Archive for July, 2009

Zero Standby Current Timer

Sunday, July 26th, 2009

This is a timer for controlling LED lights powered from a solar-charged battery. It was built to illuminate a passageway between two terraced houses, which is used to move the rubbish and recycling bins from the gardens of both houses to the street on collection days. Power is supplied from a battery charged by a solar panel. To guard against battery wastage due to leaving the lights on, it was desired to have a time switching arrangement where a single push of the switch gives a fixed duration of light before switching off automatically.

The first intention was to use a mechanical time delay switch, but this was found to be a rather costly solution.

The lights themselves were modified from 3-LED, battery powered push lights obtained in packs of two from a pound store (I frequent such places, searching for anything with white LEDs to use in my experiments!) The modification was simple but fiddly; entailing some track cuts to rewire the LEDs from a parallel to a series circuit and bypass the switch, and a resistor change. The timer itself was built inside an MB2 plastic enclosure with a pushbutton switch.

zsbtimer1

Circuit operation is as follows:
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Cygnets

Tuesday, July 7th, 2009

If you’re an ugly duckling
Who grew into a swan
Be grateful it was you who got the breaks.
There are many ugly ducklings
And for every single one
There are fifty handsome cygnets
Who grow up into drakes.