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toozie21
01-01-2014, 02:12 PM
While digging through my junk box, I found a couple of servos someone gave me a while back (~10 years ago). I can't seem to find much info on them online though. What I have found is that they are Astrosyn QH4-4276-01. The sticker says that they are 1.8deg/step 2.3V 0.7A. But that is all I have. I found a site online selling some and they have some additional info: 200 Steps/Rev., NEMA 17 frame size, shaft has an easily removed cog belt gear on it. 4 Wire, Has removable mounting plate with rubber washers.

Does anyone else know where I can find some info on these? I emailed Astrosyn, but I am not holding my breath. I am just curious on the torque rating and how to use them. I've never used steppers before, so some things might be universal across all, but I am not sure. I am not sure how to control it or remove the cog (I was hoping they might work for my nativity page turning project).

LightUp
01-01-2014, 08:02 PM
Yes, they are stepper motors. Being 4-wires requires a bipolar driver. I don't know the torques rating.
To control it you need a driver.
Are you planning on a DIY driver or a commercial one?

Search for bipolar stepper drivers and you may find something.
If you are into Arduino stuff then you can use L298 driver, e.g. http://dx.com/p/l298n-stepper-motor-driver-controller-board-for-arduino-120542 to drive your stepper motor.

toozie21
01-02-2014, 10:19 AM
I will probably be using a PIC, but pretty much the same idea. That is a pretty sweet board, thank you for bringing to my attention!

So would your guess be that this can turn a full 360 degrees (I think some only handle 120degrees, or something like that)? Also, there is no way to know where the motor currently is, you just tell it where to go, right?

LightUp
01-02-2014, 11:32 AM
Steppers would turn 360, like an ordinary motor would. Your software has to make it turn clockwise, or counter clockwise, and set the RPM.

toozie21
01-02-2014, 01:17 PM
You know, I just realized something I was ignoring. I was thinking servo, and you were thinking stepper. How can you tell which it is (since both can be 4 wire)?

kingofkya
01-02-2014, 01:24 PM
There is 2 power pins plus a data pin I am not sure why it would have 4 pins unless its non-standard. But normaly servos take just a pwm square wave the length corresponds to the angle the servo should be at.(and it can be driven right off a micro pin:)

If its one of theses you may have issue they use some custom stuff where the servo driver is on the controller board not accely in the servo itself.
http://www.losi.com/Products/Features.aspx?ProdID=LOSB0812

LightUp
01-02-2014, 06:54 PM
...What I have found is that they are Astrosyn QH4-4276-01. The sticker says that they are 1.8deg/step 2.3V 0.7A. But that is all I have. I found a site online selling some and they have some additional info: 200 Steps/Rev., NEMA 17 frame size, shaft has an easily removed cog belt gear on it. 4 Wire, Has removable mounting plate with rubber washers....

For me all the hints were in your provided info: 1.8deg/step, 2.3V @ 0.7A.....NEMA 17 Frame. This sounds soooo much like a stepper motor to me. :)

Edit: I'm not as familiar with RC servo lingo.

kingofkya
01-02-2014, 10:38 PM
Like that? That is most defiantly a stepper.(thats the pic i get with that model you posted)
22330

This however is a servo
22331

toozie21
01-03-2014, 12:30 PM
I agree with you on the stepper now too. Last night I ohmed out the wires and found ~3.4 ohms between pins 1 and 3 as well as between 2 and 4 (with no connection between the two different pairs). That sounds a lot like the bi-polar stepper.

Sadly, I think what I need (to position a rod at a particular location, and not really needing to turn a complete revolution ever) is probably more suited to a servo (if I am understanding what I have been reading/researching). Oh well, I'll have to save these for some future project.

Thanks for the help.

LightUp
01-03-2014, 01:41 PM
From what I recall is that a servo is (usually) a DC motor controlled by an electronic driver. The motor may drive some gears to increase the torque and/or have a mechanical linkage of some sort for linear motion. The motor itself will do more than 360deg, but is limited by the control board.

So, in theory, you still could use your stepper motor but you will end up effectively making your own servo by adding the electronic control and linkages, if linear motion is required. Is that worth doing? I can't answer that for you, since that is a personal choice and may also depend on available materials and tools to get the job done. A 3D printer may come in handy for making the gears. :)

toozie21
01-03-2014, 01:53 PM
I actually was interested in it for radial motion (turning something in a circle), though the second part of my project requires a linear motion. I thought that if i had something in my junk box that kept me from having to buy ALL the pieces for this project, I should try to use it.

What I was lamenting was that I didn't think this stepper would be good at moving to a particular degree point, or am I wrong in that thought?

LightUp
01-03-2014, 02:46 PM
....What I was lamenting was that I didn't think this stepper would be good at moving to a particular degree point, or am I wrong in that thought?

Yes, you are wrong. :)
Stepper motors operate by feeding them pulses, or "steps". Depending on the driver, you feed it 200 steps per revolution (i.e. 1.8 deg per step for your stepper). With micro-stepping, this can be done in even smaller steps, e.g. 2000 steps per revolution (i.e. .18 deg per micro-step).

pmscientist
01-03-2014, 02:58 PM
Moving to a particular point within the step/degree granularity of the motor is exactly what a stepper does. With the stepper you have, you can move to any point on a circular rotation in 1.8 deg increments.

What steppers don't do is provide a reference point on their own. If keeping track of motor position isn't feasible within code, you can accomplish this with an encoder or actuator of some kind. Having at least a known start or stop location would be ideal to allow for a certain amount of unplanned movement due to wind or other force interacting with the display element in a manner not accountable for in code.

toozie21
01-03-2014, 02:59 PM
Yes, you are wrong. :)
Stepper motors operate by feeding them pulses, or "steps". Depending on the driver, you feed it 200 steps per revolution (i.e. 1.8 deg per step for your stepper). With micro-stepping, this can be done in even smaller steps, e.g. 2000 steps per revolution (i.e. .18 deg per micro-step).

My wife would certainly side with you on my regularity of being on the losing side of an argument :).

OK, so if I knew where my stepper was at the time I powered up (or if I had a way to get back to a known "home" position), I could then accurately turn it 23.4 degrees counter clockwise (for example), do something, then turn it 50.4 degrees in a clockwise direction (so 27 degrees past the home position), and continue from there, right?

toozie21
01-03-2014, 03:02 PM
Moving to a particular point within the step/degree granularity of the motor is exactly what a stepper does. With the stepper you have, you can move to any point on a circular rotation in 1.8 deg increments.

What steppers don't do is provide a reference point on their own. If keeping track of motor position isn't feasible within code, you can accomplish this with an encoder or actuator of some kind. Having at least a known start or stop location would be ideal to allow for a certain amount of unplanned movement due to wind or other force interacting with the display element in a manner not accountable for in code.

Sorry, it looks like I hit send before you post came in, so I didn't see it. I think you are right, the stepper is what I want, but I am going to need an encoder or actuator. Is there something easy that people use if all I care about is getting to a starting point?

LightUp
01-03-2014, 05:02 PM
In the CNC world we use a "home" position. Often that is done by turning the motor until a microswitch is activated. This point is the "home" or starting point. A similar scheme is used for "travel limits", that is to determine the beginning or ending of an axis, X, Y, or Z - for example.

In your case it is not clear what kind of means you will use for linear motion, to determine what suitable method we could use to cause a switch to set the home, or limit position. I guess that is a work-in-progress.

LightUp
01-03-2014, 05:08 PM
My wife would certainly side with you on my regularity of being on the losing side of an argument :).

OK, so if I knew where my stepper was at the time I powered up (or if I had a way to get back to a known "home" position), I could then accurately turn it 23.4 degrees counter clockwise (for example), do something, then turn it 50.4 degrees in a clockwise direction (so 27 degrees past the home position), and continue from there, right?

Yes, you are correct on this one. :)

angus40
03-25-2015, 10:41 PM
Have you advanced with this toozie ?

I am thinking of adding a few servo controlled elements .

Steppers are to inefficient and noisy for my liking .

budude
03-25-2015, 10:47 PM
Have you advanced with this toozie ?

I am thinking of adding a few servo controlled elements .

Steppers are to inefficient and noisy for my liking .

I think you mean servos are noisy? Steppers are pretty quiet...

angus40
03-25-2015, 10:56 PM
I think you mean servos are noisy? Steppers are pretty quiet...

No . I mean steppers are noisy :)

You be the judge :)


https://www.youtube.com/watch?v=Z2kAcz-rG5s

angus40
03-25-2015, 10:59 PM
Servo motors are rapidly replacing stepper motors as they last longer , are much quieter and use less energy to run .

The real beauty is the closed loop built in driver models :)

Cheers

budude
03-26-2015, 02:54 AM
No . I mean steppers are noisy :)

You be the judge :)


https://www.youtube.com/watch?v=Z2kAcz-rG5s

Nope - pretty darn quiet - the noise is from the mechanical bits, not the motors - - he even says so. Plus - do a fair comparison - these are big steppers - put those against like servos if you can find them. Try a set of metal gear servo's - they are very loud - way way louder than the steppers in this video... I put mid-lish size metal gear servos in some Halloween skulls - they drown out the speakers I put in them when they "talk".

angus40
03-26-2015, 06:38 AM
Ah , I guess on a smaller scale for your purpose steppers may be quieter .

If using metal gear servo motors I would suggest a helical worm gear design .

A Spur gear design will be noisy , depending on # of teeth >pitch > pressure angle with/without reduction gears etc. and a host of other variables

LightUp
03-26-2015, 08:30 AM
Nope - pretty darn quiet - the noise is from the mechanical bits, not the motors - - he even says so. Plus - do a fair comparison - these are big steppers - put those against like servos if you can find them... .
He demonstrated a DC servo, NOT a stepper - he even says so. :)

LightUp
03-26-2015, 10:02 AM
Have you advanced with this toozie ?

I am thinking of adding a few servo controlled elements .

Steppers are to inefficient and noisy for my liking .
The DC servos shown in the video are not cheap, starting at $254 each. Source: http://www.motionsolutions.com/store/pc/Teknic-Clearpath-MC-Series-c752.htm

toozie21
03-26-2015, 11:31 AM
Have you advanced with this toozie ?

I am thinking of adding a few servo controlled elements .

Steppers are to inefficient and noisy for my liking .
I didn't complete it in time for Christmas, so I shelved it until this year. Now I am putzting around with it whenever I get a few free minutes (I have a toddler and a 6 week old, so very few free minutes). I ended up going with servos from allelctronics.com . I have 5 of them that are going to turn the cover and 4 pages (the 5th page stays static) via a PIC microcontroller. The display is build, the servos are mounted, next I need to dust off my code from last year and fine-tune the starting/stopping points for each page.

budude
03-26-2015, 12:45 PM
He demonstrated a DC servo, NOT a stepper - he even says so. :)

OK - you got me there - I did not actually listen to the whole thing - I assumed these were steppers since the comparison was how loud steppers are... Anyway - still contend for at least regular hobby grade stuff that servo motors make more noise than stepper motors...

angus40
03-26-2015, 02:17 PM
I didn't complete it in time for Christmas, so I shelved it until this year. Now I am putzting around with it whenever I get a few free minutes (I have a toddler and a 6 week old, so very few free minutes). I ended up going with servos from allelctronics.com . I have 5 of them that are going to turn the cover and 4 pages (the 5th page stays static) via a PIC microcontroller. The display is build, the servos are mounted, next I need to dust off my code from last year and fine-tune the starting/stopping points for each page.

Sorry my post went off topic here Toozie .

I am looking forward to seeing your pic based project in action once you find the time and maybe motivation .

I hear you about not completing projects in time, :)

I am starting to pile up a few incomplete projects myself .

toozie21
03-26-2015, 02:44 PM
Sorry my post went off topic here Toozie .

I am looking forward to seeing your pic based project in action once you find the time and maybe motivation .

I hear you about not completing projects in time, :)

I am starting to pile up a few incomplete projects myself .
Ha ha ha, no worries, this topic was pretty much dead, so fine by me (and I've tangented plenty of topics on my own).

The pages are printed up on coro and are 18" tall by 12" wide. Should be pretty neat if I can get it done. I think I am pretty close, I just need some time to work on it. To make my life easier, it will be controlled via serial commands into the PIC. I am doing it this way since it is "synced" to my animated blowmold nativity running off a PIC. I'll just have that PIC send out status updates as it changes which figures are lit up, and then that will keep the book in sync.

Sort of tying into the tangent, I have a feeling these servos will be slightly noisy. Not terrible since they are outside, but if you ever see some of the 3-axis skulls (and other things like that) that use servos, the videos of them are usually covered in the chatter from them moving around.

Technician
03-26-2015, 02:45 PM
Consumer grade RC servos are noisy because of the noisy mechanical geartrain. To get high power (speed and torque) into a small package, high speed motors with gears is used. Gearless servo's are all around you. Most common ones are in your hard drive to position the heads and drive the heads in an inkjet printer.
Stepper motors are no longer used in modern hard drives. A fair comparison for noise would be a hard drive seeking tracks vs a floppy reading tracks. Floppies still use steppers. Another real world use is your ink jet printer. Dot matrix printers used stepper motors. Flat bed scanners use steppers. Look inside a modern ink jet printer. Behind the carriage is an optical encoder strip. Steppers don't use one.
Note the difference between a flatbed scanner and an inkjet printer.

FYI, there are AC varieties of servo motors too. PM 3 phase aka brushless, and 2 phase induction AC motors.

With noisy gears removed, the motor noise can be compared.

Shockwave
03-26-2015, 04:26 PM
Let me just point out that pololu robotics has DMX to servo controllers very cheap. One board can drive lots of services, making it great for animatronic.