stuee Posted October 19, 2004 Report Share Posted October 19, 2004 i have attached a what i think is a 120off / 1 sec onCan someone check it over and tell me if its ok.Also is it possible to make it 10 mins off 2sec on, and i need to put a reed switch on it somewhere to turn it on when switches are on.Also with the 120off/1on will it reset back to 120 after the on state.Thanks Quote Link to comment Share on other sites More sharing options...
ante Posted October 19, 2004 Report Share Posted October 19, 2004 Sorry but 24Volts will kill the 555 I one second! Quote Link to comment Share on other sites More sharing options...
stuee Posted October 19, 2004 Author Report Share Posted October 19, 2004 my mistake, ment to be 12v Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 20, 2004 Report Share Posted October 20, 2004 Where is the timing capacitor for the 555? You are using a piece of wire instead. Quote Link to comment Share on other sites More sharing options...
surajbarkale Posted October 20, 2004 Report Share Posted October 20, 2004 You can not get delay in terms of 10mins from a 555. Well not without very large capacitor & similar tolerance. Better use a dedicated timer IC for long delays Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 20, 2004 Report Share Posted October 20, 2004 Hi Suraj,The 555 is a dedicated timer IC. The problem that it has with long time periods is that the timing capacitor must have a high accurate value. Electrolytic caps are not accurate and they have a fairly high leakage current.If you are rich and have lotsa space, you could use 100 or more 1uF 5% tolerance caps in parallel!For years I have been using the CD4060 oscillator/counter IC for long time delays, using a cheap low-value accurate timing cap. I have recently discovered the CD4541 that is much better than the CD4060 because it has a longer divider, built-in powerup reset and a choice of output polarity. It is smaller too (14 pins),http://www.microcontrolador.com.br/datasheets/CD4541.pdf Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 22, 2004 Report Share Posted October 22, 2004 Hi Stuee,Never mind the Instant Messaging, let's let everyone see how easy it is to make a long duration timer with the CD4541.Here is a 5 minute timer where the output goes low after the time period (it can be made to go high if you want). Change the cap for a different time period. Add an RC network and a Schmitt trigger, or another timer to get a 2 second pulse. I got this one from the 1st page of about 77 pages about it on a google search: Quote Link to comment Share on other sites More sharing options...
surajbarkale Posted October 25, 2004 Report Share Posted October 25, 2004 i meant to say "dedicated digital timer" time for mental checkup ;D Quote Link to comment Share on other sites More sharing options...
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