Home > Circuits > Digital Dice
Modified:20:38, 22 October 2013

This is a neat little circuit in two formats, as a single die and a double version. There is a power down feature that will turn off the LED's after about 12 seconds to save power. The current consumption drops to around 1uA thus extending battery life considerably. The whole circuit should run from a PP3 battery for many months.

This digital dice has a very simple decoding method. It uses the fact that 6 out of 7 dots are paired and then drives transistors from a decade counter to light the LED's as required. This is shown in the table to the right.

When PB1 is pressed the relaxation astable formed by IC1 is enabled. This runs at about 100Hz so the LED's appear flashing but too fast to see the number being displayed. This oscillator drives the 4017 decade counter providing 6 sequential outputs, the seventh is connected to the reset.

The power down circuit is very simple.When PB1 is pressed, the negative plate of C1 is raised to +v effectively discharging it. This sends the output of IC1a Schmitt NAND wired as an inverter, low turning on T1 and supplying current to the LED's. When PB1 is released, C1 begins charging via R2 and the negative plate voltage starts to fall. When it reaches the low triggerpoint (approx 3v), the output from the NAND gate goes high, switch the transistor off. This takes about 30 seconds.


Apart from the centre dot, the others all appear paired with the dot opposite them.


Output 0 A - - -
Output 1 - B - -
Output 2 AB - -
Output 3 - B - D
Output 4 AB - D
Output 5 - BCD

Download circuit simulation on Crocodile Clips
Download circuit simulation on LiveWire
Download circuit diagram - NEW

This version simply has the astable, counter and LED section repeated to form a second independent dice. They both share the same power down circuitry however.

- Download circuit diagram and PCB details

The PCB is shown below, but a better printout can be obtained by downloading the PDF document above.
PCB size = 86mm x 74mm

Designed and Written by Phil Townshend 2005
Back to Circuits page...

www.edutek.ltd.uk - Working Electronics For Students & Teachers