For a couple of recent projects we have been asked to provide interesting and informative display units. We decided to build a unit which can be used in a number of different applications. It was designed to look good, be able to show graphics and text, have a couple of switch inputs and be configurable for a variety of uses. The end result was so useful, we decided to produce this design and a kit of the main parts.
The unit comprises:
- LED dot matrix display
- Interface PCB
- Acrylic hardware
LED dot matrix display
More information about using the LED dot matrix display can be found in this blog post.
To keep development time to a minimum, an arduino is used as the ‘brains’ of the unit. This is a development board based upon the ATMEL 328 microprocessor chip. Our units use the less-expensive Xino, an arduino clone from Ciseco. Any Arduino compatible board should fit into this display unit (except the MEGA range).
There are numerous open-source examples available for the arduino, hence development time is very short. We have developed a simple clock unit with temperature history display as a sketch to get you going with the use of this display, but the final use is left up to your imagination.
A specially designed interface PCB has been produced for this unit. There was some extra space on the interface board, so we decided to add a number of components which might be useful for your project. These include:
- Real time clock with back-up battery
- Temperature measurement sensor
- 2 x input switches
- LED dot matrix display
- Connector for XRF radio transmitter
- Connectors for all the in/out pins
The prototype PCB has just bee made and tested. While it did not work first time, with a few tweeks the unit is working well. Here are some photos:
The XRF can be seen with the white antenna. The coin cell battery keeps the real time clock running.
As usual with a prototype – there were a few wiring changes required…
We now need to produce a production double-sided PCB.
Here is the final circuit diagram for the board:
Right click to save the image for higher quality.
|BT1||BATTERY||20mm coin cell|
|U2||REAL TIME CLOCK||PCF8563|
And the PCB design layout.
****kicad PCB – TO DO, not yet finalised***
The hardware is mainly two pieces of frosted acrylic plastic which are cut out using a CNC machine. The Xino and LED display bolt onto the plastic and spacers are used to hold the two pieces of plastic together.
Kit of parts
Note: The kit is not quite in production yet – please email us if interested.
These are the parts required for this LED display unit:
***image of parts***
Please contact us if you are interested in purchasing a kit of all the bespoke parts.
This project is a work in progress. This is a list of essential and useful changes which need to be made:
- Change 3v3 regulator PCB module – done 30/6
- Use 3v3 as Vref and for temperture – done 30/6
- 1mm holes for buzzer, 20mm battery clip, through-pins for shield – done 30/6
- 1.5mm holes for battery connector – done 30/6
- Remove pull down resistors from RTC – done 30/6
- PCB mounting switch for power – found, need PCB design – done 5/7/11
- Shorter capacitor (it hits the LED display) – done 30/6
- Move regulator away from 20mm battery clip – done 30/6
- Pull up resistor for pin 3 RTC – done 30/6
- Move switches 5mm to right – not doing this 30/6
- Find good switches for PCB mounting (long switch heads) – not using those switches
- Make switch connectors points – done 5/7/11
- Make PCB shorter – done 5/7/11
- Redo PCB as double sided – done 5/7/11
- Order PCB prototype – done 5/7/11 from Spirit PCB
- Build PCB prototype
- Test PCB prototype
- Order real PCB
- Put up kicad PCB files
- CNC files – finalise hole positions