Cowboy Analog Servo Motor Modifications?

[Trox]

Constabulary,

Here is an other one I use on my skiving machine. (on the wall, laying on the top of the machine is a bigger controller not in use)

I run this on full speed all the time, its for the bell knife motor only. It has a little 220 v servo motor for the feed wheel that goes direct in single phase outlet.

Actually this machine has three electric motors; one for the knife (380v- 3 Ph), one for the feed wheel (220v- single Ph with a pedal for the speed) and one for the exhaust (220v -single Ph). So I connected the two single direct to the outlet and run the Freq. converter on the bell knife motor (on full speed 50 hertz all the time).

These controllers regulate frequency on your AC motor; 50 hertz are full speed. If you give it 25 hertz it runs on half speed and so on. (all clutch motors are AC motors, and all AC motors are originally 3 Ph. Some are rewired into single Ph motors)

A normal 3 Ph sewing machine clutch motor is much simpler to hook up than this one.

When you look for a controller for your clutch motor find one that can handle a bit more than your motors Watt and Amp ratings. You find than info on the motor sign.

Good luck

Sorry for the off topic.

Tor

[Constabulary]

I will keep that in mind - but I will try a servo motor + speed reducer first as I don´t like the idea of a permanently running clutch motor.

But always good to see how others have solved their motor problems. Thumbs up!

[BDAZ]

I finally received my 100K log pots from China. The connectors arrived a week ago. I soldered the connector leads to the pot, plugged it into the board, reassembled the motor cover I was done. There was a noticeable improvement. The slow speed selection has much greater range than before. I would say 3 times the movement of the knob from just starting to move to around 1 stitch per second. Not a great as I had hoped BUT it will still reach stitching speeds higher than I will ever need.

Next I will try lower resistance pots to increase the range. There is a threshold of minimum resistance when nothing happens. I am not sure if that is adjustable, but the new pot has to be turned a bit before the motor kicks in.

In summary, well worth the couple of bucks spent and the few minutes involved but I suspect the lower value pots will bring a bigger improvement in low speed control.

I will be trying the magnet mod once I finalize the replacement pot.

Cya!

Bob

Edited June 8, 2014 by BDAZ

[Random]

I did mine last week with the 100K Pot and a 50K pot. I adjusted the 100K Pot to just below the thresh hold where the motor started (12K ohm) and then used the 50k pot for fine control. Substituting a 10K or so resistor for the 100k pot would do the same thing. I also modified the magnet positioning as was also suggested and I now have fantastic control.

[Wizcrafts]

I finally received my 100K log pots from China. The connectors arrived a week ago. I soldered the connector leads to the pot, plugged it into the board, reassembled the motor cover I was done. There was a noticeable improvement. The slow speed selection has much greater range than before. I would say 3 times the movement of the knob from just starting to move to around 1 stitch per second. Not a great as I had hoped BUT it will still reach stitching speeds higher than I will ever need.

Next I will try lower resistance pots to increase the range. There is a threshold of minimum resistance when nothing happens. I am not sure if that is adjustable, but the new pot has to be turned a bit before the motor kicks in.

In summary, well worth the couple of bucks spent and the few minutes involved but I suspect the lower value pots will bring a bigger improvement in low speed control.

I will be trying the magnet mod once I finalize the replacement pot.

Cya!

Bob

Bob;

Are these mods for the Family Sew FS-550 motors? What is the mod to the magnets?

Re the 100k pot. Is it a 10% center, log taper clockwise, carbon pot?

Edited June 8, 2014 by Wizcrafts

[BDAZ]

Yup, Mod is for the FS-550. No specs on the pot other than log taper, carbon and counter clockwise. It's a drop in replacement for the supplied pot. I have ordered a 50K and 20K pot and will try both. I may even extend the jumpers and have the pot mounted on the table for easier access,

The magnet mod is described earlier in this thread.

Cya!

Bob

[BDAZ]

I did mine last week with the 100K Pot and a 50K pot. I adjusted the 100K Pot to just below the thresh hold where the motor started (12K ohm) and then used the 50k pot for fine control. Substituting a 10K or so resistor for the 100k pot would do the same thing. I also modified the magnet positioning as was also suggested and I now have fantastic control.

I was wondering what the threshold was set for. A 10K resistor in series with the pot should do the trick! Any issues with the magnet mod?

Cya!

Bob

[Wizcrafts]

My FS-550s has a rotary switch, not a pot. The slowest setting is full clockwise. It speeds up the wrong way, CCW. On the pot mod, is the slowest speed at the lowest resistance (~10 - 12k)?

[JoMama]

I did the magnet mod above on a Family 550 servo, but the motor is the same as this Cowboy motor with a slightly different electronics box. Running a 2" pulley on the motor, a 3:1 speed reducer and setting the rotary speed limit switch to around 3000 rpm. I get easy control from 15 spm to around 400 spm. I also put an extension on the control arm coming off the motor (not shown in the pictures posted earlier) and moved the bottom control rod attachment point from the piece that bolts to the top edge of the pedal, down to the side of the pedal, after drilling a hole in the side of the pedal. You don't need the arm extension if you drill the hole in the side of the pedal closer to the pedal pivot.

Now, there is no reason to set the speed limit lower, because the foot pedal has much more range, for better control. It uses the full range of the foot pedal now.

[Random]

My FS-550s has a rotary switch, not a pot. The slowest setting is full clockwise. It speeds up the wrong way, CCW. On the pot mod, is the slowest speed at the lowest resistance (~10 - 12k)?

Thats right. the first ~10K ohms is a dead area and my servo does not activate until past that point. As the resistance increases the speed increases. The Pot I used from Frys electronics is labeled as a "16mm Potentiometer 50K Ohm audio taper without switch combo terminal" by Philmore.

I was wondering what the threshold was set for. A 10K resistor in series with the pot should do the trick! Any issues with the magnet mod?

Cya!

Bob

The Magnetic mod suggested by JoMama in post #12 was spot on and I had no real problems. His directions are great. Just make sure to pay attention to the clocking (1/4" grooves at end of shaft that he mentions in step #10 for easy alignment. Se hi res diagram below :-)

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Edited June 9, 2014 by Random

[catskin]

I was thinking of ordering a servo motor from Toledo but after reading all of this thread I am wondering if it is possible to get a servo that works without all this pot and mod and ohm crap done. The cowboy 4500 I bought a couple years ago has a servo that with the nob turned to the slowest speed will go so slow you can almost have coffee between stiches, are these good ones no longer available? I notice the Bob,s have not said anything on this thread I wonder why if they sell these motors?

[BDAZ]

I assume that they buy standard industrial sewing machine motors and I would guess for every leather machine sold, there are dozens of industrial machines sold for the garment industry and similar high speed stitching. As to ordering the motor, this IS the motor from the 4500.

I had no problem getting the machine to stitch slowly but I wanted to be able to get more of a range in the slow end but the option to gradually increase the speed when I have less complicated items to stitch. With the existing potentiometer, that was not possible, Just a touch and it was slow then another touch and it was fast. The two mods go a long way in optimizing the machine for slow stitching.

While the magnet mod is a bit more work and a bit finicky, the pot mod is plug and play. When I finalize the values I'd be happy to make a plug and play mod available for a few bucks. The pot mod should take less than ten minutes.

Cya!

Bob

[Wizcrafts]

To your knowledge, will your pot mod substitute for the rotary switch currently installed in my FS-550s? I already have great slow speed control, especially with the 3:1 reducer in the chain.

[BDAZ]

I assume your switch is like this one with a number of resistors switched instead of a carbon /wiper or wound /wiper

system?

There should be some marking on the pot giving it's value. The stock pot on my 3200 was 200K. I think we have determined that the ideal pot would have an initial resistance of 10 ohms and then max out at around 50-100 ohms.for typical leather stitching. This should give you the full (around 340 degrees) range of the pot to control the maximum speed.

The switched resistors that you have is a much more expensive potentiometer because each detente will give you a very accurate resistance and should be easily repeatable and could be calibrated. BUT if the behavior of the switch is too abrupt, going from slow to maximum, then a lower value pot would be called for.

I just ordered a 50 ohm and a 20 ohm pot and will jumper a 10 ohm resistor so there wound be any significant dead space on pot and it will be in the best part of the curve.

Cya!

Bob

[CowboyBob]

Catskin,

Yes,you have the same motor.We have always felt they worked pretty good esp when connected to a speed reducer,but I guess it's like anything you buy some people need it to be different.Look what they do to a new car or truck,jack it up big tires,loud exhausts.paint,sunroofs & etc.

It has been some very interesting reading & way over my head since I'm not into electronics to understand it all.

This motor is 1000x better than the one we used to sell that you had to program for the speed,it went from 0-wide open in 1/2" of foot pedal push.

[BDAZ]

Bob, I would liken this to adding a better sound system or maybe a GPS to a new car. It's not about looking different but about optimizing the performance of the motor for low speed operation. Once we determine what the optimum value for the potentiometer is, you could request the motor with a potentiometer (The speed control knob) with the appropriate value for leather work. The correct value should allow the speed control to go from minimum to maximum (the fastest speed a leather worker would want) with the complete turn of the dial. On my new 3200, from newbie slow to a controllable speed for belts was about 10% of the dial.

The magnet mod is a bit more problematic and would take some retooling for the manufacturer but the change in values on the speed control is a no cost , no brainer.

Cya!

Bob.

[JoMama]

To your knowledge, will your pot mod substitute for the rotary switch currently installed in my FS-550s? I already have great slow speed control, especially with the 3:1 reducer in the chain.

With a 3:1 reducer, I still use the stock multi-position switch and just leave it set a couple clicks below the fastest speed. Before the magnet mod and rod repositioning on the pedal, the motor would go from zero to full speed using only 10-15% in the middle of the pedal range. After the mods, the first 10% of the pedal movement is dead-band (intentional) and the last 90% is variable. When I say pedal range, I mean hard-stop to hard-stop on the pedal, as if the control rod was disconnected, not the stops on the motor arm limiting the pedal movement. I'm typically only doing 30-90 spm, but when I want to go faster (300+), I don't have to turn the knob to a faster setting, I just floor it, because the control is soooo much better.

I see no reason to change my switch for a lower resistance pot.

[BDAZ]

JoMamma, My motor has a 220K pot and not the multi resistor switch. Do you know what the value of yours is? It may be a lower value than mine?

Thanks!

Bob

[pcox]

I have 5 machines with the motors Bob sells and have installed many more with no control problems. If what you are after is more pedal travel, that is a function of the ratio between the point of connection of the rod or chain on the servo motor lever and the foot pedal. closer to the pivot on the foot pedal/longest point or even extend the lever on the servo will give you more pedal travel/less sensitivity. All of my leather stitchers have speed reducers.

Edited June 10, 2014 by pcox

[BDAZ]

This is about more accurate maximum speed control.

CYa!
Bob

[JoMama]

JoMamma, My motor has a 220K pot and not the multi resistor switch. Do you know what the value of yours is? It may be a lower value than mine?

Thanks!

Bob

I never checked it, since I did not see the speed LIMIT as the problem. The issue I had was a lack of range of motion on the motor control arm between zero and full speed. When I was first looking at it, I noticed that adjusting the speed slower, just increased the dead-band before the motor started to spin and did nothing to increase the arm's range of motion from zero to full speed. This motor controller does not adjust the travel range when you when you adjust the pot as you would hope. My guess is that the pot just provides an offset voltage to suppress the voltage from the linear hall sensor, limiting the speed by decreasing the effective output of the hall. Hench the decreasing resistance on the pot to limit the speed.

I have used the same linear hall sensors in numerous other applications, and typically, you want the magnet to approach the sensor axially to its face, so the magnetic field extending from the face of the magnet gradually presents to the sensor. On this motor setup, the magnet approaches laterally, where the magnetic field lines are closer together and the transition from zero to full field strength happens with a shorter motion and is less linear.

I have my FS-550 motor RPM set at 2830 RPM (two clicks below the fastest speed, 3450rpm) and it is easy to control the speed between 15 and 60 stitch/min, but it will also spin up to 300+ when I want it to, also totally controllable.

I'd suggest you go back to the stock pot, set it between 75% and 100%, do the magnet mod, drill a line of holes in the side of your pedal and attach your pedal rod or chain to those, to see which position you like the best. The closer to the pivot you attach the rod or chain, the better your control will be. That can also limit the speed by not having the pedal movement that allows the motor control arm to travel into the faster region.

edit: As pcox mentioned, you could increase the controllability by just moving the rod or chain closer to the pedal pivot, but the magnet mod changes the speed curve to have more linear speed control.

Edited June 10, 2014 by JoMama

[BDAZ]

First off I have already done the pot mod and replaced it with a 100K pot. I generally work on intricate pieces with some straight sewing and I like to work at 30 SPM for the intricate stuff and 80 SPM for straight line stitching, no faster. I want to be able to set my maximum speed for a piece leave it there, consequently the pedal is less important to me than the speed setting. Prior to the mod, only a fraction of a turn would take me from 0 to 80. Now it's half a revolution of the knob and the speed increase is gradual and repeatable.

I have done the magnet mod and I suspect it may be problematic, reducing the amount of travel that triggers the transducer. Maybe my magnet is angled a bit too much but it ts definitely an improvement and could be incorporated in the manufacture of the arm, with a longer angled or tapered magnet since the transducer works on the strength of the flux.

Cya!

Bob

[JoMama]

Just a note on the magnetic field, the strength of the field is an inverse cube relation to distance. By biasing the voltage from the hall sensor with the pot/switch to limit speed, you miss out on the long gradual taper of the sensors voltage curve, which improves the slow speed control, while still leaving plenty of top speed.

Now if you are setting a speed limit and then running the machine at that limit for a bunch of pieces, that's completely different from what I'm looking for, which is to easy slow speed control via the pedal along the curves and tight corners and then still be able to open it up on the straights without stopping to adjust a dial. My speed limit is my foot.

Cheers,

Jo

[catskin]

Thanks all for your input. I am NOT an electronics person 99% of this stuff goes right over my head, but now I sort of understand what you are all getting at.

[BDAZ]

I just received my 20K pot and wired it in series with a 100K pot and discovered that my threshold resistance (The minimum amount of resistance in the circuit that is required to start the motor) is 14 ohms. I think that a 100K Log pot with a 10K resistor in series is just what the doctor ordered. The 10K will allow the pot to kick in at the ideal part of the log curve for a gradual speed increase.

I have extended the jumper to an identical jumper mounted on the back of the motor housing so I can test various components without removing the motor housing.

Cya!

Bob