{"id":17945,"date":"2017-12-15T12:09:07","date_gmt":"2017-12-15T11:09:07","guid":{"rendered":"http:\/\/www.recantha.co.uk\/blog\/?p=17945"},"modified":"2017-12-15T12:19:23","modified_gmt":"2017-12-15T11:19:23","slug":"anavi-light-phat-for-the-raspberry-pi-a-review","status":"publish","type":"post","link":"https:\/\/www.recantha.co.uk\/blog\/?p=17945","title":{"rendered":"Anavi Light pHAT for the Raspberry Pi – a review"},"content":{"rendered":"

\"\"<\/a><\/p>\n

Review by Tim Richardson<\/a><\/em><\/p>\n

What is it?<\/span><\/h2>\n

The Anavi Light pHAT<\/a> is a board that sits on top of your Raspberry Pi and controls 12v RGB light strips – not the expensive Neopixels or WS2811\u2019s, but the cheap RGB strips that you can get for a few pounds for 5m from AliExpress or eBay.<\/span><\/p>\n

Why use one?<\/span><\/h2>\n

These LED strips (often labeled \u20185050\u2019) are powered by a 12v power supply and the colour is changed by supplying a PWM signal. \u00a0This is often done by a microcontroller device with an IR controller, but the controller usually gives a very limited choice of colours – perhaps just 16, and only one strip can be controlled at a time. \u00a0But what if you want other colours? Or want to control more than one strip at the same time? For that, you need a little more intelligence. \u00a0In comes the Anavi Light pHAT<\/a>.<\/span><\/p>\n

How to use one?<\/span><\/h2>\n

As mentioned, the pHAT sits on top of any 40 pin Pi, like the Pi Zero W or Raspberry Pi 3. \u00a0You attach your LED strip to the screw terminals (max 5A – enough to control 5m or more) and a 12V power supply.<\/span><\/p>\n

Unfortunately you have to power the Pi separately; there is simply no space on the board for a voltage regulator to back-power your Pi. \u00a0Instead there are three i2c ports, a PIR port and UART pins if you want to access the Pi directly. \u00a0I spoke to the developer, Leon, about this, and agree with him that adding the ports gives the pHAT much more versatility than having the regulator. \u00a0But, if there is enough interest, he may make a HAT version that has the regulator!<\/span><\/p>\n

Changing the colour of the LEDs is as simple as supplying PWM signals to pins 9, 10 and 11. \u00a0Examples given use the PiGPIOd library – which runs a daemon to control the GPIO ports – you tell the pins what to do once, and they just get on with it. \u00a0Even on a Pi Zero this takes very little CPU (about 6 or 7%) leaving the rest for you to use with your program. \u00a0During my testing, I used the GPIOZero library\u2019s RGBLED class to control the whole strip. It worked perfectly first time.<\/span><\/p>\n

The i2c ports are intended to be used for sensors. \u00a0As part of the Crowdfunding campaign<\/a>, Leon is optionally supplying three different i2c sensors and one PIR sensor. \u00a0The i2c sensors are for light, temperature\/humidity and RGB colour and gesture detection. \u00a0As well as the sensors, he will be creating the code to control the LED strip in reaction to sensor changes. \u00a0You could, for example, make the lights turn on when there is movement, or change brightness depending on how dark it is, or when presented with a colour object, change the strip to that colour. \u00a0Or even when it\u2019s hot, turn the LEDs blue to cool you down, or red if it\u2019s cold to make you feel warmer (it\u2019s a psychological thing!). I suspect some of Leon\u2019s sensors could use GPIOZero code too, which will make it very simple to control the LEDs.<\/span><\/p>\n

Leon also plans to supply code\/instructions which will allow you to integrate your LED strip into your Home Assistant<\/a><\/span>\u00a0setup.<\/span><\/p>\n

All the hardware designs and software are, or will be, open source!\u00a0 This is very generous and could lead to derivatives.<\/span><\/p>\n

How to get one<\/span><\/h2>\n

Leon is currently using Crowd Supply to kickstart the project<\/a> <\/span>but has put a very low goal – meaning it\u2019s definitely going to get funded and built. \u00a0The price is a little higher than I had hoped when I first heard about it, at $25, but when compared to a solution I have already built for about \u00a310, it\u2019s so much neater and better!<\/span><\/p>\n

When compared to buying even a 1m NeoPixel light strip, it turns out to be much cheaper. \u00a0Okay, each individual LED on the NeoPixel strip can be set to a different colour, but when you are using it for lighting are you really going to do that? \u00a0You also need to add a controller on top of that.<\/span><\/p>\n

Recommended?<\/span><\/h2>\n

This board is something I was looking for quite a few months ago, but couldn\u2019t find. \u00a0I did make my own version – not as a pHAT, but as a string of cobbled-together parts. It wasn\u2019t that neat, but it was cheap and very ugly! \u00a0Personally, I\u2019m going to buy these for my project and abandon what I have. \u00a0If only I could power the lot from one power supply…<\/span><\/p>\n

Back the project on Crowd Supply<\/a>.
\n