Modifying a Xiaomi Zigbee Button

Posted on 2019-02-05 in makes

In late 2017, i was fiddling around trying to teach myself fusion 360, and accidentally found myself designing a giant red button. I didn't really have a use for it at the time, so i added a microswitch, printed it out, and had a random giant button sat around in my office, mostly getting in the way.

The Button

Fast forward a bit, and i've implemented a home automation system with a zigbee network, and a £5 Xiaomi Aqara Zigbee button. This button is around 5cm x 5cm, battery powered, and as far as I can tell lasts for infinity time from a single coin cell. I can't help but think though... what if it was giant instead?


Step one was of course to open up my nice new button. Quick attack of the spudger had the case popped open and ready for a bit of probing. Now, if i was designing this board, i'd probably duplicate the button out to a test pad or pin header somewhere. Luckily the engineers at xiaomi appear to agree with me, and the header in the top right is connected directly across the input switch, score!

Wires to the front of the board Wires to the back of the board

I soldered a couple of wires to the board, and added some hotglue to provide a minimum of strain relief. As an aside, look at all those lovely labelled test points on the back of the board, this could make a fairly nice development board for the NXP zigbee microcontroller.

Wires to the microswitch

I wired in a microswitch to the other end of my cables, and pressing the microswitch triggers the button, yay!


A small amount of poking with a scalpel let me remove enough plastic from the corner of the case to feed the wire through and assemble the Aqara button.

Fitted into button

Assemble into the button, and a little bit of hacking to make an automation in homeassistant, and we have a light switch for the 3d printer light!

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Project - Lil' Buggers

Posted on 2014-05-12 in makes

Lil Buggers

We like to do occasional workshops at the Hackspace, so when we were asked to make something 'bug themed' for a workshop, we jumped on it.   The first thought we had was to make up some bug-shaped PCBs with a circuit to flash LEDs, and run a soldering workshop.  When we found out the workshop was a week away, we panicked a little, as that's not really enough time to get PCBs manufactured at a sensible price.

We decided instead to make little laser cut bugs with LED eyes, as they can be made with easily available materials, and infinitely customised.

Step one was to choose a material.  Our first experiments were with acrylic.  I whipped up some designs for 'joints', which would friction fit onto the side or top of a 'body'.  I attached these to a curved path in inkscape for the legs, and bug #0 was born!

Bug 0

Bug #0 had a couple of issues, mainly due to the material choice.  Acrylic thicknesses can be a bit variable, the tolerance can be as wide as ±10%, and it is fairly brittle.  the combination of these two issues caused at least one broken leg (hence #0 having 5 legs!).

We decided to have a go at laser MDF instead.  Laser MDF is basically MDF made with a glue that is less harmful to people and laser cutters than regular MDF.  It has the advantage of being very dimensionally accurate (our 3.2mm MDF was measured at 3.21mm), and having a bit of bend before it breaks.

Bug 1

Bug #1 was born.  It assembled a lot easier than #0, and has cool looking scorched edges.   At this point I started designing some add-on parts to allow attendees to customise their bugs, including wings, tails, hairy legs, and mandibles.

The only issue with #1 was losing the wide range of colours available from acrylic.  However, I had a flash of inspiration, and gave a sheet of laser MDF a light coat of red spraypaint.   This dries fast, and gives an awesome splash of colour.

Bug 2   Bug #2 is alive!  This time sporting a lovely pair of wings and some antennae. #2 was done with just one side of the wood painted, which gives a cool effect. depending on what side of the bug you're looking at.

Then things got a bit silly...


We now have a swarm of these delightful Lil' Buggers invading the hackspace.  With a magnet and a dab of hotglue they'll stick to anything metallic, and their LED eyes last for a couple of days on a coin cell.

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45 Minute Project - £4.10 XBMC Remote Receiver

Posted on 2014-03-01 in makes

I'm a big fan of XBMC, and have an Ouya running XBMC set up in my lounge, streaming from my NAS. I normally use XBMC remote on my phone for controlling it, but this gets annoying when the phone is on charge, or I'm using it for something else.

I noticed that the majority of my TV remote is completely unused when the TV is in HDMI mode, and had a bit of a lightbulb moment!

Remote Almost none of these buttons are used!

I already had an Arduino Pro Micro (£3) lying about i'd bought for testing out as an upgrade path for the minimus based projects i've been playing with.  It is leonardo compatible, small, cheap and pretty easily available.  I added an IR Receiver (£1.10) to the weekly Hackspace Farnell order to complete the parts list.

The pinout of the IR receiver makes it very easy to connect to the pro micro, using the RAW (VUSB), GND, and A3 pins.  I just bent the OUT pin (pin 1) on the receiver to the left a bit as follows:

Front Back   The body of the receiver fits perfectly behind the USB plug, flat against the voltage regulator.  I used the IRremote arduino library to grab data from the remote using the IRrecvDemo sketch and mushed some buttons:


My remote uses 0xFFFFFFFF as a 'key repeat' code, about every 200ms when the button is held down. I found that in practice I had to ignore the first of these, as it was repeating way too fast and doing double presses.

I tweaked the IRrecvDemo sample code, added in a bit of keyboard and came up with some working code:

#include IRrecv
int RECV_PIN = A3;

IRrecv irrecv(RECV_PIN);
decode_results results;

int key;
int count;

void setup()
  irrecv.enableIRIn(); // Start the receiver

void loop() {
  if (irrecv.decode(&results)) {
    switch (results.value)
      case 0x8B452AD: // up
        key = KEY_UP_ARROW;
        count = 0;
      case 0x8B410EF: // right
        key = KEY_RIGHT_ARROW;
        count = 0;
      case 0x8B4D22D: // down
        key = KEY_DOWN_ARROW;
        count = 0;
      case 0x8B4D02F: // left
        key = KEY_LEFT_ARROW;
        count = 0;
      case 0x8B4926D: // enter
        key = KEY_RETURN;
        count = 0;
      case 0x8B412ED: // red
        key = KEY_BACKSPACE;
        count = 0;
      case 0x8B4B24D: // green
        key = ' ';
        count = 0;
      case 0x8B44AB5: // yellow
        key = KEY_ESC;
        count = 0;
      case 0x8B450AF: // blue
        key = 's';
        count = 0;
      case 0xFFFFFFFF:
        key = -1;

    if ((key != -1) && (count!=1)) // if count = 1, it is the first key repeat, so ignore it.

    irrecv.resume(); // Receive the next value

Total cost £4.10, total time 45 minutes. Sorted!


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3D printing - Bandsaw Fence

Posted on 2013-03-21 in makes

I spent some time earlier in the week getting the bandsaw at Hackspace Manchester working, so now its cutting again!  The main problem with the bandsaw is cutting straight, as it was an ebay purchase it diddnt come with a fence, so there was nothing to run the cut material against.  This model of bandsaw hasnt been made in around 30 years, so trying to buy a new one will be impossible, and ebay is too much hard work.

Though we do have a 3d printer... and a workshop.  Idea!

Step one was to have a look at the bandsaw.  It has a channel running along the front , so I took some measurements to see what I was working with.

channel paper

So, i had the measurements, it was time to take to my CAD software and design something to fit in the channel.  My choice for this is OpenSCAD.  I used it to first create the shape of the channel, then to carve this shape out of a block.

openscad1 openscad2

I extruded this to a few mm wide, then printed it to test.  There was a bit of tweaking needed to get it to fit exactly, so i ended up doing 4 iterations with the sizes tweaked slightly.


testprint test

Once i had one that fitted, i printed it out extruded to 20mm to check it would fit and slide correctly.


It did, so i moved onto designing the actual fence.  Step one was to cut some aluminium extrusion to size, and measure it.  A month or so ago I had managed to womble a nice straight piece of 16mm x 16mm  3.2mm thick L channel, which was pretty much the perfect size.  I cut this to size, and modelled it in openscad.


The actual cad modelling took a couple of hours of tweaking, but i the above picture shows the basic steps.

First off i extruded my clamp to 50mm wide, and added a wedge to the side of it.  50mm gives enough width for it to sit in the runner, and counteract twisting force from the back of the fence being pushed on.  The wedge is to give support to the top part of the L channel.

Second, I added two captive nuts and holes for M5 bolts.  Mainly because we have a massive bag of M5 hex-head bolts that are perfect for printed thumbscrews. Theoretically i could have threaded into the ABS directly, but i felt this wouldnt last, so embedding a nut seemed like the best option.

Third, i carved out the hole for the L channel.  This leaves a bit of an odd shaped unsupported piece, which may be weak. Because this piece will be in the channel, i decided to leave it, as it'll make measuring up on the built-in ruler more accurate.

Lastly, i added some pilot holes for attaching the aluminium to the 3d printed part.  i decided to use 3mm x 12mm self tapping screws for this, because i had them on hand, and they can be countersunk fairly easily.


I test-assembled the whole thing in the vice, it fitted nicely in the channel, so it was ready for connecting together.  I marked, center punched, drilled and countersunk the holes for the 3 screws that hold the whole thing together.  Add some screws and we're sorted!


Of course, i had to do a test cut at this point, so some of the scrap acrylic pile was chopped into little strips.


Woohoo, it worked!  All it needed to be complete is some knobs.  So i headed over to thingiverse to find a knob that'll fit nicely over an m5 nut... and found nothing useful.  No worries, i just OpenSCADdded one up.



So there it is, a useful thing i've made on the 3d printer that wasnt a part for a 3d printer!

Source files (stl, openscad) are available on My GitHub 

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The PANIC Button

Posted on 2012-02-19 in makes

Ok, bit of explanation first.  We have an iMac set up as a 'democratic jukebox' at Hackspace Manchester.  The idea being that anyone can put music on it, and it plays the entire library on shuffle during our hack sessions for a bit of background music.

The problem is, of course, some people have an... odd taste in music, so sometimes the jukebox ends up flipping between Aqua and Cannibal Corpse for ten minutes, and the horror of this was just too much!

Enter the PANIC button.


The button uses a minimus board. The minimus is a carrier for the AT90USB162, an AVR microcontroller with onboard USB hardware, which means it can be programmed to show up as any USB device.  Before getting the button I modified one of the pieces of LUFA demo software, a media keyboard, and stripped it down to just read the one button on the minimus.  When the button is pressed, it sends the keycode for next track. 

The button's housing is a joke button that played an alarm and flashed when pressed, I ripped its guts out to get to the switch.  After finding the switch contacts on the original board, i soldered on two wires to connecto to the AVR.


Next,  I stripped off the USB connector  from the minimus, and added a 1m USB lead directly to the pads, to make it fit in the old speaker housing section of the button.  I connected the leads from the button to PD7 and GND on the minimus, the same as the onboard button.  This has the handy side effect that if the button is pressed while being plugged in, it boots into DFU mode, allowing me to upgrade the firmware easily.


I cut a slot in the casing for the wire to escape, and added a couple of cable ties for strain relief.

Press Button, Song Skips, Panic averted!


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