I’ve wanted to play with individually addressable LED’s for ages and I’ve finally got around to buying some so it’s time to go it. For this project I’ve decided to build a 16×16 array of LED strips based around the common WS2812B chip.
Since I’ll have a 16×16 array of LED’s the total count will be 256. Each WS2812B chip can consume up to 60mA at 5V so the total current draw running full white would be 60 * 256 = 15360mA or 15.3A @ 5V – that’s a lot of amps! Power wise that’s 15.3 * 5 = 76.8W. Fortunately you can fairly easily pick up 100W 5V power supplies that will work for this project. You don’t want to be running your power supply flat out all the time, a 75% loading is about a much as it should do full time. In reality this display will pull much less than 75W, I’ve powered up a single 16 LED strip and when set to all white it’s almost blindingly bright.
As I’m new to electronics I am more than a little concerned that what I build might not be safe. While researching this project I came across this Hackaday video about fusing each LED strip. To my mind that video makes a lot of sense, the resistance of the LED strip is sufficient that it could get into a position where it was drawing a significant number of amps but not triggering the protection in the power supply (assuming a cheap and nasty power supply even has protection).
Originally I was planning on powering each strip of 16 LED’s separately but I’ve come to realise that’s making work for myself and so instead I’m going to batch them up into runs of four giving 64 LED’s per run. That gives a current draw of 3840mA / run. A cheap way to get low voltage fuses is by using blade fuses for cars. You can easily and cheaply get 5A blade fuses and a carrier.
I thought this was going to be a fairly cheap project but it’s turned out to be quite expensive for what will probably be a little used lamp in the end. Here’s a list of the items I’ve bought.
- Aluminium plate, 300x300x3mm, eBay, £9.99
- Mini-blade fuses, 40 pack, 5A, eBay, £2.99
- Capacitors, 1000uF 10V, eBay, £3.19
- Inline fuse holders, 5 pack, eBay, £3.75
- Wire, 4 core, 22awg, 5m, eBay, £3.69
- LED Strip, WS2812b 5050, 60LED/m, 5m, eBay, £18.60
- Power Supply, 5V 20A, Amazon, £17.99
- Fuses, fast-blow glass fuses (for the kettle socket), variety pack, Amazon, £12.99
- IEC (kettle) Socket, 3 Pack, with fuse holder and switch, Amazon, £9.99
Not yet included is the Raspberry Pi or Arduino I’ll be using to control the light or the box this will all be included in. The box will likely have a zero cost for me as I have materials on-hand.
I initially planned to run this project off an Arduino Uno as they are cheap but by the point I’d bought all the other pieces I figured I might as well go all in an buy a Raspberry Pi as well.
These are the costs of what I initially bought. It’s really not necessary to run this project off a Raspberry Pi 4 Model B but that was what I wanted to start off on. I’ll go back and update the main costs once I’ve decided on what I’ll be using. I suspect I’ll use a Raspberry Pi Zero or something like that. It’s got more grunt than an Arduino and is a bit more friendly for the kids to interact with.
- Raspberry Pi 4 Model B, The PiHut, £54.00
- Aluminium Armour, heat sink and case, The PiHut, £12.00
- Micro HDMI to HDMI cable, The PiHut, £3.80
- USB-C power cable with switch, The PiHut, £3.00
- USB3.0 Extension Cable, Amazon, £5.38
- SD Card Reader, Amazon, £12.99
- Logitech K380 Keyboard, Amazon, £32.99
So that’s what I’ll be putting together into a lap, time to get building and coding. As with many of my projects I got started on this one and then left it for an age (about 3 years) so now I have the unenviable task of trying to figure out what I was doing. At the time of writing the lamp is actually built and I’ve powered it up and even had basic patterns displayed. The problem is that was years ago and I’ve forgotten exactly how far I got with the project so now I’ll have to redo a load of work. See you in part 2.