nickey 0 Posted April 11, 2011 Share Posted April 11, 2011 On my current project I am trying to get the MSP430G2211 to turn on a 12 volt pump for a certain duration. I have all the other logic and coding worked out and done, but I am at an intersection as to how to convert the 3v out signal to control the pump. (see diagram attached).. Do I use some transistor to hit a Power MOSFET (I have an IRF510) and then use that to activate the relay (not sure on how to configure that).. Or do I use the IRF510 or something similar instead of a relay? (never used a MOSFET for anything before).. Or perhaps a better idea yet? thanks.. water pump.doc Quote Link to post Share on other sites
P!-Ro 4 Posted April 11, 2011 Share Posted April 11, 2011 Use a multimeter to check the current draw of the relay. If it is under 200mA, which it probably is, you could just use a simple npn3904 transistor. You can buy one for over a dollar at radio shack, or you can stalk up dirt cheap from here: http://www.taydaelectronics.com/servlet ... 904/Detail When I order they usually take a little over a week to the U.S., so keep that in mind if you are in a hurry. You will need to look at the datasheet for it to know which pins are which (be careful, if set it up wrong you may accidentally drive the relay from the I/O which will destroy it) but if you would like I can see about finding you a schematic tomorrow if you need one. Quote Link to post Share on other sites
jsolarski 94 Posted April 11, 2011 Share Posted April 11, 2011 I would like to add that a 2n2222 npn transistor would work as well As for the FET http://www.irf.com/product-info/datashe ... irf510.pdf I dont think is suitable for this application. Quote Link to post Share on other sites
zeke 693 Posted April 11, 2011 Share Posted April 11, 2011 Take a look at this google image search for relay driver circuit. There's some pretty good schematics that come up. You will see a theme amongst them all. An NPN driving a relay. Hopefully, one of them will click with you. nickey 1 Quote Link to post Share on other sites
MystBoy 5 Posted April 11, 2011 Share Posted April 11, 2011 my prefered way driving relais is with an optocupler!! it has a lot of advantages like you can use any relais like 3v 5v 12v cause you are independent of your uC's voltage you don't have to calculate if your transistor will fit just take a relais an optocupler and a diode and the relais... driving an optocupler is simple, cause it's like driving a led you can also have also seperation of the switching and the controlling circut if you want to... i think it's a much simpler and more flexible way to drive a relais and i think the pirce doesn't matter cause an optocupler is like 20c i have a layout with 4relais 4optocupler and 4 leds for optical visualisation... if you want i can give it to you, but i have never tested it, but ill soon do so! Quote Link to post Share on other sites
nickey 0 Posted April 12, 2011 Author Share Posted April 12, 2011 Thanks zeke for the nice pointer to all the relay circuits.. I actually ended up copying one of them for my circuit (now posted in projects). As for mystboy and optocupler, thanks for the idea but it looks like I have found a solution with the parts I have on hand. Quote Link to post Share on other sites
MystBoy 5 Posted April 12, 2011 Share Posted April 12, 2011 if you have the parts on hand it is clear you don't want to wait for shipping some optocuplers after i etched the layout and tested it i'll release it on the forum along with the whole project... Quote Link to post Share on other sites
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