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This is a large visual temperature display which can be used as an alert if a temperature set-point is reached.

It was built for a friend who has a laser cutter and needed to keep an eye on the coolant temperature. The cutter was not meant to be run with coolant temperature above 25°C. If the temperature goes above 25°C then the unit will ‘bleep’.

It uses the large 7-segment displays, a minimus AVR and a Dallas 1-wire temperature sensor, all within a mountable laser-cut plywood enclosure.

If you would like one for your laser cutter set-up then you can also buy one built and tested for £30.

The full build instructions are here, along with the software code used.


Here are some photos of the unit in action. It runs from 12V DC (provided in this case from an old plug-in power supply)

Set up with the laser cutter (a model from HPC lasers).

Here is a video of it in action:

Here are some more photos of a unit added to the Nottingham Hackspace laser cutter.

Buy it now

If you would like one, then I can also supply them ready-made and tested for £30 including p&p within the UK (afraid this does not including 12V power supply).


(I’m also thinking about building a unit with a relay output to control a pump or chiller – let me know if you would be interested in a unit with that function.)


The unit is based upon a minimus AVR microcontroller development board (see my blog post here for full details about getting it running). This reads a Dallas 1-wire DS18D20 temperature sensor (more info about that here) and outputs the data to two large 7-segment LED displays. There is also a 12V to 5 5V converter (using a standard 7805 regulator) and a piezoelectric buzzer for the output.

I have drawn the diagram here as a visual wiring diagram, rather than a circuit schematic. Hopefully it is obvious with regards to component orientation. As you can see, there is a small additional circuit done on strip board. I will hopefully change this to a PCB on which to mount the minimus AVR.



The enclosure was designed using this method, using T-nut holders so it can be disassembled quite easily. The enclosure was built from 3mm ply-wood, with a 3mm acrylic diffuser for the 7-segment display. Here are .pdf images of the design, along with .dxf to download.

Download the PDF file .

Download the .dxf file for the wooden parts (3mm plywood) here. The .dxf for the plastic parts (3mm acrylic) is here

Minimus AVR / Arduino software

The minimus AVR was programmed using Atmel Flip using code written within the Arduino IDE. Lots more details are in this post.

The Arudino code is quite simple and is shown here, and also for download to install into your sketch folder here. It is based mainly upon the OneWire Temperature example. The temperature set-point can be adjusted within code for other applications.


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