What Exactly Is An "eps" (Electronic Positioning System)?

[George1520]

On 4/14/2019 at 8:20 AM, turbotexas said:

Would one of these work on a Singer 31-15 and a 153w103?

it will not work on any machines that have the stich length knob at the back of the flywheel. Singer w 111 type machine. I purchase one that has the sensor installed. The way they did it they machined the flywheel flat  and tap 3 screw holes for the sensor. Before they install it they cut the stich regulator and shoved in the hole. Basically  the machine is set to only one stich length 

[Matt S]

In theory a 1-signal NPS could be replaced with a microswitch or IR notch sensor positioned to trigger at the apex of the take-up lever.

[George1520]

On 10/6/2019 at 4:01 PM, Matt S said:

In theory a 1-signal NPS could be replaced with a microswitch or IR notch sensor positioned to trigger at the apex of the take-up lever.

It is basically a simpler version of the computer mouse. An optical switch that outputs twice for one flywheel rotation. One for the needle up and one for needle down.  If you replace it with micro switches you will need two. Otherwise it will work every other time, at least in theory.

[Matt S]

36 minutes ago, George1520 said:

It is basically a simpler version of the computer mouse. An optical switch that outputs twice for one flywheel rotation. One for the needle up and one for needle down.  If you replace it with micro switches you will need two. Otherwise it will work every other time, at least in theory.

Not all NPS sensors are the same. I'm sure that some have an optical rotary encoder but I've taken apart several low-end NPS units and found them to be a hall-effect sensor with a small magnet on the rotor wheel. Essentially all they do is provide a logic signal when the magnet passes (hi or lo depending on the brand). Easily replicated with many different off-the-shelf sensors.

I suspect that Jack servos count the number of motor revolutions between NPS signals, then divides by two to extrapolate for the "other" position. The ESDA servo I have doesn't do this, and have terrible granularity on the throttle.

[FDC]

I added one on my Techsew 5100 as a Chinese import (shame) EPS was cheap cheap. You have to adjust your servo settings and there’s not a lot of readily available info out there but you can do it. Was it worth it on a slow machine like mine? Sometimes. Would I recommend it to someone else? Acquiring knowledge costs money and time, in this case the knowledge came at a reasonable price so yeah, try it. 

[Bikersmurf]

Does your servo motor go to needle up if you push down with your heal on the control pedal? I had to adjust lengthen the linkage slightly to allow the control pushed up to allow this. 

[CowBoyOUTLAW]

On 10/9/2019 at 12:04 AM, Matt S said:

Not all NPS sensors are the same. I'm sure that some have an optical rotary encoder but I've taken apart several low-end NPS units and found them to be a hall-effect sensor with a small magnet on the rotor wheel. Essentially all they do is provide a logic signal when the magnet passes (hi or lo depending on the brand). Easily replicated with many different off-the-shelf sensors.

I suspect that Jack servos count the number of motor revolutions between NPS signals, then divides by two to extrapolate for the "other" position. The ESDA servo I have doesn't do this, and have terrible granularity on the throttle.

You are right, most Energy Saving Servo Motors use hall-effect sensor, instead of photoelectric sensor. Except regular needle positioner synchronizer, JOG Dial (Electronical needle positioning) is new method to adjust the needle position, see below video.