Bellow, I’ll present you a simple Count Down circuit implemented with an ATMega32 microcontroller and a HD44780 based LCD display. Yes, i know… it’s maybe in 2018 a bit deprecated, but I think it’s unneccessary to overcomplicate the whole thing with fancy TFT-Displays and so…
The story started at work. We needed something which is flashy signaling, if a setted time is out. You may ask already: “Man, what’s wrong with you? There is your Phone, just use it! “.
Yes, you are right, we tried it, but sometimes we didn’t noticed if the phone was vibrating – and then we had sometimes big troubles because of this.
So we had the idea, we mount somewhere a big flashy lamp, and a simple circuit will switch it on if the time is out. This little thing had to be mounted on the front panel of several switch cabinets, and because of the harsh conditions I decided for a HD44780 based solution, because it should last forever – and plus yet one day.
Okay, it’s enough about the boring story, let’s see what we will be talking talking about. The schematic tell you soon it is really not overcomplicated. Four pins are used as inputs, where are the those push buttons connected with them you control the device.
There is also a signal output, where is a simple 5V relay connected, this will switch our big flashy lamp on. Besides, there is a very simple power supply, the LCD, and that’s it…
To make something out of it, we need a PCB. If it is not urgent you let it make by JLCPCB, otherwise you make it at home – as i did – but in this case it will be maybe a bit ugly.
As you can see, the transfer of the paint was not everywhere the best, but it should be okay for now.
And it looks like so after etching the PCB.
After that, you have to drill your PCB, and you can begin with the placing of the parts, then soldering them, and at the end you can just try it if it works. Bellow are two very simplified gifs about the function of the device.
Wile counting down…
… and after the time is out, and the relay was switched on.
Because it will be mounted on the front of a switch cabinet, we also need a front panel. This was made with a 3D printer. Well, it’s not so fancy designed like an iPhone, but for us should be good enough. Especially if it will be coated with some paint.
Course, it’s not the nicest device you ever seen, it can be done more prettier – if you have tools and resources – but it demonstrates perfect how with just a little bit more effort you are able to create more complex things, and if you are creative you can even invent such solutions which may not exist yet.
If you want to build this circuit, feel free to get the source code and the PCB from my github: