Retrofit Remote Light Switch V1 – A Failure

The Plan

At some point we have all wished to just click our fingers and make our lights turn off, without having to get up and flick the switch.

Whilst you can get expensive light switches which do this, it struck me that with some 3D printing and cheap electronics, I could make my own remote control system which I could retrofit onto any standard light switch.

I also think it’s an interesting design challenge which can be approached in many ways, giving plenty of options for inventing and experimenting.

The Design (baby CAD it up, CAD it up)

I started the design in Fusion 360 – a CAD programme which I don’t have much experience with, but in the little time I’ve been using it I have fallen in love. It’s intuitive to use and allows you to build up a complicated assembly, and then split it into much simpler components for 3D printing.

The design itself is pretty simple, it uses two servos – one positioned at either end of the light switch to turn it on and off. You can see one of the servos (in blue/white) in the following picture, held in place by an orange bracket, hovering tantalisingly over the light switch…

The Assembly

I don’t have my own 3D printer and so I ordered the prints from an online service. I was excited and a bit impatient but luckily the prints arrived in two days – not bad for £9.50 all in!

To my delight, the prints fitted perfectly and pieced together just as I had intended when designing in Fusion 360.

First, I attached the base plate onto the light switch and then added the servos into their mounting brackets. I also fitted little blue extenders which clipped onto the white servo arms to ensure they could reach the light switch.

Next up is the circuitry – I created two little holders which screw into the base plate and clamp the circuit board in place.

The circuit board is bare in the following picture, but I intended to solder the electronic components on once I had made sure it worked…

I also had a similar part for the battery which screwed onto the side of the baseplate and made use of the existing holes in the battery holder.

Putting it all together

Here it is fully assembled in all of its robotic glory! The servos and circuit board fit on top of the light switch, but the battery holder had to hang off the side. There wasn’t really room for everything within the footprint of the light switch using this design, but maybe with some improvements I will be able to make it all fit.

Up to this point everything was going to plan, but unfortunately the success ended fairly quickly when I got to testing.

Testing

I assembled the circuit using an Arduino to control the servos. Everything was powered through a 9V battery, connected to a 5V voltage regulator. I went with this setup to make sure that it could handle at least 600 mA of current – the maximum you might expect from a single servo.

With hope and anticipation, I connected everything and ran my first test. The result was a bit disappointing, and revealed a design flaw which I had completely forgotten to account for.

As you can see, the servos are not very rigid and bend as they push down on the light switch, creating an unnatural curving motion as the arm slides down the slope of the light switch.

Whilst the servo did successfully flick the switch, it was not an elegant or robust design. Furthermore, the light switch I was using to test was very easy to flick and did not have a large slope on the switch.

For more resistant or sloping light switches, this definitely wouldn’t have worked.

Another minor issue is that the little blue arm extenders were pushed at a weird angle, causing them to dramatically ping off, as you can see in this video:

Conclusions

Despite the poor outcome of this project, I really enjoyed it as it taught me something I didn’t even consider at the design phase. I also think there were some successful bits, like how all the 3D prints fitted together so well.

In CAD, everything looks so solid and you only imagine it working as you intended. However, in the messy world we live in, things can be flimsy and bend or act in ways we didn’t anticipate. This is certainly a valuable lesson for me to take forward into future projects!

The next attempt at a remote light switch will take the failures of this first version and try to overcome them – it will avoid the awkward bending and will ensure that any extenders fitted to the arms are firmly held in place.

Thanks for reading through – if you found this interesting, feel free to leave a comment or hit me up on Twitter.

Happy hacking,

Robin

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