Which Transistor to Use to Drive 3.4 Ohm 28v Solenoid?

I'm attempting to drive a 3.4 Ohm 28v ball return solenoid in a pinball table. If my math is correct this will draw 28/3.4 = 8.2 amps. The TIP122 however is rated at 5 amps max.

What is a more suitable transistor?

My research has shown perhaps:

  • TIP141
  • IRFZ-48
  • TIP35c

Of the three the TIP141 is the only option.

  • The TIP35c has an hFE (gain) of 50. 20ma Arduino pin current * 50 = 1A and that’s not enough.
  • The IRFZ-48 is not a logic level mosfet. It might work but it’s designed for 20V at its gate. Keep in mind that “IRL” mosfets are Logic Level, “IRF” are not.

There are assuredly millions of better options out there; I’m just answering with respect to the three you’ve listed. You should be looking for a logic level mosfet.

The TIP141 will work. It is a darlington transistor, and might get hot. The IRFZ-48 is not a "logic level" mosfet. It is fully "on" at 9V or 10V. You need a mosfet that is "on" at 5V. The TIP35c needs an extra transistor to get enough base current. At 8A, the Hfe is about 80, so you need 100mA base current.

The normal transistors are so 1970's. I suggest to use a "logic level" mosfet, or a relay.

Sparkfun and Adafruit have selected these: https://www.sparkfun.com/products/10213 http://www.adafruit.com/products/355

I just buy a bunch of the cheapest TO-220 n-nchannel "logic level" mosfets on Ebay. http://www.ebay.com/sch/i.html?_nkw=mosfet+logic+to-220&_sop=15

(while I was writing this, Chagrin wrote the same)

He has been told that already:- http://forum.arduino.cc/index.php?topic=311480.msg2161187;topicseen#new

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