To determine minimum cost possible you will have to define the accuracy to which you need to define the time periods - in particular the delays from initiation to turn on and then from turn on to turn off. Seeing you say date/hour/minute you are presumably happy enough with accuracy to better than 1 minute resolution. Is this over a day, a week or a year (etc). With a crystal you can get seconds per day without much effort if temperature extremes aren't severe and the same sort of performance using temperature correction (either external analog or using the PIC itself "digitally". The latter requires inputting a temperature parameter to the PIC but MAY be able to be done using a cheapish thermistor. Ceramic resonators are cheaper than crystals but are less accurate. resistive clocks are worst of all - but very cheap. An accuracy of say 1% with a resistive clock (which would probably require some work) would give you an error of almost 15 minutes. No doubt there are people here who can tell you how to improve this but it is unlikely that you will get what you want without crystal or ceramic resonator. The cheapest device is 12C508 which is about $NZ1.20 in quantity which is about $US0.70. (or less?) It has all the processing power you need (but no A2D if you want to measure temperature so you would have to do it some cheap and clever way). Programming could be from a Palmtop with an appropriate custom programmer (or maybe someone is doing this already). -----Original Message----- From: Steven Coles To: PICLIST@MITVMA.MIT.EDU Date: Saturday, 7 March 1998 22:14 Subject: HELP on programable timer! >Need 20,000 timers that I can preset to go on at a certain >date\hour\minute (energize solenoid A 5 seconds to open my device) and >off on another date\hour\minute (energize solenoid B 5 seconds to close >same device). Ideally I would program the timer with a Hewlett Packard >palmtop via the inferred port to speed programing and avoid tampering. > .... Email is best to; arids@uswest.net >