Toothbrush Timer

It has been known since Einstein that time is relative. This seems to apply particularly to children, who can make seconds and minutes seem like days and years when faced with unpopular chores like cleaning their teeth. To get the little dears to spend the three minutes recommended by experts on their teeth, parents concerned for the dental health of their children can resort to electronic means. And so much the better if you can get your children to help out with building the device!

Resistors

R1 = 9-way 1k SIL array

Capacitors

C1,C2 = 22pF

C3 = 100nF

C4,C5 = 10µF, 63V, radial

Semiconductors

D1 = LED, green, low current, 5mm

D2-D6 = LED, yellow, low current, 5mm

D7,D8 = LED, red, low current, 5mm

D9 = LED, blue, 5mm

D10 = 1N4001

IC1 = AT90S2313-10PC (programmed, order code 050146-41)

IC2 = 7805

Miscellaneous

X1 = 4MHz quartz crystal

Case: e.g. Bopla type BOS 503

1 wire link

PCB, order code 050146-1