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Posted (edited)

This is the servo motor I have on my 3200 and I believe it is the same as the one on the 4500 as well. I have running at around 60 stitches a minute maximum but to get there I just barely nudge the pot from it's zero position, I would like to get more control over the lower end of the range but the pot is way to sensitive and just a touch makes a huge difference in speed.

I have not seen the schematic of the motor but it sure seems the pot is wrong for this application. Has anyone replaced the pot on their servo? It seems that the pot is probably linear and should possibly be a log type pot.

Here is the motor:

servo_motor_for_sewing_machines.jpg

Thanks!

Bob

Edited by BDAZ
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Posted

My FS-550 motor has a multi-position rotary switch. I wish it could be converted to a log taper pot. Let me know if/how any mods work out for you.

Posted IMHO, by Wiz

My current crop of sewing machines:

Cowboy CB4500, Singer 107w3, Singer 139w109, Singer 168G101, Singer 29k71, Singer 31-15, Singer 111w103, Singer 211G156, Adler 30-7 on power stand, Techsew 2700, Fortuna power skiver and a Pfaff 4 thread 2 needle serger.

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Posted

THis shouldn't be rocket science. I spoke to Bob the younger, and they are not aware that there is an issue. I'll oopen it up when I have cleared my back log..Any chance of getting hold of a schematic?

Cya!

Bob

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Posted

One big difference I see is that your motor has a large pulley. Mine has a 50mm (2") pulley, which gives more low speed torque and runability.

Posted IMHO, by Wiz

My current crop of sewing machines:

Cowboy CB4500, Singer 107w3, Singer 139w109, Singer 168G101, Singer 29k71, Singer 31-15, Singer 111w103, Singer 211G156, Adler 30-7 on power stand, Techsew 2700, Fortuna power skiver and a Pfaff 4 thread 2 needle serger.

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Posted

Aside from the pulley difference, when I opened up my motor, I looked at the switch and found that it is populated with small resistors. I'm not into electronics anymore (for 3 decades) and have no meters. But, I'm guessing that someone with the right equipment and good close-up eyesight could figure out how to replace the rotary switch with a suitable military grade, long life, log taper pot (or stacked concentric pots).

Posted IMHO, by Wiz

My current crop of sewing machines:

Cowboy CB4500, Singer 107w3, Singer 139w109, Singer 168G101, Singer 29k71, Singer 31-15, Singer 111w103, Singer 211G156, Adler 30-7 on power stand, Techsew 2700, Fortuna power skiver and a Pfaff 4 thread 2 needle serger.

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Posted

The pic s not my machine but one off the net. I assume I also have a 2" pulley. I'll try to take a look this afternoon.

Cya!

Bob

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Posted (edited)

Found the problem! The pot is a 220K Ohm linear pot. The machine is off when there is zero resistance. When I crank it to the maximum that I would eve use, it's around 80K ohms. So that's the answer! Replace the 220K ohm pot with a $.99 log taper (for testing) 100K. If I get the range and speed curve I am interested in, I'll invest in a better pot. The pot is plugged into the board using a standard Molex connector, so one could conceivably have a 20K 60K and 100K and simply plug and play.

I have ordered a couple of pots and will install them when they arrive.

I have just ordered the pots and connectors and I'll give it a shot.

Cya!

Bob

Edited by BDAZ
Posted

I have the same motor on a 3200 and it has a full range of speed, using about 3/4 of the adjustment on the dial to go from 0 to as fast as I want to go, but the control isn't overly sensitive.

Chief

"Life's too short to carry ugly leather"

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Posted

I'm not concerned about going fast. I want to max out at 60 spm and have the full range of the pot cover 0 to 60 ONLY.

Thanks!

Bob

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Posted (edited)

Just noticed this thread or I would have responded a lot sooner. I ordered a Servo from Toledo (Ordering and shipping was fast and flawless.) I discovered that low end speeds were almost impossible to get right. I am a DIY sort and since it was 10pm I didn't expect Toledo to be open. I grabbed an old dead computer gaming headset and ripped the volume control off of it (2K Ohm) and grabbed a pot from a computer Power supply fan (100k ohm). Spliced them in series and was able get the speed adjusted to my liking.

For ~60 SPM the reading is 18.3K Ohms and using the 2k Pot will adjust the speed up words to ~120 SPM. Its's no wonder everyone is having trouble getting it zeroed in at the right speed since at the low end a turn of just 3 degrees can result in a doubling of speed.

The other advantage with doing this mod is that I now have the speed control mounted near the reverse lever so I can quickly and easily adjust the speed.

I didn't even know there was an item called a Log/audio Pot, and apparently neither did the person who designed this :( Bob seems to be right on the money and if his test works as well as I expect it to I will grab a Log Pot and throw it in series.

Thanks for the info Bob.

Random

Edited by Random

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