Controlling a motor

Thread Starter

huan123

Joined Sep 8, 2020
1
Hi guys,

I am an absolute noob to electronics, so please forgive my stupidity. The thing is, I want to build a project with a motor and I want to program it to spin for some degree, at slow speed then stop for a set time like 5 minutes then repeat the cycle again. I was thinking about using an Arduino. Hope you guys can kindly guide me what to learn, what components i need. I tried to look on online but the resources were so limited. I would appreciate any kind of advice and instruction. Thanks a ton really!!IMG_2923.jpg
 

djsfantasi

Joined Apr 11, 2010
6,811
Are you running the motor at full speed or are trying to control its speed?

If the former, the easiest way is to use a SSR (Solid State Relay). It’s control signal must be compatible with the Arduino pin. That is, 5V 20mA. It’s contacts must be able to power your motor. It looks from the faceplate, that the SSR must switch 230VAC at 2A. The faceplate states 1.08A, but for safety you need the higher rating.

The specific SSR needs to be selected by checking its datasheet. If you can’t match the input specs exactly, I’d use an N channel logic level MOSFET to provide more current to the SSR.

Of course, the programming is another challenge. Do you have programming experience?
 

Irving

Joined Jan 30, 2016
1,017
The TS stated he wants it to run at slow speed - if this was a single phase induction motor a simple dimmer would suffice. But its 3-phase so only a variable frequency drive (VFD) will solve this, the single SSR won't work...
 

Irving

Joined Jan 30, 2016
1,017
Looks like a job for VFD!
Not much good if precise positioning is needed however.
Max.
Depends how precise, but you're right in that CNC servo level precision won't be possible, but lifts, doors and tumblers (where you want it to stop by the hatch) can be managed pretty well - the brake circuit locks the rotor quite quickly..
 

MaxHeadRoom

Joined Jul 18, 2013
21,426
Actually it is done in CNC mills etc that use tool changers with multi-tool magazines with induction motor spindles..
A VFD with encoder feedback is needed, the CNC controller also has to be capable.
Max.
 

Ian0

Joined Aug 7, 2020
491
If I were new to electronics, I don't think I'd start by making a circuit which delivers 180 Watts at 400V AC.
And induction motors are even trickier to control than synchronous motors, because the speed the rotor rotates is different from the speed the magnetic field in the stator rotates.
The rating-plate speed (1350rpm) will be achieved when the magnetic field is rotating at 1500 rpm, and will vary with the amount of torque it has to provide. The difference in speeds is called the "slip".
Irving is correct that the speed can be reduced by reducing the voltage with a dimmer, but the magnetic field is still rotating at 1500 rpm and the reduction is speed is only achieved by increasing the slip until it almost stalls.
 

MaxHeadRoom

Joined Jul 18, 2013
21,426
This is why the VFD is so popular among the DIY'ers for machine spindles because they can operate on 240v 1ph and output a varying frequency 3ph power. for a common 3ph induction motor..
For a DIY VFD project, it virtually requires the use of a Microchip of some kind.
Max.
 

Irving

Joined Jan 30, 2016
1,017
I've part-designed & built my own VFD for controlling a 2kW 15000rpm Chinese milling spindle on my (sadly now moth-balled) high-speed ally CNC router - it's not a DIY project (this was an MSc student project I was supervising). The TS needs to find a cheap fractional HP (0.25HP/500W) VFD with a 0 - 10v control input, a pulse speed-counter output and inputs for brake, soft-start, etc. You can pick them up on eBay for <$50

Or junk that motor and find a smaller single-phase motor and a 400W dimmer (or build-your-own, which is a DIY option).
 

MaxHeadRoom

Joined Jul 18, 2013
21,426
For a first project, a small DC motor with a simple 555 PWM would do what he wants.
Flog the 3ph motor locally and he will be ahead.
Max.
 

Irving

Joined Jan 30, 2016
1,017
For a first project, a small DC motor with a simple 555 PWM would do what he wants.
Flog the 3ph motor locally and he will be ahead.
Max.
Well we don't know what he wants/needs. Thats a 180W/0.25HP motor. We have no idea what torque/revs are needed. A wheelchair motor would be a similar size/output power but thats not going to be a 555/MOSFET job, the controller for that has a 16 MOSFET H-Bridge with a >100A stall current, torque/vector control and compensation to to allow it to start under heavy load.
 

Ian0

Joined Aug 7, 2020
491
Aren't most wheelchair motors permanent magnet brushed DC motors (or has technology moved on)?
If so, MOSFET and 555 will do the job nicely! MIght need a driver IC for the MOSFET, and certainly will need a flyback diode. Changeover relay if reversing is needed.
 

MaxHeadRoom

Joined Jul 18, 2013
21,426
My intention was to mean DC brushed, as opposed to BLDC etc.
The internet is awash with various cheap DC motors.
Agreed the OP needs to specify more details in order to qualify a suitable motor.
There is also plenty of Hbridge modules on ebay L298, LMD18200T etc
Max.
 

Irving

Joined Jan 30, 2016
1,017
A good PMDC wheelchair motor has a winding of around 50mOhm and will easily pull 200A on 24v at stall and 100A on start. A single MOSFET won't come close - I'm working with these motors and controllers on a daily basis.
 

MaxHeadRoom

Joined Jul 18, 2013
21,426
A good PMDC wheelchair motor has a winding of around 50mOhm and will easily pull 200A on 24v at stall and 100A on start. A single MOSFET won't come close - I'm working with these motors and controllers on a daily basis.
As the OP has not specified any details, it is a little premature to introduce a 200a motor at this point.
One source of higher power DC motors with controllers is a local sales site where Treadmills are offered for free, but even these motors are usually in the 2hp to 3.5Hp range.
I am guessing the OP's may be a smaller project?
Max.
 

Ian0

Joined Aug 7, 2020
491
A good PMDC wheelchair motor has a winding of around 50mOhm and will easily pull 200A on 24v at stall and 100A on start. A single MOSFET won't come close - I'm working with these motors and controllers on a daily basis.
IRFP7718 at 195A - now that's pretty close!
 

Irving

Joined Jan 30, 2016
1,017
As the OP has not specified any details, it is a little premature to introduce a 200a motor at this point.
One source of higher power DC motors with controllers is a local sales site where Treadmills are offered for free, but even these motors are usually in the 2hp to 3.5Hp range.
I am guessing the OP's may be a smaller project?
Max.
My point exactly, we don't know. The motor I refered to is similar size to that given but we have no idea what the actual need is. All I was attempting to do was illustrate the equivalent PMDC motor may not be the simple 555/MOSFET solution suggested if that IS the requirement.

IRFP7718 at 195A - now that's pretty close!
Yes, in theory, but given that the motor wiring is typically 10 or even 16mmsq cabling a single MOSFET cannot carry that current continuously through its pins - this isn't a breadboardable solution.
 

Ian0

Joined Aug 7, 2020
491
Yes, in theory, but given that the motor wiring is typically 10 or even 16mmsq cabling a single MOSFET cannot carry that current continuously through its pins - this isn't a breadboardable solution.
Datasheet says:
”Maximum Continuous Drain current (wire bond limited) 195A“, at all case temperatures below 125°C.
 

Irving

Joined Jan 30, 2016
1,017
Datasheet says:
”Maximum Continuous Drain current (wire bond limited) 195A“, at all case temperatures below 125°C.
Oh dear @Ian0 , I'm sure you're not one of those who blindly follows statements on datasheets without understanding what they mean... but for the benefit of others...

A 1.2mm x 0.6mm wire, 5mm long (the external connection) will experience a temperature rise of around 190degC at 80A - so while the wire-bond at the drain and source are able to handle 195A the source pin won't; and the PCB trace would need to be correctly sized too.

The TO220/TO247 package is practically limited to around 75A per MOSFET. For an interesting write up see here
 
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