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Transistor get's really hot and doesn't seem to work. Answered

I'm trying to turn on and off a 12V dc motor/pump (it's one of the motors that squirts the water on your windshield to clean it). Just hooked directly up to the power supply it draws about 1.5A. When I turn on the switch, my transistor gets super hot, to the point I can smell it burning, and the motor does NOT turn on. It's an IRF510 transistor. I copied this circuit from a YouTube video (https://www.youtube.com/watch?v=-g0Q0e1mhIY&feature=iv&src_vid=nYjhYKeOOgI&annotation_id=annotation_856844) and this guy seems to have gotten his version to work fine. I cannot figure out what's going on here.

The wires in my picture that go off the table are connected to a 13V power supply on the ground. The diode attached to the motor is a 6A rectifier to handle the emf surge from turning the motor off.

Let me know if you have any questions for me!

IRF510 Datasheet: http://www.kitsandparts.com/IRF510.pdf

Discussions

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Zamperweenie

3 years ago

Anyone else running into this issue check out this reddit post:


https://www.reddit.com/r/arduino/comments/3gedc5/controlling_12v_dc_motor_with_an_irf520_transistor/

/u/bal00 does an awesome job at explaining why I was having this issue and offered a solution (that worked!). The short answer is that everything was hooked up correctly, just the transistor wasn't the right kind for this project.

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iceng

Best Answer 3 years ago

The IRF 510 does not turn on the 1.5A with a 5v Vgs signal !

In fact, the IRF 510 needs over 5V Vgs to turn ON 1.5A ..... and since a dc motor pulls 5 times the motor starting current 7.5A the IRF 510 a peak of 5.6A transistor is underpowered and under gate driven !

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Zamperweenieiceng

Answer 3 years ago

That makes sense! After looking around I think I'm going to replace it with an NTE2395 MOSFET. It seems it'll dissipate way less heat and everything else seems to be rated alright.

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Wired_MistZamperweenie

Answer 3 years ago

Can't Hurt ! :P

Still feel I should point out that the Vid you linked to uses a Tip120. I rarely have problems with the tip-12X Chipset

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seandogueiceng

Answer 3 years ago

+1

Partial turn-on makes the FET into a resistor, and resistors dissipate energy in the form of heat. For full turn-on at spec'd on resistance values, most N channel devices want the gate at com, and for P channel FETS, gate at rail

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Wired_Mist

3 years ago

Flip the Fly-back diode over.

That little line represents the negitive side. The line has to face VCC (Positive End)

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ZamperweenieWired_Mist

Answer 3 years ago

Yep, I did have that backwards! The 6A diode was overkill I learned. I simple 1A or so diode is fine (I switched to an IN4007), because all that matters is what *current surge* the diode can handle, not the *continuous current*.

A 1A diode can handle a pretty hefty current surge, way more than what I get here. Also the 1A fits on the breadboard so I could place it in parallel with the motor on there instead of clamping it to the motor. Less tacky and easier to see the circuit that way.

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icengWired_Mist

Answer 3 years ago

Oh .... I see what you mean that diode is a short from the plus side.

If the mosfet does not melt first, the diode which looks like a hefty 6A unit might burn out ! ...... Then the motor might run.

It would be better to remove the diode or switch the green and yellow motor clip leads if the motor turns correct.

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icengWired_Mist

Answer 3 years ago

DC current flows in the direction of the line but not back.