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..
Paul_KD7HB:
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 44 = 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 ?
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.
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.
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.
Wout01001:
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 44 = 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.
MarkT:
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
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.
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..
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..
Please remeasure this, it cannot possibly be true if its genuinely a 4A motor as stated.
I would expect 0.5 to 1.0 ohms or thereabouts. Much more and the motor would overheat and catch fire at 4A.
The figures suggest its a 0.75 ohm motor.
To drive a 4A motor you need an industrial stepper driver, there is no single-chip solution to this current level.
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..
The inductance is clearly nonsense as the units are wrong, best to ignore it, perhaps its meant to be mH.
