The Programmable Timer (AKA Sagis Timer) was built to stop people from
'just grabbing a 555 and making a timer'. Analog circuits rarely work
correctly with unusual temperatures and conditions.
A balloon payload is :
- swinging and twisting
- Cold, but not predictably
- Subject to RFI from tracking beacon transmitters
- Rarely tested thoroughly before first flight.
A simple, microcontroller attached to a FET switch is a really good timer.
Add a couple of LEDs for status indication before launch, and a 9 ping Female
D connector to attach to a Laptops serial port, (include dropping resistor
please) and you get a timer capable of accurately initiating an event
(cutdown, experiment deployment etc) at a selectable time between 4
seconds and 265 days after the unit is powered up.
