Driving a relay (or other electromagnetic items)

Buck Rogers

Hello!
Does anyone have any ideas for having a BS2 successfully drive a counter (mechanical) who uses a relay style coil to advance? Right now I have it connected to a different board using an SSR to switch it, since the coil voltage is 24V, that in turn is driven using an pair of NAND gate buffers, one connected to the other's input, with a RED LED connected to the output of the first to tell me when it's not advancing.
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Strange no robots here.

Peter Jakacki

A simple N channel MOSFET will do the trick as will a simple NPN too. Just include a diode across the coil. Most 24V coils won't require much current and even a simple 2N2222 plus 1k base resistor will work fine.

Mike Green

Look at Nuts and Volts column #6 (get here).

tonyp12

NUD3124
the 24 indicates that this version's zener is for 24volt operation as this way you don't need freewheeling diode.
http://www.mouser.com/ProductDetail/ON-Semiconductor/NUD3124LT1G/?qs=sGAEpiMZZMshyDBzk1/WizSW%2bwlCH/hM25spW3xjdko=