LED display unit
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
- Microprocessor
- Interface PCB
- Acrylic hardware
LED dot matrix display
We are using a 32 by 8 LED dot matrix supplied by Sure electronics, based in Hong Kong. They also have an eBay shop. The price ranges from $8 to $16, check eBay first.
More information about using the LED dot matrix display can be found in this blog post.
Microprocessor
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.
Interface PCB
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
- Buzzer
Prototype PCB
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:
Disconnected boards – Sure LED display, my shield prototype PCB including XRF module,and Xino, the ardunio clone
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.
Parts list
| Schematic REF | Component | Value |
| BT1 | BATTERY | 20mm coin cell |
| BZ1 | BUZZER | Piezo element |
| C1 | CAPACITOR | 100n |
| C2 | CAPACITOR | 10u |
| C3 | CAPACITOR | 100n |
| C4 | CAPACITOR | 100n |
| D1 | DIODE | 1N4001 |
| D2 | DIODE | 1N4001 |
| D3 | DIODE | 1N4001 |
| MOD1 | WIRELESS MODULE | XRF-00 |
| P1 | CONNECTOR | BATT |
| P2 | CONNECTOR | CHARGER |
| P3 | CONNECTOR | CONN_8X2 |
| P4 | CONNECTOR | CONN_6 |
| P5 | CONNECTOR | CONN_6 |
| P6 | CONNECTOR | CONN_8 |
| P7 | CONNECTOR | CONN_8 |
| R1 | RESISTOR | 5R 3W |
| R2 | RESISTOR | 10k |
| R4 | RESISTOR | 10k |
| R5 | RESISTOR | 10k |
| R6 | RESISTOR | 1K |
| R7 | RESISTOR | 1K |
| SHIELD1 | ARDUINO_SHIELD | |
| SW1 | POWER SWITCH | SPST |
| SW2 | INPUT 1 | SW_PUSH |
| SW3 | INPUT 2 | SW_PUSH |
| U2 | REAL TIME CLOCK | PCF8563 |
| U3 | 3v3 REGULATOR | MC1703 |
| U4 | TEMP SENSOR | MCP9701 |
| X1 | WATCH CRYSTAL | 32.78kHz |
And the PCB design layout.
****kicad PCB – TO DO, not yet finalised***
Acrylic hardware
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.
The design for the plastic was produced using HeeksCNC, the design file is available here. The output g-code is used on our desktop CNC machine run on an Ubuntu machine using EMC2.
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***
Prototypes of this design have been used in our solar race timer and remote power and energy display.
Please contact us if you are interested in purchasing a kit of all the bespoke parts.
To Do
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
Sarei interessato alla realizzazione di questo kit.
Grazie per una cortese risposta, Giorgio Smith
I am sorry but this kit is not yet available but hopefully there is enough information here to build your own. Regards. Matt
Mi dispiace, ma questo kit non è ancora disponibile, ma si spera ci sono informazioni sufficienti qui per costruire il proprio. Saluti. Matt
I want one kit