How to Amplify a 2.5 mA Pulse to Drive a Latching Relay?

[jbord39]

Hey. I am trying to use a single quick pulse of about 2.5 mA to run a latching relay. I know that this signal needs to be amplified (probably with a transistor) but am unfamiliar on how to do this.

Thanks for the help,

John

 

[waht]

Here is a relay driver. The diode in this circuit is used to protect the transistor from high voltage that is being induced by the relay coil.


http://www.vlearnvshare.com/home/images/articles/NPN-DRIVER1.GIF

 

[Bob S]

If the relay current is over 50 milliamps, you should use a Darlington transistor, such as the TIP120 (available at Radioshack) or equivalent. See datasheet

http://www.learn-c.com/tip120.pdf

The current gain at saturation is ~250. You should also have a 10k resistor from the data input to ground.

Bob S

 

[jbord39]

Thanks for the help. I'm going to get the parts today so I'll let you know.