help with 220 volt DC motor

Thread Starter

mohamed Sami

Joined Aug 15, 2015
16
I have a universal motor 220V 1.5A and want to control its speed.
I made bridge to convert 220V AC to DC and transformer with bridge to get 24V DC.

I connected it like this image as R3 is the motor and R2,R1 is potentiometer. I used mosfet IRF644.
Screenshot from 2015-10-20 05:45:30.png
But the motor works with full speed whenever the potentiometer is even if potentiometer is not connected.
So how to solve it ?!
 

Dodgydave

Joined Jun 22, 2012
8,373
You need to connect both negative sides of the power supply together, problem is as soon as the fet gets enough gate bias it will turn hard on, better to use PWM control for smoother action.
 

Thread Starter

mohamed Sami

Joined Aug 15, 2015
16
You need to connect both negative sides of the power supply together, problem is as soon as the fet gets enough gate bias it will turn hard on, better to use PWM control for smoother action.

no change happened the same
 

pwdixon

Joined Oct 11, 2012
488
That FET only has a 20Vmax Vds spec, and the gate voltage limits are +/-5V so you've exceeded that too I'm afraid, it's probably dead by now. OK withdraw all of that now I see you mention a different FET in the text, I was using the one on the schematic.

But then if you used a bridge from 220Vac to dc then you will get a peak of 220*1.4=308V which exceeds even the IRF644.
 

pwdixon

Joined Oct 11, 2012
488
By the way there used to be board rules against posts with rectified mains as it was very dangerous but perhaps they were relaxed in the board rule changes.
 

ScottWang

Joined Aug 23, 2012
6,819
You can change the VR1 and C1 to change the frequency for PWM.
If you don't like to use zener then you also can use 78L12 to be the voltage regulator.

220 volt DC motor_mohamed Sami-01_ScottWang.gif

The mosfet you can choose at least 2 times rating of Vds and 3 time of Id, of course great than more is more better.
2SK2843_Nch_600V10A_540mΩ_Dc2Dc_Motor_Toshiba.pdf
FQA19N60_Nch_600V18.5A380mΩ.pdf
IRFS9N60A-Nch_600V9.2A_0.75Ω.pdf
NTE2995_Nch_600V10A_±30V_Vgs10V_650mΩ.pdf
STW-88N65M5_Nch_650V84A-24mΩ.pdf
 

ScottWang

Joined Aug 23, 2012
6,819
Max :
Using triac on AC for motor will make noise, I was used that for fan, unless change the frequency, if don't care about the noise that it can be used for that.
 

Thread Starter

mohamed Sami

Joined Aug 15, 2015
16
That FET only has a 20Vmax Vds spec, and the gate voltage limits are +/-5V so you've exceeded that too I'm afraid, it's probably dead by now. OK withdraw all of that now I see you mention a different FET in the text, I was using the one on the schematic.

But then if you used a bridge from 220Vac to dc then you will get a peak of 220*1.4=308V which exceeds even the IRF644.
i used the one in text IRF644. ok how to get 220 DC ?
 

Thread Starter

mohamed Sami

Joined Aug 15, 2015
16
If the motor is indeed a universal motor it would be a lot simpler to power it with AC and use phase-control (i.e. as in a conventional light-dimmer) to vary the speed.
it is universal motor but how to control its speed using arduino ?
 

ian field

Joined Oct 27, 2012
6,543
no change happened the same
Did you check if the MOSFET has failed short circuit? - I'm thinking you'd need at least an IRF8xx to handle the voltage - with all that sparking at the brushes and inductive back emf, even that probably isn't enough.

Ignoring back emf and any mains transients, the peak value is somewhere near 320V - your MOSFET has to handle at least that, plus a good safety margin.

Start with a MOSFET that can actually handle the voltage, and protect it from spikes, back emf etc with a MOV.
 
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