arsal_uet Posted December 14, 2006 Report Share Posted December 14, 2006 hii want to use a realay, to conrtol a bulb of 60 or 100watt using microcontroller ouput.can anyone tel me which relay to be used keeping in view the controling parameter which wold be the dc ouput from microcontroller maximum of 5 volt and the bulb operating voltage which wold be220v ac.thanks for ur replies. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 14, 2006 Report Share Posted December 14, 2006 The output of a PIC has a max current rating of 25mA and then its voltage would be about 4V not 5V.A relay needs 5V at about 40mA or more for its coil so a transistor must be added between the PIC and the relay. Quote Link to comment Share on other sites More sharing options...
gogo2520 Posted December 15, 2006 Report Share Posted December 15, 2006 Hello It depends on the relay on how much voltage and curent you need I sometimes use electronic relays that can be triggerd by 3 volts, not sure how many Mamp's but the Pic supplies enough and the relay can handle 220V at 20amps. A driving transistor works and some will say opto's will do the job too. I guess it all depends on what parts you plan on using. have fun gogo Quote Link to comment Share on other sites More sharing options...
arsal_uet Posted December 15, 2006 Author Report Share Posted December 15, 2006 i have to use atmel 8051 so can u plz tel me in accoradance vid that.thanks. Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 15, 2006 Report Share Posted December 15, 2006 Simply look on the datasheet of the 8051 to see its max allowed output current and what voltage it drops down to (4V?). It is probably only 25mA and the voltage will be 4V.Then try to find a relay with a coil that operates at only 4V and 25mA or less.If you don't find an extremely sensistive relay then the 8051 can drive a transistor that can drive nearly any relay. Quote Link to comment Share on other sites More sharing options...
MP Posted December 18, 2006 Report Share Posted December 18, 2006 Arsal,You don't want to supply a voltage from the micro port to control a relay. Instead, use the micro to sink (drop) the line to 0 V.I use the Opto 22 Solid State Relays directly off the port pin of a micro for industrial control of mains with no problems. You don't need a transistor or any other components on the control circuitry of the SSR. Just your 5 volt VCC and set a high or low on the port pin.You can find what you need on their website at www.opto22.comProduct literature, specs and pricing are on this site, but after you figure out which one you want, search for a better price in your web browser.Hope it helps.MP Quote Link to comment Share on other sites More sharing options...
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