MIAC and DC motor

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go233
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MIAC and DC motor

Postby go233 » Thu Jul 21, 2016 10:22 am

I would like to control a DC motor.
It is RS catalog 715-106:
Supply Voltage 12 V dc
DC Motor Type Brushed
Power Rating 16 W
Output Speed 3370 rpm
Maximum Output Torque 75 Ncm
Core Construction Iron Core

Can the MI0235 read the speed and control the power?
(It seems to me that I need to add a motor driver)
Giovanni

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Benj
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Re: MIAC and DC motor

Postby Benj » Thu Jul 21, 2016 12:13 pm

Hello Giovanni,

The MIAC controller MI0235 has a motor driver built in which will allow you to control the speed and direction of up to two DC motors.

As for reading the motor speed or position you will need something like an encoder on the motor shaft to be able to sense the rotation angle and count the number of revolutions.

If you need accurate speed and position control without encoders then a stepper motor may be more suitable. The MIAC can drive a single stepper motor using the in-built motor driver.

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Re: MIAC and DC motor

Postby LeighM » Thu Jul 21, 2016 12:29 pm

Hi Giovanni,
The MI0235 MIAC will not be able to deliver the full power rating of this motor, each channel is limited to ~500mA,
you could parallel up the outputs to increase this (up to a max 1.75A for all channels)
but PWM control would then be difficult, but probably achievable at a relatively low rate via software and timer interrupt.
Do you need 16W, and how many motors, does it need to be reversible?
The new MIAC range would be capable of driving this motor.

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Re: MIAC and DC motor

Postby go233 » Fri Jul 22, 2016 12:42 pm

HI,
I need to drive just 1 motor and I need to reverse the rotation direction.
It has an encoder in-built in it.

If I am not wrong 16W/12V = 1.3 A ! Perhaps is less because the motor efficiency is less than 1?
So, 1.75A is good!
BUT
I am lifting and lowering down a very light weight, so I think I am NOT requesting from the MIAC the full 1.75A
Are transistor output protected by overload and load short circuit?

I don't understand:
1. "....but PWM control would then be difficult, but probably achievable at a relatively low rate via software and timer interrupt...."
low rate? and interrupt?
2. I need to calculate the speed of the motor using the pulses provided by the built-in encoder. Can I do that with the MIAC?

Thanks
Giovanni

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Re: MIAC and DC motor

Postby LeighM » Fri Jul 22, 2016 1:29 pm

Hi Giovanni,
Yes, you can calculate the motor speed from the encoder, but you could do to find out how many pulses per revolution, hence the pulse repetition rate, minimum and maximum range, in order the determine the best way to do this in software.

As you need to reverse, you could only parallel up two outputs to drive in H bridge mode, that would give you nearer 1 Amp, so hopefully OK.
Alternatively you could use all four outputs and a relay for reversing the motor direction, or use the four MIAC relays as the bridge direction control.

Yes, the outputs are overload protected.

To give you speed control (power control) you would need to use PWM.
The MIAC processor has PWM hardware channels that provide PWM control without software intervention (apart from setting up and parameter changing).
But I do not think that there is any way to synchronise these on two channels simultaneously. Hence a software solution for PWM would be needed.
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Re: MIAC and DC motor

Postby go233 » Fri Jul 22, 2016 3:45 pm

ok...
thanks
Giovanni