re help with ultra long timing in article apr kuhub cc ukans edu wellison kuhub cc ukans e du writes i have a project that was drooped in my lap that is somewhat a pain to design what i am looking for is a stable ultra long solid state timer what they want to do is to place this thing on the antartic ice shelf and measure the amount of snow fall over a period of six weeks every two weeks they want to trip a selonoid to discharge different colored pellets by gas pressure out across the snow then by digging down into the snow the snow fall amount can be measured as they come to the different color pellets the problem is trying to build a timer that would stand the cold degrees and a power source that wouldn t drain i have looked at the xr timers and the standard ne dual timers but thier temp specs won t go that low also two weeks equates to seconds per firing which means one big timing cap i have found farad yes farad caps that have a working voltage of volts and are small in size but again the time of discharge at or lower degrees isn t linear i was thinking of using several timers chained together to fire the selonid at the end of the timing period but that blasted cold and the drain on a battery over six weeks is the pain one possibility would be to use solar panels but this is during the six month twilight anyone have any good ideas thanks in advance wes just a suggestion take a motorola mc b set it up to give you a pulse once every sec or ten secs with either a rc or xtal clock input then feed to a mc b as clock input and decode output for sec output might have to add a few and gates or decoder chips to get output and reset pulse back to the to restart cycle trigger a oneshot from the decoded riseing edge the one shot then goes to a mosfet to drive the mechanism to fire the pellet launcher these ckts require uamps of current between volts so a volt gel cell of a few amphours would last the six weeks then take the ckt board battery wrap in or of foam or build a box of out of the stuff with plywood or metal exterior build a small heater out of watt resistors in series to keep the battery and ckts warm nd thought use batteries one for heater one for timer and pellet trigger insolate insolate even though the chips state that the al rated devices are good to c the batteries have a considerable reduction in capacity oh make sure the area inside has minium air leakage hope this helps rw is this to long winded for the net be gentle
