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Topic: (Mosfet H-Bridge) P-Channel Mosfets are heating up (Read 697 times) previous topic - next topic

Wout01001

Hi all,

I have problems with controlling my Nema 23 steppermotor with a mosfet h-bridge and a micro controller.

First of all my p-channel mosfets are heating up, but following the datasheet it shouldn't. i use a logic

3.3v microcontroller that is connected to a level shifter (3.3v -->5.0v) those pins of the 5v output of the

levelshifter goes to the gates of the mosfets. I use for P channel mosfets (FQP27p06) and for the

N channel mosfets (IRF540N). I want to use 12v ,4amp to control the steppermotor.

I have spent many time on tutorials and forums , hopefully the arduino forum will have a solution.

thank you !

Paul_KD7HB

What did you see on the data sheets that lead you to think there MOSFETS would not get hot?

Paul

Wawa

Steppers need to be driven with controlled current, not voltage.
A common (voltage) H-bridge could deliver too much current to a low impedance stepper, and overheat.
Use a 24volt supply if you want speed, and a stepper motor driver that can handle that current.
The A4988 is $1 on ebay.
Leo..

Wout01001

What did you see on the data sheets that lead you to think there MOSFETS would not get hot?

Paul
On the datasheet of the p-channel FQP27p06: R.JA = 62.5 degrees/Watt
                                                               RDSon = 0.07 ohm
                                                               Max junction temperature = 175 degrees
                                                               Current from powersupply = 4 Amp
So this is how i calculated that they shouldn't get hot: (175 degrees - 25 degrees)/62.5 degrees/Watt = 2.4

                                                                          0.07 ohm *4*4 = 1.12

So 2.4 > 1.12 So i don't have to use a heatsink ? But the mosfets are getting so hot that i can't even touch it.

I don't know what i have to do or change with my circuit ?

thank you for your reply !

MarkT

Hi all,

I have problems with controlling my Nema 23 steppermotor with a mosfet h-bridge and a micro controller.

First of all my p-channel mosfets are heating up, but following the datasheet it shouldn't. i use a logic

3.3v microcontroller that is connected to a level shifter (3.3v -->5.0v) those pins of the 5v output of the

levelshifter goes to the gates of the mosfets.
The datasheet clearly says it will heat up in that situation, as the gate drive voltage is 10V minimum and you
use 5V.
Quote
I use for P channel mosfets (FQP27p06) and for the

N channel mosfets (IRF540N). I want to use 12v ,4amp to control the steppermotor.
IRF540 is not logic level and will also fail to work or heat up.   You said 5V, now you're saying 12V - you need
to clarify, the pFETs will be happy at 12V.
Quote
I have spent many time on tutorials and forums , hopefully the arduino forum will have a solution.

thank you !
In that case you'll know most steppers are current driven, not voltage driven.  So tell us full details of
the stepper motor and we can proceed to chose a suitable driver for it.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Paul_KD7HB

On the datasheet of the p-channel FQP27p06: R.JA = 62.5 degrees/Watt
                                                               RDSon = 0.07 ohm
                                                               Max junction temperature = 175 degrees
                                                               Current from powersupply = 4 Amp
So this is how i calculated that they shouldn't get hot: (175 degrees - 25 degrees)/62.5 degrees/Watt = 2.4

                                                                          0.07 ohm *4*4 = 1.12

So 2.4 > 1.12 So i don't have to use a heatsink ? But the mosfets are getting so hot that i can't even touch it.

I don't know what i have to do or change with my circuit ?

thank you for your reply !
Any internal heat has to go somewhere or else it continues to build. If the leads cannot dissipate the heat, something else has to.

Paul

Wout01001

The datasheet clearly says it will heat up in that situation, as the gate drive voltage is 10V minimum and you
use 5V.IRF540 is not logic level and will also fail to work or heat up.   You said 5V, now you're saying 12V - you need
to clarify, the pFETs will be happy at 12V.
In that case you'll know most steppers are current driven, not voltage driven.  So tell us full details of
the stepper motor and we can proceed to chose a suitable driver for it.
Thank you for your reply ! I have no problems with the irf540N , and i tested the p-channel mosfets with 12V to

the gate. They get hot if the current to my stepper is higher then 1.5 amp. but the required current to my

stepper motor is 4 Amps.

jremington

#7
Jul 26, 2019, 07:59 pm Last Edit: Jul 26, 2019, 08:00 pm by jremington
Quote
I have no problems with the irf540N
You will have problems at 4A draw. Use a logic level MOSFET instead.

If you want to discuss a circuit, post a circuit diagram. Hand drawn is fine.

Wout01001

You will have problems at 4A draw. Use a logic level MOSFET instead.

If you want to discuss a circuit, post a circuit diagram. Hand drawn is fine.
[/quot
You will have problems at 4A draw. Use a logic level MOSFET instead.

If you want to discuss a circuit, post a circuit diagram. Hand drawn is fine.
I build my circuit according to this link : https://en.wikibooks.org/wiki/Practical_Electronics/Stepper_Motors

Do you know logic level mosfet types that can handle 4A current ? And how can you determine the logic level

mosfets ? Thank you !

jremington

#9
Jul 26, 2019, 08:43 pm Last Edit: Jul 27, 2019, 12:08 am by jremington
The H-bridge circuit you linked is just about the worst in existence. It has terrible "shoot through", which means that under certain input conditions, both transistors on one side are on, and the power supply is essentially short-circuited to ground.

Logic level MOSFETs are identified as such on the data sheet and often on a seller's product page, like this one. The parameter you should look for is the lowest possible value of Rds(on) (should be in the milliOhm range) at gate source voltage Vgs = 3V or so.

Circuit at link:

Wawa

...but the required current to my stepper motor is 4 Amps.
At what voltage.

1) Post_a_link_to_your_stepper_motor.

2) Steppers_need_to_be_current_driven,_not_voltage_driven.

Which part of those sentences don't you understand.

Even if your H-bridges would work (they don't), then a simple H-bridge is NOT suited to drive low impedance steppers.
Leo..

Wout01001

At what voltage.

1) Post_a_link_to_your_stepper_motor.

2) Steppers_need_to_be_current_driven,_not_voltage_driven.

Which part of those sentences don't you understand.

Even if your H-bridges would work (they don't), then a simple H-bridge is NOT suited to drive low impedance steppers.
Leo..
Stepper motor link: https://reprapworld.nl/products/motoren_fans/stappenmotoren/nema23_stappenmotor_1_8_stap_30_59_kg_cm/

Ok but what do you recommend , should i just buy a stepper driver ?

Wawa

Stroomsterkte: 4.0
Voltagesterkte: 3.0V
Inductantie: 5.04 ohm

Seems that this datasheet has been written by the same noob.
The numbers don't make sense (to me).
3volt and 5.04ohm works out to 600mA, not 4Amp.
Wise to measure the resistance of the coils, and see if they are actually 5 ohms.
Leo..

Wout01001

Stroomsterkte: 4.0
Voltagesterkte: 3.0V
Inductantie: 5.04 ohm

Seems that this datasheet has been written by the same noob.
The numbers don't make sense (to me).
3volt and 5.04ohm works out to 600mA, not 4Amp.
Wise to measure the resistance of the coils, and see if they are actually 5 ohms.
Leo..
one coil is 14.5 ohm.

jremington

#14
Jul 27, 2019, 05:03 pm Last Edit: Jul 27, 2019, 06:55 pm by jremington
You have the wrong data sheet or product page for that high impedance motor, likely intended for 12V or higher operation.

I agree with WaWa, the data on the product page you linked don't make any sense either. Avoid that seller.

Any cheap motor driver based on the ancient L298 chip should work fine with the motor you have.

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