What would your ultimate needle positioner/synchroniser do.

[beefy]

In keeping with my growing love of my newly acquired industrial sewing machines, I'm now getting myself absorbed in designing an electronic circuit and programming a microcontroller to make my own needle positioner.

I've given up trying to get any sensible instructions for my cheap Chinese servo from the seller. I know it also doesn't have any heel press functionality.

So far this is the functionality I'm programming for it:

1. Single revolution/stitch from EITHER the needle UP position or needle DOWN position.
   This is done by a quick tap on the pedal, either forward (for needle DOWN) or heel tap (needle UP).
2. Stop in needle DOWN position when foot pedal released.
3. Go to needle UP position when heel tapped.
4. Adjustable "coasting" speed when searching for either needle UP or needle down position. This is to have control over overshoot if servo cannot stop motor fast enough.
5. Search for needle position is cancelled if operator presses foot pedal while motor is coasting and waiting for needle UP or DOWN signal.
6. Safety feature - adjustable timeout for motor coasting and looking for needle UP or DOWN position. Coasting stops if signal not received within timeframe.
   This prevents the machine going on forever if some fault occurs like a broken wire, or faulty needle positioner.

Are there any other useful features a needle positioner could have ?

Edited 16 hours ago by beefy

[fibersport]

Get yourself a Kinedyne needle synchronizer for accuracy but I'm pretty sure the servo motor controller is what really controls the functions, the synchronizer is just a switch to indicate where the timing of the machine is.  The Kinedyne is an optical synchronizer and is super accurate.  http://kinedyne-motor.com/products/HM-750SH/234.html You could just get the Kinedyne motor and synchronizer and be done with it.  Just sayin -

Talk to Ryna at http://www.neelsaddlery.com/ 

I have no affiliation with Kinedyne or Neels Saddlery, just a very satisifed customer.

[dikman]

Beefy, it will be an interesting project for you and while you may be able to design/build something to do what you want it is likely to be specific to your setup. On a personal level my first servo had a needle positioner, I bought it because it sounded like a good idea and I had no idea what I was doing!  I tried it and didn't like it. I find for sewing leather a slow, controllable speed is all I need and an NP is of little value.

[beefy]

3 hours ago, fibersport said:

Get yourself a Kinedyne needle synchronizer for accuracy but I'm pretty sure the servo motor controller is what really controls the functions, the synchronizer is just a switch to indicate where the timing of the machine is.  The Kinedyne is an optical synchronizer and is super accurate.  http://kinedyne-motor.com/products/HM-750SH/234.html You could just get the Kinedyne motor and synchronizer and be done with it.  Just sayin -

Talk to Ryna at http://www.neelsaddlery.com/ 

I have no affiliation with Kinedyne or Neels Saddlery, just a very satisifed customer.

Thanks Fibresport,

the servo IS what normally does the control when it receives the signals from the synchroniser, but my design will command the servo drive based on the needles position.

I've already paid for 2 motors and drives so don't want to buy 2 more LOL. Plus I enjoy this design work and it will be very cheap.

[beefy]

2 hours ago, dikman said:

Beefy, it will be an interesting project for you and while you may be able to design/build something to do what you want it is likely to be specific to your setup. On a personal level my first servo had a needle positioner, I bought it because it sounded like a good idea and I had no idea what I was doing!  I tried it and didn't like it. I find for sewing leather a slow, controllable speed is all I need and an NP is of little value.

Thanks Dikman,

yes this design will be specific to my setup, but my setup is a typical Chinese servo drive, so any time I get a new cheapy servo, if the connections are not identical, I will be able to easily modify them to suit.

You are right, I don't need this so much for very slow sewing but it will be great for other things when I'm going faster. I'm also finding as I'm learning to handle say tarp material or a canvas cover, not having to concentrate on the needle position will make life much easier. I'm also going to make my backstitch foot control so my hands will be completely free nearly all the time.

To be honest this is more a labour of interest rather than a huge necessity. I get very engrossed in the design and programming and the hours tick away quite quickly.
And when the design is completed (and works LOL) I enjoy it every time I use it. 

[nejcek74]

Great project, Beefy! I really like elevated DIY projects, and I hope you succeed. I find the needle positioner extremely useful. What are your plans for the controller — will you use an Arduino or something else that can be programmed? 

In my opinion, you describe the basic functions well. What I would find useful is:

- the ability to check and auto-apply signals from different types of needle positioner, as you already described.

- the ability to easily define the up and down positions by turning the wheel by hand and pressing a button. Currently, on my controller, I can do this either by typing numbers into the controller or by moving the three metal discs inside the positioner mechanically. I always spend too much time fiddling with that.

A more advanced function would be to perform automatic backtacking ((three forwards, three backwards, three forwards, or something programmable) as you are describing, that would be great.!!!!!

[AlZilla]

2 hours ago, nejcek74 said:

more advanced function would be to perform automatic backtacking ((three forwards, three backwards, three forwards, or something programmable) as you are describing, that would be great.!!!!!

If I had this on a leather machine, I'd want it to backtack 3 holes first, then go forward from there. This way I only get the beginning stitches run over 2 times instead of 3.

That's how I do it anyway. This way my first 2 stitches are doubled up as I get when hand stitching.

[beefy]

2 hours ago, nejcek74 said:

Great project, Beefy! I really like elevated DIY projects, and I hope you succeed. I find the needle positioner extremely useful. What are your plans for the controller — will you use an Arduino or something else that can be programmed? 

In my opinion, you describe the basic functions well. What I would find useful is:

- the ability to check and auto-apply signals from different types of needle positioner, as you already described.

- the ability to easily define the up and down positions by turning the wheel by hand and pressing a button. Currently, on my controller, I can do this either by typing numbers into the controller or by moving the three metal discs inside the positioner mechanically. I always spend too much time fiddling with that.

A more advanced function would be to perform automatic backtacking ((three forwards, three backwards, three forwards, or something programmable) as you are describing, that would be great.!!!!!

Thanks for the suggestions Nejcek74,

yes, using an Arduino Uno or Nano for this one. I normally use these boards but program in straight C using Atmel Studio, but for this simpler project will just use the Arduino IDE and "Arduino C". Also adding an external mix of operational amplifier circuits basically because I'm unsure of how the "analogue" output from the microcontroller would affect the servo. Op-amps will give nice smooth variable DC signals. The basic principle is my system will simply "go between" the foot pedal output and the servo speed command input, and "take over". It will monitor the foot pedal output as well as the heel switch, monitor the outputs from the needle positioner, and command the servo to do things accordingly. So basically the servo is nothing but a driver for the motor and it's not even aware a needle positioner is installed. The servo simply does what it's told by my controller, pretty simple really. The most difficult bit is getting the programming correct and foreseeing all the situations that COULD happen. It's so easy to find things afterwards where you say, "Oh yeah, I didn't think of that condition existing at some point" LOL. 

I've pondered the idea of a DIY needle positioner disk, where I can have more than 2 sensors IF there's any benefit to having more than just a needle UP and a needle DOWN position. The rotating disk itself would have just one magnet glued in a hole in the edge. Hall sensors around this disk can be moved to any position to have the needle stop in exactly the desired position. For now though I just want to get the basic design working with an off the shelf positioner. Got one arriving mid January.

Never thought of the idea of automatic back stitch control, good suggestion. I like that one and it could be my next quest. Will have to work out an electrical way to operate the reverse mechanism.

[beefy]

34 minutes ago, AlZilla said:

If I had this on a leather machine, I'd want it to backtack 3 holes first, then go forward from there. This way I only get the beginning stitches run over 2 times instead of 3.

That's how I do it anyway. This way my first 2 stitches are doubled up as I get when hand stitching.

Cheers AIZilla,

interesting suggestion. I'm just a beginner at this sewing gig and all the videos I've watched start of sewing forward then backstitch then forward again and continue.

Would you only start off backstitching with leather but not fabrics, vinyl, etc.

[AlZilla]

3 hours ago, beefy said:

Would you only start off backstitching with leather but not fabrics, vinyl, etc.

Yes. The thicker threads we use for leather create a lot of unsightly bulk when you start forward, back up and come forward again.  And the hole created by the needle isn't really big enough to have 3 stitches run thru. I use V138 and up. 

I start, needle up, where the 3rd hole would be and drop the needle 3 times, backwards. That gives me 2 complete stitches, with my needle all the way down and at the beginning of my intended stitch line. Now I can stitch the "right way"  (forward) and I get 2 locked stitches when I hit the 3rd hole again. 

With domestic sizes of thread and needles on fabric it's not so obvious.

On my machines without reverse, I do the same thing by turning the material around.

Simple to do, but apparently takes a lot of words to explain... 😃