PWM motor controller

[Bob Willson]

Can anyone inform me if this PWM (http://www.ebay.com.au/itm/30A-PWM-DC-Motor-Speed-Control-9-28V-Volt-HHO-RC-Controller-AMP-12V-24V-800W-/130781014794?pt=AU_B_I_Electrical_Test_Equipment&hash=item1e7327eb0a) is suitable for a normal stepper motor, and if so, how it would need to be hooked up?

I have often wanted to use a small stepper for various neat little things (such as drawing curtains etc) and wondered about these.

[Stustoys]

Hi Bob,

I'd have to say "no its not"
First question I think someone that knows what they are talking about would ask is "how many wires coming out of the stepper motor?"

Stuart

[Bob Willson]

4 wires.
Damn, I was hoping it would.

[snowyskiesau]

It's a DC motor driver so won't work with a stepper.

[Stustoys]

Hi Bob,
I assume you are thinking of using steppers as you have them?
There are controllers for less than $7 but I'm pretty sure you need something else on the front end to tell the controller what to do.
New L298N-Based Stepper DC Motor Board Driver Controller Module Robot Car | eBay (http://www.ebay.com.au/itm/190813460494)

How about one of these?
CNC Manual Handle Controller+LED Display for 5-Axis Stepper Motor Driver Board | eBay (http://www.ebay.com.au/itm/190754520411)
For $60 not only can you drive 5 curtains at varible speed but you also have a display of just how far open they are ;)
Damn, turns out you'd need one of these as well which would add another $90 :( (I'd thought it was included)
5-Axis TB6560 CNC Stepper Motor Driver Controller Board MACH3+AU Local Shipping | eBay (http://www.ebay.com.au/itm/190751803918)

Are there any specs on the motor for V and A?

Stuart

[RustyArc]

I'm sure if you hunt around on Ebay you should be able to find a stepper driver with manual pot control. Just make sure it's a "bipolar" driver.

[Bob Willson]

Well so far, it was just a case of 'wouldn't it be cool if I could'. So there aren't any actual motors yet, although I do have a few lying around from previous failures to complete projects. :rolleyes:

I did a few searches for steppers with controller, but everything there seemed to be about +$110.

I may have to give up my dreams of motor driven curtains (or whatever).

[jhovel]

You could try this one: Stepper Motor Speed Pulse Controller and Driver Board | eBay (http://www.ebay.com.au/itm/330549567534)
It has both manual controls for speed and direction - and a jumper to hand control over to a pulse/direction controller (like CNC).
Some personal experience with one of these: works fine, but the heat sink is on the small side and may need a little cooling fan if you go anywhere near the capacity of the board. I guess you know how I learnt that :C

[RustyArc]

This thing here will do what you want:
5V DC 2A Driver Board F 9-40V 6-Wire 4-Wire 2-Phase Stepper Motor 2 Control Mode | eBay (http://www.ebay.com.au/itm/5V-DC-2A-Driver-Board-F-9-40V-6-Wire-4-Wire-2-Phase-Stepper-Motor-2-Control-Mode-/271176604441?pt=AU_B_I_Electrical_Test_Equipment&hash=item3f23629b19&_uhb=1#ht_6121wt_1141)

You use the on-board buttons to first set the desired speed, and then afterwards, the same buttons control the direction. You also have the option to drive it with a step and direction input from a parallel port or microcontroller.

Edit: Wow, Mr Hovel just found the same board. Mine's cheaper tho :)

[Bob Willson]

Thanks to the both of you. Those both look as if they would do the trick. A little on the light side at 2 amps but maybe I need to rethink my size ideas.

[RustyArc]

You can get more power out of steppers by upping the volts - that'll allow you to get more RPMs that you can then gear down.

[Bob Willson]

I placed a bid of $9.90 on the one that you found RustyArc. The most I can lose is that, so if it works then great, if it doesn't then ..... I'll let you know.

[jhovel]

You're a cheapskate Bob! :D
By the way, the two controllers we found fo you are identical - in case you hadn't realised.
Good luck with your bid. :2tsup:

[Bob Willson]

You're a cheapskate Bob! :D

I'm sorry, I don't understand. Is that a compliment or an insult? :)

And yes, I had realised they were the same board, but one was (potentially) a lot cheaper than the other. Although even the cheaper one had a $16.15 'Buy It Now' price

[Hermit]

Bob, do you have any specs on your stepper motor? A sticker maybe? Even coil resistance would help, to determine the power of your motor and whether or not it's capable of the job and if the controller/driver has enough oomph to power it.

A 2A driver won't be gutsy enough for many motors and could overheat or possibly fail very quickly. Even my medium-sized steppers draw more than 2A. (2A is only 10W per coil at 5V). Especially important if you plan to keep one coil energised at times for braking/holding.

As mentioned by RustyArc, you can up the volts from 5V to a bit higher for more power and to allow the motor to be driven at a slightly higher step rate, but again heat can easily become a problem. A motor wih a cast body helps, because it can be attached to a heatsink/chassis to dissipate heat.

[RustyArc]

you can up the volts from 5V to a bit higher

In my case, "a bit higher" would be more like 30V, but that would be with a current-limiting driver, which that one doesn't appear to be.

[Hermit]

In my case, "a bit higher" would be more like 30V, but that would be with a current-limiting driver, which that one doesn't appear to be.

Yep, with current limiting the motor won't actually 'see' a constant 30V, but it allows a much faster initial rise time, improving torque.
Even without current limiting, you can apply over 5V, but usually not much higher without heat problems.

[jhovel]

I'm sorry, I don't understand. Is that a compliment or an insult? :)



It was just stirring - I guess a compliment... that's why I put in the smilie....

Anyway, Rusty made an important point: this driver does NOT have a current limiting facility, so you will have to measure the current with the motor running as you increace the voltage.
The 5V bit has nothing to do with the motor, it is the controller power supply and must NOT be over 5V. I used an old phone charger to provide that voltage. The motor power supply is separate and connected at the other end of the little board, right next to the motor connections. I suggest you try with 12V first WITH A METER connected and see what the current draw is. If it is less that 2A, (if higher, immediately disconnect and try a lower voltage) increase it until it is just below. That will be the most power (torque and speed) you can get out of your stepper motor with that controller. You may find it's enough. If not, then things get a little more complicated, as I don't know of any manual controllers with larger current and current control. The bigger ones all expect to be connected to a pulse and direction control system.

[Bob Willson]

Well the motor I have is labeled XY57STH56-2804B
I know it is a 3 amp motor, Nema 23 and has a double ended shaft.
I believe the last number of 2804B breaks down as follows.
28 = distance from rear of motor to front of shaft in inches (2.8")
04 = number of wires (4)
B = double ended shaft.

Aha, I just found a site that has a description of these motors (http://www.snasda.com/doc/57STH.pdf)

So:-
Voltage = 2.5
Current per phase = 2.8
Resistance per phase 0.9 Ohms
Inductance 2.5 milli Henrys
Holding torque 12.6Kg-cm

[Hermit]

Well the motor I have is labeled XY57STH56-2804B
I know it is a 3 amp motor, Nema 23 and has a double ended shaft.
I believe the last number of 2804B breaks down as follows.
28 = distance from rear of motor to front of shaft in inches (2.8")
04 = number of wires (4)
B = double ended shaft.

Aha, I just found a site that has a description of these motors (http://www.snasda.com/doc/57STH.pdf)

So:-
Voltage = 2.5
Current per phase = 2.8
Resistance per phase 0.9 Ohms
Inductance 2.5 milli Henrys
Holding torque 12.6Kg-cm


That helps. So, since this is a motor intended for 2.5V, it won't work on the 2A driver, even if you apply a 2.5V motor supply. Not without current limiting, at least, since 2.5V into 0.9 ohms is 2.8A. A 1.8V motor supply would work, but with drastically reduced torque.

Sounds like a nice gutsy little motor, (for a stepper). For a curtain opener/closer, I think that a DC motor would be more suitable, with a pair of microswitches for position/limit feedback.

For other purposes, you might find a suitable driver for 3A/2.5V on eBay, since Nema 23 motors are reasonably common, but not as easy to find as a 5V 2A one.
(A higher voltage driver, current-limited at 2.8A, would do it too.) Good luck in your hunt. A couple of years ago I could have made it for you, but my eyes are beyond that lately.

[Bob Willson]

Thanks for that hermit.
Incidentally, a 2.5 volt stepper motor can take up to about 80 volts. I think the general rule is the stated voltage * 40 or thereabouts. My CNC table uses 70 volts unregulated for the steppers.

[Hermit]

Thanks for that hermit.
Incidentally, a 2.5 volt stepper motor can take up to about 80 volts. I think the general rule is the stated voltage * 40 or thereabouts. My CNC table uses 70 volts unregulated for the steppers.

Yep, the actual voltage is irrelevant if the current is controlled. Without current limiting, however, your 2.8A motor would draw 77.8A on a 70V supply. Bang!

[Bob Willson]

As another famous Queenslander is oft quoted as saying ... please explain.

[Hermit]

As another famous Queenslander is oft quoted as saying ... please explain.

I'll try - the voltage means very little, except that with no current limiting, the current will rise to match the voltage following the I=V/R rule, where I is current in amps, V is voltage in volts and R is the effective resistance in ohms.

When there is current limiting, regardless of the applied voltage, the voltage that the coil sees is I x R, where I is the current limit. ie. With 70V applied into an 0.9 ohm coil, with 2.8A current limiting the motor sees 2.8 x 0.9 = 2.52 (volts), it's rated voltage.

I don't think I've explained it real well, but I hope you followed.
(Thinking about dinner. Off to eat it now.)

[Bob Willson]

Zoom zoom zoom

My Head

[Hermit]

Zoom zoom zoom

My Head

Yeah, it's a bit like that.

Put a bit more simply, (now that I've eaten and thought about it some more), in effect the current limiter acts just like a voltage regulator, but adjusts the voltage to allow a pre-defined maximum current to flow by monitoring current, whereas a voltage regulator monitors the output voltage itself.

[RayG]

Hi Bob, Hermit

The easy way to visualise it is to think of a water hose, with voltage as water pressure and current as analogous to flow rate.

So a constant voltage supply is similar to constant pressure, irrespective of flow

And a constant current is constant flow irrespective of pressure.

Stepper motor supplies often use constant current, the higher supply voltage allows for faster switching times and more torque at higher step rates than a lower voltage supply.

Regards
Ray

[Hermit]

Hi Bob, Hermit

The easy way to visualise it is to think of a water hose, with voltage as water pressure and current as analogous to flow rate.

So a constant voltage supply is similar to constant pressure, irrespective of flow

And a constant current is constant flow irrespective of pressure.

Stepper motor supplies often use constant current, the higher supply voltage allows for faster switching times and more torque at higher step rates than a lower voltage supply.

Regards
Ray

That's the way they taught us too - to equate water pressure with voltage.

One small point, though, current-limiting is a little different to constant-current. Irrelevant here.