Getting Control Of Your Servo

[Evo160K]

Last year after picking up a couple of old machines to restore, I decided to try sewing.  Of course, I immediately ran into the problem of controlling the clutch motor on the Singer 45K25 and the CS-1000 3/4 HP servo motor on the Singer 45K53.

 

Well I was just about at my wits end trying to control those motors when I stumbled onto the LW post by DDahl that led me to search the internet further and eventually to the two links and videos below that explain how to modify a servo controller.  Apparently servos are all pretty much generic in their design.  The first link is the same modification member Trox tried and mentioned in one of his posts, and the same one member J Hayes tried and liked.  The second link shows a refinement of the method in the first link.

 

A number of people must have seen the first video, but apparently not tried it, because people are still asking about slowing down servos.  They must have felt like I did when I first read it and watched the videos.  I thought no way can I do that..........I hate electricity that “black art”, but after several more viewings and a look inside at the controller, I realized the modification is really quite simple.  Anyone who can use a pencil, an eraser, a scissors and a screwdriver can do it.  I’ll bet our middle school kids and grandkids can do it.......maybe younger.

                                                                           

The theory is, the more light the electric sensor eye sees, the slower the machine runs; conversely, the less light the electric eye sees, the faster the machine runs.  So the idea is to modify the paper card that blocks the light ray the eye sees, so you get the control you want.  The video in that second link shows just how much control you can get.......it really works amazingly well.  Read and watch everything a couple of times, it’ll make good sense, particularly once you look inside the controller.

 

The next thing I learned, is the slower the start speed rpm is set with the up/down buttons, the greater the torque you get, so set your start speed to "0" or what ever is the slowest, if your machine has that option.......maybe experiment with the start speed setting.  Once you realize what’s going on, you can fine tune your start speed and top speed to anything you want......no more start slow with no torque, then “Oh S—t” like member JimC said.

 

Another plus is, it doesn’t cost a dime to do.

 

http://www.swflholsters.com/358/sewing-servo-motor-diy-smoother-speed-control-mod-paper-gradient/

 

https://www.youtube.com/watch?v=wu2OT9MtzMc&feature=youtu.be

 

I made a short video with the wife’s iphone showing my K53 with 50 mm pulley, speed reducer, 277 BP thread, 24 leather point needle and two pieces of 14 oz. veg tan (28 oz.), but wouldn’t you know, I’m having trouble uploading it.  I promise it shows the machine starting at one stitch every two seconds and gradually increasing like in the video in the second link above.

Edited November 4, 2016 by Evo160K

[Gregg From Keystone Sewing]

That's GREAT, I've tried this a few times on my own without any success.  After viewing this, I'll definitely try again.  

[CowboyBob]

I've tried doing this too & gave up using this motor on machines where I know people will want to go slow,we use the SL-550 instead & get the slow speed w/o any work.

[Wizcrafts]

I obtained a printed out gradient from Cobra Steve and installed it in a push button servo motor I have. It definitely improves the slow speed controllability of an otherwise touchy motor. But, and this may be my fault, there is a momentary dead spot in the travel, as I increase the speed. Maybe I didn't tape the gradient on 100% perfectly. It passes quickly. I would recommend trying this if you have a touchy servo motor.

In the end, I bought a Family Sew servo motor from Toledo Industrial Sewing Machines. It starts rotating at an almost immeasurable rate and has a very smooth transition to whatever maximum speed I set on the dial. I relegated the gradient modified motor to another less critical machine.

[TinkerTailor]

I have to add that i have the non needle position techsew motor, and while it does not have the knob speed control, once I played with the settings and got the right size belt for the small pulley on my speed reducer, I have smooth control from 1 stitch every 2 all the way to probably 200-300/min. This is more than fast enough for my work, and no need for the knob. For some strange reason my 5100 came with the belt fitted to the middle pulley on the reducer, and I found the speed was notchy when it got slow, presumably because the motor didn't have enough rpm. No lack of punch, just lack of smooth speed control. I am pretty sure that this motor could turn this machine at its top speed on the smallest reducer pulley if I set it that way, so there is no need for the extra speed of the middle pulley.  Besides, a 441 at 900 stitches a minute is a scary thing to behold........If you set it to 3 stitches per inch, that is 25 feet per minute or just over 1/4 mile an hour.......Yeehaw..... Other than the belt thing, i have no complaints with this motor. If I am doing detailed work and I want to limit the top speed for safety, I put a 2x4 under the pedal....

Edited November 4, 2016 by TinkerTailor

[SARK9]

I've had quite a few of the older Consew CM-1000 servo motors....still have 4 of them in the room, plus two different examples of the newer "CSM-1000" variety.

On the optical speed controllers, I've had better results using a solid black, 100% opaque cam/vane rather than the gradient....its difficult to consistently ramp the response with most of the gradient media I've tried. I settled on a little piece of very dense but thin black cardboard from a flashlight box I had...and I use a sort of crescent shape to progressively subtend the light beam as it rotates. Its very easy to reposition and adjust...I stick the new vane to the original blunt foot with a bit of the Sail-rite double sided tape and do some trial and error with it out on the bench. None of them I've modded have needed any further attention for years, and they work very well.

The hall effect controls on the newer CSM-1000 models are a bit too abrupt for my taste when they hit their *on threshold* and I don't care for them as much, but I use the two I have on higher speed fabric machines (without reducers), both programmed for their max RPM. Maybe one of the electronics folks will dive off into one eventually and teach them some manners, as the separate components make it possible to do some *very different* mounting configurations with them.

-DC

Forgot to add the swflholsters video was my original inspiration to start playing with the shapes.

Edited November 4, 2016 by SARK9

[Evo160K]

Hopefully there's a video here now.  I believe you'll need to download it to play it.  My apologies for it being upside-down.  If someone could correct it all and re-post it, that would be great.

It shows how much low end control and punch you can get with the modification while still having full control as the speed increases.  I made a card from a manila, file folder and cut a small segment in the center of the leading edge (like in red below) about the same diameter as the beam.  It's similar to sketch #3 shown at 6:27 of the video in the second link.  I also used a pencil to tailor the speeds to my liking.  I could have increased top speed by making the trailing end of the card darker, but saw no need.

https://www.icloud.com/attachment/?u=https%3A%2F%2Fcvws.icloud-content.com%2FB%2FAdOVj50mTxcKiXLxatmavInIZaCyAXOXjq4_y0CyfxT5zXjEpsItW3AY%2F%24{f}%3Fo%3DArQQDesgQCQ_vkQiXfnmOjjC2xxXRVc55LFzgrR4mVgw%26v%3D1%26x%3D3%26a%3DBbUeQCmI4LKBAzuXNwEA_wHIAP8E4CEC%26e%3D1480895672%26k%3D%24{uk}%26fl%3D%26r%3DD3465993-54E5-4A2D-B959-6768C7D74067-1%26ckc%3Dcom.apple.largeattachment%26ckz%3D9FABDD43-F4CD-4AB1-B195-92D284A1EB74%26p%3D53%26s%3DRzt6gAXB3n86lgfio0BH9vUfyww&uk=gq-hM38k-kV2NQWIe-TMCA&f=IMG_4535.MOV&sz=92358274

[dikman]

" Apparently servos are all pretty much generic in their design." While this is generally a true statement, design does change, for example the optical operation you refer to appears to be an "older" design and they are using a different design now where the optical gradient isn't used. None of my three units has it, and it seems that once one changes the design the other makers follow suit.

The best thing with a servo is to experiment with the start speed and top speed settings and in my case they appear to be interactive to some extent. Also, if you want to maximize the torque at low speed then fitting a speed reducer as well is highly recommended.

[Constabulary]

my JACK servos have a magnetic accelerator unit. You can tweak them a little bit but I only needed a hex keys to move the magnet lever a bit back. Agree - adding a speed reducer is the best you can do.

[Evo160K]

On Friday, November 04, 2016 at 9:45 AM, Wizcrafts said:

there is a momentary dead spot in the travel, as I increase the speed. Maybe I didn't tape the gradient on 100% perfectly. It passes quickly. I would recommend trying this if you have a touchy servo motor.

 

Wiz.

If you want to try to smooth out that dead spot, you might take the cover off and note exactly where the gradient is when you get the hesitation.  Some part of that area under the light beam, I believe it's the trailing part, needs to be darker, maybe a couple more pencil lines.  Dare say, you might even be able to hold a pencil lead or small nail or something similar there first to block light to see where it speeds up, that will pinpoint exactly where you want to make lines to darken the gradient.  The darker you make the gradient (less light getting through to the eye), the faster the motor runs.  You can go darker or lighter to tailor the ramp up to your liking.

Although the gradient is about an inch wide, as far as I can tell, it's only the portion that passes under the light beam from dead stop to top speed that concerns us.  It may take a bit of marking and erasing, but you'll get it smoothed out for sure.  It's not rocket science like I first thought.

[Wizcrafts]

9 hours ago, Evo160K said:

Wiz.

If you want to try to smooth out that dead spot, you might take the cover off and note exactly where the gradient is when you get the hesitation.  Some part of that area under the light beam, I believe it's the trailing part, needs to be darker, maybe a couple more pencil lines.  Dare say, you might even be able to hold a pencil lead or small nail or something similar there first to block light to see where it speeds up, that will pinpoint exactly where you want to make lines to darken the gradient.  The darker you make the gradient (less light getting through to the eye), the faster the motor runs.  You can go darker or lighter to tailor the ramp up to your liking.

Although the gradient is about an inch wide, as far as I can tell, it's only the portion that passes under the light beam from dead stop to top speed that concerns us.  It may take a bit of marking and erasing, but you'll get it smoothed out for sure.  It's not rocket science like I first thought.

Thanks for that suggestion. If I ever decide to remove the commercially produced gradient and make my own, I will use lead pencil strokes. The one I have in there was pre-printed on thin plastic for Leather Machine Company and offered to their customers.

[Evo160K]

You're welcome, Wiz.

Btw, I would keep the gradient from Leather Machine Company, it's working well, I would just darken it at the dead spot.