rewinding 900 ohm solenoid

[coppercone2]

Posted in wrong forum, asked mods to delete original

I have a 900 ohm solenoid from a relay I wanted to rewind.

The dimensions of the electromagnet are 1.2 inch by 0.7 inch and the impedance is 900 ohms, it actuates a HP relay powered by 34V on a RC time delay circuit.

The reason I took it apart is because it was showing low resistance to the chassis (20 meg) while the sister unit shows the usual infinity.

The wire is very thin, measuring 0.109 mm on micrometer, which I believe corresponds to 38AWG
https://www.coonerwire.com/magnet-wire/

Is there a off the shelf cheap tool that can help me do this?

Its about 1500 feet of wire to wind.

I thought this tool might be good.
https://www.amazon.com/PanelTech-Purpose-Electric-Machine-Counter/dp/B07FY9VVQF/ref=asc_df_B07FY9VVQF/?tag=hyprod-20&linkCode=df0&hvadid=242034450866&hvpos=&hvnetw=g&hvrand=4625980874370029592&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003445&hvtargid=pla-597484096296&psc=1

The shaft is 1/4 inch and the original part # is A-121907 (900 Ohms) By C.I. Clare & Co


Like I don't want to buy that coil winder, I feel like I got jumped by this coil anyway. Last thing I was expecting to be bad because it looks great. I thought to just mount it in a drill and try to do it by hand , and hang a small weight on a rubber clasp over the wire so each time I wind a layer I can leave it tensioned. I don't plan on making any more then I have to, 1500 feet seems like alot, but since its just a relay I was going to pack it in to the same dimensions and hope it works.. so I don't need the turn counter.

I also plan on varnishing this, and putting a teflon sleeve over the shaft, I think. The original one was not varnished so when I popped the shaft out to see what was going on, the whole thing failed catastrophically. I was going to use 38AWG remington brand polyamide wire (200C rating) that will be chemically stripped.And I think the wire smelled a little funny.

I can replace it with 2x relays and some kind of time delay circuit, but I thought why not try to keep it original, its nice.. and I get to buy some magnet wire and use the transformer varnish I have...

[Ian.M]

Building an automatic coil winder isn't exactly rocket science.  Nowadays with Arduinos and cheap stepper or servo motors, you don't even need a complex oscillating mechanism to distribute the wire over the length of the bobbin as that can be handled with a motor driven wire guide and a few lines of code.  For the bobbin drive, all you need is a gear motor with a mandrel to fit the bobbin coupled to its output shaft,  and some means of sensing turns to count them so it can move the wire guide motor accordingly.  Since you need the turn sensor anyway, you might as well add a low side N-MOSFET to control the bobbin motor and code a turn counter so it can auto-stop.

Add a couple of felt pads and an adjustable spring pressing them together for wire tension, and a peg to sit the spool on, and that's pretty much that.

[SeanB]

For a relay coil you just need a wooden dowel to fit the former, and an electric drill with speed control. No need to be as exact on the windings, just wind the new coil to the same diameter as the original, trying to keep the turns as even as possible, or a tiny bit larger but still fitting in the winding area, and when finished and tested protect with a coat of PCB lacquer or varnish, and then if wanted a cover of kapton tape, or like a lot of old relays a 2 turn overwind of black cotton thread, that is varnished to make it a solid cover.

[HighVoltage]

A copper wire of 0.109 mm diameter is easily winded up by hand with a hand drill.

Make yourself a little adapter to hold the bobbing firmly and mount the drill, so it will not move around during winding. Then use some leather gloves and guide the wire by hand.

I have wound prototype coils with 0.05 mm diameter wires this way and it comes out better than one would expect.

[jmelson]

Find someone that has a lathe.  Make up some sort of adaptor that will hold the armature aligned to the spindle.  Then, come up with sonething to hold the spool of wire with a springy wire loop to provide a tension relief.  Start the lathe spinning at a modest rate, hold the wire between your fingers and move the wire across the armature to spread out the turns evenly.  If you know how many turns are required, you can rig up a turns counter, otherwise just fill up the coil form.  Make sure you have insulated the armature first, if the coil form doesn't completely cover it.
For a one-off job, simple should be good enough.
Jon

[coppercone2]

The armature has a screw thread on it for attaching to the chassis so I can easily mount it to a long screw with purple threadlocker   Maybe I can have someone hold speed on a power drill (the ones that go slow) while I wind

[Gyro]

Clamp the drill and arrange some form of controlled wire guide. Two people wobbling around will give you zero chance of getting windings anywhere near the end cheeks without going over the edge and ruining the wire.

[coppercone2]

thats a good idea, I will put a chamfuer on the edge of the teflon disks to try to minimize the risk of bumping into it. For the drill I meant to put it in a vise and have someone work as a speed controller maybe.

[Ian.M]

*Most* drills don't have low enough gearing and are too jerky at low speed to be usable for winding fine wire.    If you've got a dead drill with a good planetary gearbox and chuck, maybe see if you can drive its input shaft with another drill to get the additional reduction you need.

[Bud]

20 MOhm leak resistance in 34V environment was a concern ? 

[coppercone2]

IDK it was tripping GFIC maybe it goes down with voltage, I only tested with a DMM. Since I have 3 of the same equipment, I can at least make them measure the same. To me thats a bad sign anyway, they always read open.

The mains switch also had a bad resistance, I replaced it. Perhaps the coil is OK, but I was cross checking the units and I want to make them measure the same at least.

[james_s]

You can get hand cranked coil winders from China for about 40 bucks, they include a mechanical counter to track the turns. I haven't personally used one but I'm told they work reasonably well.

[coppercone2]

I am unsure about the mechanism. I see some that just turn the coil, and some that like slide the coil forward while turning it. Not sure if that would work for such fine wire or how to adjust that mechanism to get the correct traverse speed.

The one that moves the bobbin on its axis would allow for like auto winding but I was not sure if it was good enough for such delicate wire and how adjustable it is. I have not found any video that explain it well. I would imagine you need to adjust it for wire and coil dimensions some how. Does that have V belts in it or something?

[ingalopez]

Check for Youtuber Restore Old Radios. He is rewinding a field coil of an antique speaker, right now. He uses not much than a hand driven  wire.

[Hamelec]

something like that:
https://www.amazon.de/Connex-COX801006-Handbohrmaschine-6-mm/dp/B001BAYFUY/ref=sr_1_4?keywords=handbohrmaschine&qid=1673370598&sr=8-4
clamp it in a vice.
You can easily count the windings.
And take a piece of threaded rod, a few nuts and washers.
Guide the wire by hand.
done.

[coppercone2]

Excellent idea forgot I had one of those.

[james_s]

something like that:
https://www.amazon.de/Connex-COX801006-Handbohrmaschine-6-mm/dp/B001BAYFUY/ref=sr_1_4?keywords=handbohrmaschine&qid=1673370598&sr=8-4
clamp it in a vice.
You can easily count the windings.
And take a piece of threaded rod, a few nuts and washers.
Guide the wire by hand.
done.

Why do that when you can buy a purpose built winding machine for not much more? https://www.ebay.com/itm/374435770081

[Hamelec]

something like that:
https://www.amazon.de/Connex-COX801006-Handbohrmaschine-6-mm/dp/B001BAYFUY/ref=sr_1_4?keywords=handbohrmaschine&qid=1673370598&sr=8-4
clamp it in a vice.
You can easily count the windings.
And take a piece of threaded rod, a few nuts and washers.
Guide the wire by hand.
done.

Why do that when you can buy a purpose built winding machine for not much more? https://www.ebay.com/itm/374435770081

        ..because he and i had one of those. 

[coppercone2]

the main reason is that thing is huge and its built bad like exposed gears. I don't think a hand powered one is a safety issue but I would need to make a box to store it in, and its big. Like dust oily gears, I know its going to look like hostile biology in a few years. Really dodgy though if you connect that to a drill and you have exposed gears though. I really hate exposed gears & belts (I mean like a belt belt, not a o-ring micro lathe). Smelly exposed gear oil, no thanks.

I will try with the hand operated drill first because I can risk wasting a bit of magnet wire (I got enough for a few coils on a spool).

[coppercone2]

well I got problems because the teflon heat shrink looks like its made out of like.. strips that are kind of like corrugated pipe after you heat it, so the coil shape is of a spiral noodle piece (out of round with a helix slightly), so the windings are not going on nicely after the first layer. I will try to finish it though and see what happens, if not, I replace it with a custom relay PCB

I am using a right angle battery drill with speed adjust, a soldering reel holder and my hand to wind it. Considering the time, technique and machinery setup/materials needed to do this right, engineering a PCB that does what this relay does is easier for me then the mechanical version. But it might work, who knows. If you need a break you can jam a clean paint brush over the wire so it rests with a little bit of tension on it. It would also be much easier if they made magnet wire that is striped like a snake, so you can see optically whats going on, instead of copper on copper, like imagine every 2 inches were changing colors from black to c opper.


edit: wire ripped for no reason after I finished 30% of it. Going to see if I can redesign this with some regular relays. I think its because I lost concentration since its phenomenally boring to watch the coil grow

[coppercone2]

I realized that the smaller capacitors I put in this open up alot of room where I might be able to fit a 36V relay that I thought was a bit too big off ebay.

[coppercone2]

trying again, but it will be a https://en.wikipedia.org/wiki/Coil_winding_technology#Wild_winding

but since i laminate it, maybe the varnish will account for the slightly different current consumption of the wild wound coil, and the thermals will work out, and it might work. 

well I wound something, I will test it tommorow after I rest, I need to deal with terminating the magnet wire, I called it a day because i will rip something if I work more today... gotta be careful with the magnet wire

I hope they put a wide margin of tolerance on that 900 ohms. I can still splice it and put more windings on it too I guess, but the bobbin is pretty full, I wonder if I need to give it a bit of a belly , fatten it up a little.

[coppercone2]

I got it to 900 ohms. bit un even though, if you were to flatten it out, it would be very similar to the old coil in terms of size, I don't think it was wound super accurate to begin with. Winding the full bobbin I had 1100 ohms or so, so I had to unwind.

[coppercone2]

I am putting a piece of heat shrink over it with two triangles cut out that will hold the soldered wires to the magnet wires but also allow varnish to infiltrate the coil. Then I will put another heat shrink on it when its cured to give it a total cover.

[coppercone2]

Ok, The inductor is just a hair too small, when I varnish it I will take off the top plate (teflon) of the bobbin and make it thinner, or file around it, but it looks like it has enough strengh to activate the relay. I did not realize the top disk was 0.5mm higher then the core.

I would say you can do this with a slow speed right angle drill (with the thumbwheel adjust) and a soldering iron holder. Just buy enough wire for like 3 attempts, because it took a while. But what I am saying is that I think you can get the correct field strength without worrying too much about the windings being perfect.