Looking for a stepper motor controller
w4fej
Posts: 264
I recently purchased a brand new type 23 stepper on Ebay and it was listed as a 6 amp, bipolar, 1.8 degree stepper. Anyone know of a controller that can handle that much current or a design (read schematic) to build a board from..
I see many on Ebay using the L293N but the chip is rated too low for my app. The stepper will only be used to turn a rudder which actually a trolling motor so it won't be seeing long runs, only short bursts..
Any hints would be greatly appreciated.
Thanks, Mike Blier
I see many on Ebay using the L293N but the chip is rated too low for my app. The stepper will only be used to turn a rudder which actually a trolling motor so it won't be seeing long runs, only short bursts..
Any hints would be greatly appreciated.
Thanks, Mike Blier
Comments
ones, Gecko Drives are one possibility and cheap chinese ones from eBay.
You definitely _don't_ want a quad-half-H-bridge, that's worse than useless for this kind of motor. You always
use a current-controlling chopper drive for this kind of stepper, often from 40 to 100V supply (to give good
speed). For slow speed use a chopper drive from 12 or 24V will be quite sufficient.
What's the winding resistance BTW - somewhere around 0.6 ohms I'd guess. If so 4V would overload the windings,
these motors are designed for current-control, not voltage control.
Why choose a high performance bipolar stepper for this application, BTW?
Thanks guys for the reply's..
The motor specs are 12 VDC @ 6 amp.. The motor that actually came with the trolling motor is a SMALL 12vdc geared motor that handily turns the trolling motor no problem. The reason I am looking at the stepper is that I want feedback to know the actual position of the rudder/motor. I was originally thinking of an optical disk interrupting a LED source/sensor device but thought the stepper would be easier. The optical disks turn out to be pretty hard to make your own.
BTW the application is a large scale R/C tug boat about 6 foot long. I'll be using an Xbee data link to/from the boat and a touch screen controller in the handheld unit..
I envision the trolling motor only turning + - 45-50 degrees. I have a 7.1:1 belt drive system to turn the motor. 72 teeth on the big pulley and 10 teeth on the motor/stepper. I only have $13.00 invested in the stepper and not opposed to changing up to a better/easier solution to turning the motor. Feed back from the rudder position is a must however.. Oh yea, I'll have an index mark on the big pulley for rudder midships..
Mike B.
They interface easily with the Propeller over three inputs --- Pulse,Enable, and Direction. You have to setup a bunch of DIP switches to the micro-stepping you desire.
I find that 6amps is a bit hard to find a controller for on EBay. 3 amps seems more realistic.
Take a look at your original vendors website for a possbile easy fit. Just because the motor is rated at 6 amps doesn't mean you have to drive it at that high a current.
If this is all going in a r/c boat, weight is going to add up quickly between batteries, motor controller, and stepper.
http://www.ebay.com/itm/TB6560-CNC-Stepper-Motor-Driver-Board-Controller-3-Axis-/181301062665?pt=LH_DefaultDomain_0&hash=item2a3662ac09
http://www.cnc4you.co.uk/index.php?route=product/product&product_id=29
I rather doubt it - measure the winding resistance - it its more like 0.5 ohm than 2.0 ohm (I suspect
so) that means the "12V" spec is specious. Do you have a link for the motor?
Well I don't know anything about the company I got it from but it isn't in China but rather in California. Here is the item I bought:
http://www.ebay.com/itm/NEMA-23-CNC-Step-Stepping-Stepper-Motor-6-0A-152-oz-in-Bipolar-200steps-rev-/171192658511?pt=LH_DefaultDomain_0&hash=item27dbe0aa4f
@kwinn
I thought about using a pot and still might. I have all the mechanical stuff to use that motor and it would be a simple matter to add a pot in the mix with the cog belt/pulley arrangement.
By the way, one of the replies commented that the size and weight would add up quickly. The boat is nearly six feet long and the all up weight is in the neighborhood of 175 pounds so space and weight isn't a concern..
By the way, the whole purpose of this drill is to get position information that a Prop can read and send that info back to the handheld controller so I can display the rudder position on my touch screen.. If there's a better mouse trap (than the stepper) out there I'm all ears...
Mike B.
Stepper motors are not married to one voltage. If the combination of voltage and amps doesn't create too much heat that burns the enamel insulation off the coil wires, a higher voltage works well. In many cases, the copper wire with enamel insulation will handle hundreds of volts if the current is small enough.
So what is this 12V at 6 amps. Well that equals 72 watts or a bit lower than 1/10th of a horsepower. If you used 24V at 6 amps, you would end up with roughly 1/5th of a horsepower out of the same motor. And I do expect that it will handle up to 36 volts... but since watts is an indication of heat generated, you might want to keep the combination of 12 volts and 3amps in line with 72 watts maximum.
In other words, at 24 V, have the stepper motor controller only deliver 3amps max to any coil. Or at 36v, have it deliver only 2 amps max. And as long as you are being conservative, why not start out with even less heat and deliver 5amps at 12 volts, 2.5 amps at 24 v, and so on. It is the heat that damages the motor, and that is tied directly to how many watts the motors coils draw when holding a step in place.
This has the added bonus as you don't have to put out more bucks for a bigger stepper motor controller that might just burn up the coils in your stepper motor.
I showed a link for a 6amp controller, but it requires 20 volts minimum to operate. If you really want 12 volt operation, you will have to look for another. On the other hand, it might be easier to find a 3.5 amp 12 volt stepper motor driver that won't abuse the motor... but will provide less overall power. The coils just may not have to hold at 72 watts for your project and you will actually drain your battery less quickly.
Face the reality that absolute maximum figures are there for preventing damage and NOT to be the optimal peek operating condition.
It really is all about fitting together, the voltage supply you have available; the stepper motor, and a stepper motor controller.. with reasonable costs.
Hanging too much of 12volts at 6amps is likely to get you nowhere.
The link to the motor's website says the motor will operate from 3 to 36v and up to 6amps peek. So it can deliver at 36 volts x 6 amp or over 200 watts of power consumption. That might get very hot, but not break. But running cooler is always a better choice. And running a DC motor at a higher voltage will always deliver more power with less waste.
And here is a link for a 4amp stepper motor driver that ranges from 12VDC to 50VDC for $36 USD. Basically you provide a 12VDC input and then the device limits the current output as set. It won't deliver a full 6 amps, only up to 4 amps... but you can also have it deliver less via settings.
http://www.ebay.com/itm/Stepper-motor-Driver-50V-4A-128-microstep-stepper-motor-driver-/300943326851?pt=LH_DefaultDomain_0&hash=item46119ebe83http://www.ebay.com/itm/Stepper-motor-Driver-50V-4A-128-microstep-stepper-motor-driver-/300943326851?pt=LH_DefaultDomain_0&hash=item46119ebe83
If that is the case then the simplest approach would be to use a photointerruptor to detect when the motor is oriented in the zero/default/index position (usually straight ahead). On powering up the trolling motor would be turned back and forth until the photointerruptor detects the index position. Once that is done it is only a matter of counting steps and direction to the steering stepper motor for positioning. Just about any photointerruptor would work.
They have a 300 degree range of travel that can be set from position 0 thru position 1023 and the current position can be read back. There are objects in the OBEX to talk to these servos. Maybe overkill for what you are doing.
NOW THAT"S COOL !!!!
Gotta go to work now but I will check out the doc's when I get back....
Thanks for that info, I just might give up the belt drive stuff to turn the rudder/motor in favor of one of these guys....
Mike B..
AX12 has feedback for position, speed, directional torque(sort of), temperature and supply voltage.
Hi Dave:. Wow, that device is perfect for the job and eliminates a lot of junk in the boat.. Even if the servo doesn't have enough torque to turn the motor I could fix the position of the motor and build a "real" rudder and control it like a typical R/C control surface.. (Printing out the manual now).. Headed to the OBEX to check out the objects for this thing..
Mike B.
I guess you now understand that 6 amp NEMA23 steppers really want to operate at higher than 12 volts.. likely 24 or 36. And that 6 amp stepper motor controllers get rather large due to heat sinks and required cooling and are hard to find for operation below 20VDC..
I love to have all that power, but it works better with stationary devices that are connected to mains.
Yep, it became clear pretty fast that this stepper wasn't right for the application. The servo yjay Rat turned me onto looks perfect for the application and again if it won't turn the motor then a real rudder is in order..
Mike B.