”.
5) Power supply
I already had a spare 12 Volt 5 Amp power brick from the Bearing Witness project, so I wanted to use that. Using a resistor in series with each LED to limit the current was a simple and effective approach that had worked well, with the Arduino checking the power supply voltage and shutting the lamp off if it went too high – more than a few tenths of a volt – and additional logic to shut the power off if the heatsink temperature rose too high). So I planned to do the same this time.
So, let’s get started! The first step is to choose a suitable heatsink and make some form of frame to hold together the heatsink, circuit board and case…