Room temperature display on big screen is a common requirement from industrial sector. Used in server rooms, PLC rooms, storage rooms and many other places in an industrial units. Traditionally seven segment displays of big size (say four inch height) were used. But now a days DMD (dot matrix display) have become so cheap and easily available that we are tempted to use them in place of old seven segment displays. Following are the obvious advantages that immediately comes to our mind.
- Nicer, fancier and advanced look!
- Less wiring
- Less external components required like ULN IC and transistor.
- Gets ready in lesser time.
- Does not cost too much extra money
(in comparison to 3 units of 12V 4inch seven segment displays wired in multiplexed mode and driven using ULN plus transistors)
Today I will share circuit diagram and program for such an application so that all my readers can make such a display themselves over a weekend. I will use a common P10 32×16 DMD panel to show the temperature. The microcontroller would be my fav ATmega8 which is a 28 PIN DIP packaged MCU available at low cost. Temperature would be sensed by the popular LM35 sensor using the inbuilt ADC of ATmega8.
You can design the circuit on any general purpose PCB or a PCB dedicated to ATmega8. The latter option is easier, cleaner, quicker as less wiring is required. Please notice that we have not used any kind of voltage regulator IC like 7805 in the above circuit, this is because we will use a 5V 6A SMPS to power the system. A 7805 IC can only provide 1A current that is NOT enough to drive P10 DMDs.
For more detail: LED Dot Matrix Room Temperature Display using P10 and ATmega8