|Circuit & PCB designed by Phil Townshend.
Project by Lucy Beck.
This circuit is basically a 37 channel sequencer that will light one LED at a time. The clock is based upon a 555 astable with the addition of an extra RC network. When the 'spin' button is pressed and released, the capacitor charges and reduces the frequency of the astable, eventually bring it to a halt. This simulates the spinning of the ball and it coming to rest on a number.
The LED's are controlled using a multiplex method, where columns and rows are driven high and low in order to produce the effect. A bit of extra logic is needed to cater for the 37th LED since it is an odd number. eg. 6 x 6 = 36. Care is needed when connecting these up.
The whole unit was fitted into a briefcase. MDF with LED's was fitted in the lid along with the circuit board. The base was a vacuum formed shell that had compartments for counters or tokens. These could be placed on the gambling table in the centre.
The battery was a 9v PP3 with a current consumption of around 25mA.