TIP102 vs TIP120?

Are these transistors interchangeable? I am trying to drive a relay from a digital out on the Arduino.

Thanks in advance!

http://www.fairchildsemi.com/ds/TI/TIP102.pdf
http://www.learn-c.com/tip120.pdf
Here are the data sheets.

The short answer is yes. And I found the data sheets on my own… they just don’t mean anything to me. It might as well be written in hieroglyphics.

The TIP102 has a Vceo “collector to emitter breakdown voltage” of 100 VDC as aposed to 60 Volts for the TIP120. thats pretty much the only major difference. switching anything under 40 Volts, i would just use what ever you find easiest to get your hands on.

David

Also, do you really need a Darlington transistor? any relay that requires less than 200 mA can be driven with an ordinary GP “general purpose” NPN like a 2N2222 or a 2N4401. look for the Hfe specification on the transistor data sheet. Hfe is the DC current gain. A transistor with a minimum Hfe of 80 will draw less than 2.5 mA from the pin of the micro controller while driving a relay coil that needs 200 mA to close. The TIP102 has a minimum Hfe of over 1000 and would close a relay that required over 2 amps without drawing 2 mA from the micro controller pin.

El cheapo relays that I had laying around were 9V. 5V signal from arduino to Tip120 to switch the 9V for the relay. I’d have bought 5v relays if r$ had them in stock.