Electronic dice with 7 LED

Posted on Nov 21, 2012

This project takes advantage from -HOLD input, which is connected to push-button P1. As long as the -HOLD input is low, truth table's timeouts have no effect because this input serves to disable any state change provoked by timers. The effect is to freeze Nutchip's counting, stopping the LEDs on the number they were displaying at the time of key release. Notably, we could have used -STOP input to get the same effect, although this does not apply as a general rule - there are occasions where these two pins behave differently. A 390 ohm resistor (R5) keeps -HOLD pin at low-level when P1 is released: so the numbers do not change and the LEDs display steadily the last number drawn. When pressing P1, the -HOLD input goes to +5V because of the button's action - ovverriding R5 effect. Nutchip timer is no longer blocked and it keeps changing state at a fast rate, giving a random rolling effect as long as P1 is pressed.

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At first glance, the way the LEDs are drawn can look messy. Don't be fooled by appearences - the schematic is drawn to simplify breadboarding, and the way the parts are placed reflects the actual solderless breadboard prototype. Follow carefully every connection to discover that we have just three LEDs pair connected to outputs OUT2, OUT3, OUT4 and a looney LED connected to output OUT1. This circuit is suitable for breadboard assembling. The photo shows how to place the parts on a solderless breadboard. The process requires careful LED placement, in order not to reverse or exchange them. All of the LEDs have their cathode pin towards Nutchip, except the mid one (#7) whose cathode is faced up. Common LEDs have their case flattened in proximity of cathode pin. Also, LEDs have the pins divaricated enough to allow an extra bradboard hole between them. E.g., LED #2 anode goes to red wire, and cathode to yellow. The green wire is routed through.. We suggest you to temporarly modify the truth table increasing timeouts to 2 or 3 seconds (in place of actual 30 mS) in order to perform a circuit test - and to understand fully how the circuits works and reacts to user action! Chip programming is easy: if you have an interface like ours, plug it into breadboards holes, they are highlighted with a red border and a "PC" label in the photo. Right after table programming, the circuit is ready to work. Press P1: as long as you keep it...

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