Don't buy the wrong Heltec device

heltec wireless stick.PNG

It turns out that I’m perfectly capable of making the same mistake twice. In fact, I seem to insist on doing this.

A couple of years I bought three Heltec devices that were configured for the American market. They worked fine, but only on the 433 MHz network that they use for Lora in the ‘states. For the UK and Europe you need 868 Mhz ones.

A while back Adam told me about a new Heltec Wireless Stick that looked interesting. I was intrigued, so I bought one. The product listing implied that it worked on all of the wavebands.

Mine doesn’t. It has 433 written on the box. It’s a nice enough device, but much less useful than I was planning.

Moral of story: check the transmit frequency of any LoRa device that you might think of buying.

Server Discussions at c4di


We had a quiet, but useful, hardware meetup today at c4di. Although most of the talk was of servers and software.

We’re in the process of migrating our services onto a shiny new Azure platform (if virtual machines can ever be regarded as shiny). As of today we’ve got the bulk of the work done. This means that you can go to our map and see something useful. We made some changes to the configuration live at the meeting which was great fun. I also insisted that we turn off the server and then turn it back on again, so that we could make sure that there are no manually started services that we need that would cause things to break if we ever had a reset. I’m pleased to be able to report that the server passed with flying colours.

Next we have to move our web sites and a couple of other services and then we’ll back in business. Huge thanks to everyone, particularly Starbeamrainbowlabs and Brian, for making the move.

Starbeamrainbowlabs has written some neat blog posts on the migration process that you can read here.

Any Solar Power experts out there?

solar power.PNG

I went to a meeting yesterday with some folks who are interested installing some of our air quality sensors. However, we have a major problem with this because at the moment our devices are all mains powered. This is mainly because the particle sensor is quite a power hungry beast. It needs to be fed with around 120 milliamps. This is not a huge amount, but it is enough to make long term battery powered deployment a bit of a no-no.

It looks like there are some devices out there, I’ve ordered some of the one above, based on the MCP73871 chip. If anyone has ever used this kind of device and got a happy ending I’d love to hear from you.

Cheap project boxes

What you can get for seven pounds

What you can get for seven pounds

Making boxes to put projects in is hard work. You can 3D print them but that takes ages. You can laser cut them (but you need a laser cutter). And making things waterproof is really hard too.

Turns out that terminal boxes make great project boxes. They arrive waterproof and the holes in their sides have nifty little rubber plugs in them which you can cut to fit whatever you really want connect to. It turns out that the buttons that I bought last week can be made to fit in the sides with just a modicum of surgery. We’ve also used these holes to provide inlets for air quality sensors.

If you’re lucky you might find that you can shine neopixels through the rubber plugs to get a nice lighting effect - like I do for the two button game. I don’t think this will work with the boxes above though, their plugs seem quite opaque.

Terminal boxes are available in lots of sizes and really good prices. I got the ones above from Screwfix.

Cables for a pound each


If you’re looking for some cheap cables I can recommend you wander down to your local pound shop. I’ve been using their cheap usb cables for a while and they work a treat. They are especially useful if you want to connect up a Wemos or Heltec device to a power supply. They have a good length, 1.5 m, the connectors are sturdily attached, they are packed in a nifty little bag and they only cost one pound each.


I’ve also been using their one pound HDMI cables and they seem to work fine. It seems that electricity doesn’t mind the price of the wires that it travels down…..

Bringing an Alien back from the grave


Me and my Alienware laptop go back a long way. We need some spare laptops for a course that I’m helping with, and I was wondering how hard it would be to get an 8 year old laptop to run Windows 10.

It turns out to be a bit tricky, but possible. I had to ignore dire warnings about graphics cards and press on with the installation anyway.. Then, afterwards I found some original drivers and installed enough of them for the automatic Windows 10 update to take over and install the rest. The biggest headache was spending some time trying to work out why the WiFi card hadn’t been detected, only to discover that I hadn’t actually turned it on using FN+F3.

It now works a treat. I’m missing drivers for the SD card and the firewire port, but I don’t need those. As a machine it is pretty responsive. In fact it now books more quickly than it used to. If you have an old machine that you want to rejuvenate, I’d strongly advise you to have a go. The Windows 10 update process has a very good rollback behaviour that means you are unlikely to break the machine and you might end up with something much more useful.

Pick and Mix Nuts and Bolts


I’m building an Air Quality sensor. As you do. I need a variety of different nuts, bolts and washers to hold bits of it together. Normally this would be a pain, as I’d have to buy twenty of something I only need four of.

But now B&Q (the big diy warehouse in Hull) have a “pick’n’mix” display for things like this. It’s like it used to be with the sweets at Woolworths. A full bag like the one above is around two pounds fifty, which is fantastic for making things.

Amazon Echo buttons are surprisingly easy to use


You might thing it’s surprising that I’m this late to the home automation party. What with my love of gadgets and all. I guess laziness trumps gadget love in the end.

However, a few weeks ago, on the back of a really tempting Amazon offer, I got myself a batch of Teckin smart sockets. They fit into your mains socket and then you plug the device to be controlled into them. And then the device is connected to the internets.

A socket can switch up to 15 amps (it says) although I’ve not tried one with the kettle just yet. The only snag with them is that they are slightly larger than a normal mains plug which means that they tend to foul the switch on a wall socket. This is not a problem for me. I’m plugging them into distribution boards, but you might find it irritating.

They work well, once you get over the fact that the lights in your house are now being controlled by a server in China. You can control them from your phone, put them into groups so that they can all be switched at the same time and even see how much current a particular socket is drawing.

So, in no time at all I was in business. Rather than flicking an old style switch I could just get out my phone, unlock it, find the application, navigate to the required group and then tap on the screen. Much simpler. Really. Actually, that’s why I’ve been a bit late to home automation. It actually doesn’t seem to make things that much better.

I made life a bit easier by connecting them to my Amazon Echo device. So now I can just ask Alexa to turn the lights on and that works fine. But what I really want is a button that I can press to turn the lights on. And finally, I’ve got that. Amazon now makes Echo buttons. These were originally touted as a fun way of playing games with Alexa. They are not to be confused with Amazon Dash buttons, which are being discontinued.

I picked up a couple of buttons and they are nicely made, robust devices that connect to your Amazon Echo via Bluetooth. I had a go at the games and I wasn’t that impressed. They gameplay was pretty uninspiring and there was a lot of lag between actions and responses. But you can also use an Echo button as a trigger for a routine. So I’ve made a routine that turns on the lights and bound the button to that routine. It’s very easy to do, you can do it on your phone. The only snag is that there is no way of “toggling” the state of something via a skill. So I’ve had to use two buttons, one for on and one for off. If I write my own skill I can probably get around that, but for now I’m happy and a bit closer to the cutting edge than I was.

Adventures in Colour at the Connected Humber Hardware Group


We had a great time at the Connected Humber Hardware group meetup tonight. We talked air quality, transistor design, top hats (of course) and making colours.

There’s nothing like playing with something to build your understanding of what is happening. Jay has been making remote controlled lights and has built a remote controlled a three colour led. Individual colours worked fine, but mixing them didn’t give the colours that we were expecting. This turned out to be because the individual red, green and blue light sources in the led were all very different in brightness. However after a bit of experimentation with series resistors he managed to get a reasonably balanced result, as you can see above. What’s more this serves as a lovely illustration of how primary colours can be combined to make others.

Great fun. If you want to take part (and why wouldn’t you), our next meeting is on the 3rd of April at 6:00. You can find our more about our meetups here.

Using an Edge Triggered Serial Interface with the ESP8266

The Air Quality sensor that I’m working on uses a GPS receiver and particle sensor. Both these devices use a serial connection to deliver their values into the processor. This poses a problem, in that the esp8266 (the chip that I’m using) doesn’t have very many serial connections. The usual solution is to use a software simulation of a serial port instead of a “proper” hardware one. The difficulty with this approach is that software serial ports slow down the processor because the processor has to stop and wait for each incoming character.

To solve this problem I’ve written an interrupt driven serial port that uses the edges of the serial data stream to trigger readings, which means that it doesn’t hold things up as much. You can find out more in the video above. You can download the code and play with it here.

Amazing facts to impress your friends....

If you want to really impress someone just tell them this:

“If you want to use MQTT with PubSubClient and talk to an Azure IoT Hub over secure sockets you should use Version 2.4.2 of the LOLIN Wemos framework or your program will crash when it runs out of memory during socket open.”

Then again, it might just be me that would be impressed by this.

Building an Air Quality Top Hat and Letting the Smoke Out

smoke out.png

I’m building an Air Quality Measuring Top Hat for my Red Nose Day Lecture in Rhyme next week.

I think I’m the first person in the world to do this. No idea why.

Anyhoo. I’m going to equip the hat with a bunch of coloured leds to indicate the quality of the air around the wearer. Yesterday I started building up the hardware. I was driving all the leds with one of my trusty Wemos 8266 devices. Half way through my first test of the leds I noticed smoke rising from the device. Now, I don’t know much about electronics (obviously) but I do know that all electronic devices are actually powered by “magic smoke”. I know this for one simple reason.

If you let the magic smoke out of a device, it stops working.

It turns out that I hadn’t turned on my main power supply for the leds, so all the power was being drawn through the Wemos device; specifically the blackened and unhappy looking component above. Which got very hot, let out its magic smoke and stopped working.

Oh well.

The good news is that the Wemos devices only cost around two pounds each. I’ve ordered ten more…

Test your hardware before you use it


Here’s a little pro-tip that I could have used yesterday:

Test your hardware before you solder it into your device.

I was using a brand new Wemos device that I just took out of the bag, soldered into place and then fired up. It didn’t work. Closer inspection shows that a wayward surface mount resistor has got underneath another component and as a result the board is useless.

I't’s not a huge loss, I’m only paying 2.50 for my Wemos devices at the moment, but it does mean that I have to un-solder the failed device and solder another in place, which is a bit of a pain. From now on I’m going to test my new device just hanging off a usb connector before actually fitting it. Something I used to do, but seem to have forgotten. Of course, the perfect way to do this would be to test all the devices as soon as they arrive from China, that way I might be able to send back faulty ones.

Oh, and the another thing to hold dear is:

Throw away broken devices. They are never worth keeping.

Once it had its moment of glory under my camera, the failed Wemos went straight into the bin. It looks pretty much perfect in every way, and I guess an expert in surface mount technology could do something with it, but I’m not that person, and I don’t want to confuse it with a working one.

Porchlight 1.0

Porchlight 1.0 is up. I’ve discovered that 16mm cable trunking is perfect for holding lengths of Neopixel leds. So I’ve stuck the lights up over the porch using the adhesive foam on the back of the trunking and we’ll see how it goes. I’m using over the air updating so that I can send new programs into the lights without having to go near them. I’m surprised how well that works.

Haynes Electronic Games Advent Calendar


I got in real trouble a couple of days ago when it was discovered that there still some days from last year’s chocolate advent calendar that I’d not got around eating.

What can I say? I forget stuff.

But this is something quite different and definitely not edible. It’s an advent calendar that starts with a simple circuit that lights a LED and ends up on Christmas Eve with a fully working version of the Simon memory game. Along the way there are some nice little side projects. It’s all made possible by a tiny pre-programmed PIC processor, a breadboard and a bunch of components that make the set not bad value for the price.

The implementation is pretty good, the instructions are fairly clear although I’d liked to have seen proper circuit diagrams as well as the Fritzing pictures that show you where to plug the wires. And, talking of wires, it would have been nice to have had a set of pre-made jumpers of appropriate sizes and colours rather than just a little coil of red wire that will have to be cut and stripped for every circuit. I can see that the effort of making the wires will put off all but the most determined experimenter, and probably also destroy the pair of scissors that are used for the job. At least there is no soldering.

It’s really nice to see things like this coming out though, and I’m going to work through all of the daily exercises while eating each chocolate from my other calendar…

The case of the missing shift key

Can you spot what’s missing here?

Can you spot what’s missing here?

Sundeep got in touch today. She’s looking at getting a very cheap, simple, laptop to develop Arduino software. She asked me what I thought of the GEO Book 1, which is presently on sale at the very attractive price of 99 pounds. It’s got a Celeron processor, a mere 2G of memory and uses rather slow eMMC memory for the rather paltry 32G of storage that it provides.

But it only costs 99 pounds.

I had a look around and the reviews of it were not great, but these reviews were for a device priced at 160 pounds, not 99.

As it happened, I was in PC World buying another hard disk (I’ve run out of space for my photos) and they had the GEO on show. So I took a look.

First impressions were good. The display is fine, the construction smart enough and there seemed to be a reasonable turn of speed. I sneaked behind the rolling demo and fired up Word to get an idea of the performance. Everything fired up reasonably well. Quick enough to be useful. Then I tried to type something and it came out kind of wrong. So I tried again. My text was being mangled. Then I took a proper look at the computer.

There is no SHIFT key on the right hand side of the keyboard. As a touch typist I find this key rather useful. When I type W I use the shift key with my right hand and press w with my left. This did not work. I thought I was going mad at first, and that I’d failed to spot something fundamental. But no. There really is no SHIFT key on the right hand side.

I can’t believe they’ve made a computer like this. I was thinking of getting one of the devices just to see what you can do with a really cheap machine. I had high hopes. But not if I can’t type on it. If you fancy getting your hands on a Windows 10 machine that is so cheap that you could regard it as disposable then I can just about recommend it. But if you want to type properly on the keyboard you’ll need to be careful.

There might be some cunning keyboard mapping code that you could add to steal one of the other keys on that row to work as a shift, and you can of course plug an external keyboard the USB port, but for me I’m afraid that the GEO is a no-go. Even at such an amazing price point.

Learn PCB Design at Connected Humber on Thursday

This could be your design….

This could be your design….

This week we are having a rather special Hardware Group meetup at c4di. We will be looking at the creation of printed circuit boards (PCBs). We will be using a freely available tool which can be used on lots of different computers.

If you have any interest in making stuff you really should come along. It is now very cheap to get PCBs made and they make construction much, much easier. And of course they look really professional.

We start at 6:00 at c4di in Hull on Thursday 15th November. You can join our group on GetTogether here.

Switch Electronics in Hull

Don’t try clicking on the Add to Cart option…

Don’t try clicking on the Add to Cart option…

A while back I had the urge to own some cables that had crocodile clips on each end. They are very useful if only have two hands and you want to connect a bunch of things together. I found some in ebay at a good price, ordered them and they arrived in good time. Just what I wanted. Already found them useful.

Before I threw away the envelope I had a quick look at the accompanying slip. Turns out the company that sent them is based in Hull, around fifteen minutes from my house. I went there yesterday and bought a bunch of stuff.


Since the demise of Maplin I’ve been wondering where I’m going to get all the electronic bits and bobs that I occasionally have a need for. Buying from the internet is all very well, but it does introduce a bit of a delay into projects as you wait for them to arrive.

Well, Switch Electronics have solved all that for me. Their prices are pretty keen and they have lots of interesting components, even a special “Maker” section. If you’re based around Hull I’m sure you’ll find them very useful.