James West

May include blinky lights. And cocktails.

Category: LEDs

The tea time klaxon

We’re lucky enough to have two teenage boys in the house. One of them lurks in the gloom of his bedroom listening to loud, raucous music and doing god knows what on his computer until he can be lured out by offers of food. But sometimes the music is so loud, or the headphones so firmly clamped that he doesn’t hear the call of “Tea time!!!” wafting up the stairs. I could go up to his room to get him, but this is the 21st century and there has to be a better way.

That better way is the Tea Time Klaxon.

Now I just need to send a tweet featuring the secret hashtag to trigger flashing lights and a buzzer to alert the eldest that tea is ready.

Actually, I’ve wanted to find an excuse to make something with one of these LED towers for ages, because they just look so cool, and recently they’ve been discounted at Pimoroni which gave me a good excuse to get one. The tower needs 12v DC so you can’t drive it directly from a Raspberry Pi. Instead I bought a power supply from Amazon – this one, I think and a Pimoroni Automation pHat to handle the switching.

I made a little plywood stand to hide the gubbins, which looks quite neat with a couple of coats of varnish. Inside you can see the Raspberry Pi Zero with Automation pHat hot glued into a corner.

Internals

I wasn’t sure how easy it would be to get the pHat and LED tower talking to each other, but Pimoroni’s python library for the pHat is excellent. It’s simple to read and is well documented so even a non-coder like me can get going with it very quickly. I borrowed a bit of code from their Blinkt! library to help look out for the hashtag on Twitter and was soon ready to go.

My final code is on GitHub, and you can see that it really is straightforward.

I enjoyed making this, it turned out to be much simpler than I first expected. It’s meant as a bit of fun because both our boys are lovely really, even though one does occasionally text us from his room rather than actually come and speak to us.

Quick make: Adding LEDs to a world map to show the status of stuff

In a recent sale my local branch of The Works was selling this cork world map. It was only a few quid – even less than the £7 sticker price and I thought it could be improved by adding some LEDs to it.

Today I finally got this sorted, starting out with a test build of the circuit, wiring two groups of LEDs in parallel (blue and yellow to match the buttons I’d got), with a 100 ohm resistor for each one.

I decided where to put the LEDs on the map, and drilled 3mm holes with my Dremel for them. I also marked out where the buttons needed to go and used a craft knife to cut through the layers of cork, corrugated paper and card that make up the sandwich of the board. The LEDs were hot-glued into place after being pushed through the map, Because the board was quite thick they ended up being just about flush with the surface which gives quite a nice effect when they light up.

I also fastened a 3 x AAA battery box onto the back and stuck the power rails from a breadboard nearby to help hook up the LEDs.

Next I soldered a resistor to the cathode of each LED and wired up the buttons and battery pack to the breadboard. Then I connected the LEDs to the power and used electrical tape to cover up the exposed LED legs to prevent an short circuits.

I’m happy with how this came out. The location of the LEDs in this case isn’t important, they can be used to indicate whatever you imagine: the location of Dalek invaders and UNIT forces for instance. You could put them on specific continents or oceans to help with geography homework or show where particular food, animals, or resources come from.

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