# Adding variable speed to a SS that doesn't have it.



## Skeety (19 Sep 2015)

*UPDATE:

Thanks to Scrimper for the heads up, I had completely overlooked that the Hegners have induction motors. This speed control should NOT be used on anything that has an induction motor. Fine for things with normal brushed motors.*

Hi All,

When I bought my Hegner earlier in the week it turned out that the "Variable Speed" was down to shocking wiring in the foot pedal.

Wasn't too bothered as I got the Hegner at a decent price but figured that as the Record had it maybe I would like it for cutting thinner material and also teaching my other half to use it.

Some of the offerings on the market are bloody expensive for what they are. Initially I started looking for circuit diagrams as I used to make these things over 20 years ago when I worked for a tool hire company, made the PCB's etc. Research led me to eBay where i found and SCR controlled voltage reg and duly ordered one.

It arrived this morning and after finishing the dust extraction project started on the speed control project, pulled out some bits from previous projects and began assembly.

The pictures below show the process, basically position speed controller hole for the potentiometer in the box with enough room to wire it. Mark the cable for feed and load, figure out the wiring (no diagram supplied) the Neutrals are commoned on the back of the board as it's always controlled on the live side. Normally the supply and load side would be obvious if you bought a speed controller with a plug and trailing socket. Out was marked on the board. Next step was crimping up the fly leads (i'll be hard wiring in series and getting rid of a load of excess cable and connections) Then connecting the cables to the controller. The Earths are just connected together.

Any questions let me know. Mods, please feel free to move, posted it in here first as it's probably most useful here and I have had a lot of help about the purchase of a Hegner SS.

This controller is rated at 2000W (2KW) I would not run it at that constantly, the Hegner is only 100W as are most scroll saws so well within it's capability 

Pictures are here:

https://www.dropbox.com/sh/12lh0mzsi3ml ... Zzpca?dl=0

Cheers,

Jon.


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## martinka (20 Sep 2015)

Interesting. I wouldn't mind variable speed on my Multicut S2 so that I can slow it down to cut thin brass.


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## Skeety (20 Sep 2015)

If anyone is interested i'll post a parts list and instructions 

The IP65 box, glands and cable I already had but even if you had to buy everything you would get change out of £15. With a trailing socket and plug it could be used to control anything 

Jon.


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## martinka (20 Sep 2015)

Skeety":12hifl2d said:


> If anyone is interested i'll post a parts list and instructions



That'd be me then.


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## Skeety (20 Sep 2015)

Here is the parts list:

Toolstation:

1 x 37079 - 2M Single Extension Lead (cheaper than buying the plug, socket and cable)
1 x 48151 - 93mm x 93mm x 55mm IP 65 box (keeps the dust out and strong)
1 x 80473 - 10x White Cable Glands (Nearly the same price as buying 2 from somewhere similar)

If you don't have crimps or bits of terminal block you will need to sort them too. I used crimps in mine as I had them.

The Speed controller is from eBay here:

http://www.ebay.co.uk/itm/Adjustable-Vo ... 51c01a6245

I'm not the seller and don't have any connection to them.

Will follow with the wiring diagram tomorrow.

Cheers,

Jon.


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## scrimper (21 Sep 2015)

I don't want to be a killjoy but have you actually tried this with your Hegner? All the Hegners I have seen are fitted with induction motors and in general the type of speed control shown here normally only work with series wound brush type motors. 
The speed of most normal induction motors is controlled by the type of winding and the frequency of the supply and generally cannot be controlled using these electronic speed units.
If it does work I would be careful that using one for more than a short time may damage the induction motor.
With most induction motors the speed variation control is only available factory fitted.

I would be most interested how this control would work with a Hegner fitted with an induction motor?


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## Skeety (21 Sep 2015)

Thanks,

Will double check, the supplier listed the controller as compatible. I have tried it, all be it briefly.

Jon.


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## scrimper (21 Sep 2015)

The control you list above uses a SCR (Sometimes they use a Triac) which removes part of the waveform to reduce the power to the device, they do work with many things such as lights and indeed any series wound motors such as those used in vacs and also in auto washers but are not really suitable to control induction type motors, you can get devices that will vary the speed of induction motors called *variable frequency drives* but they are very specialist and expensive and probably only work with motors designed to use them.

Up until the 1970's all washing machines were fitted with induction motors and they used gear boxes and variable clutches to control drum speed, when electronic speed controls became available most makers switched to series wound motors (carbon brush motors) so that they could control motor speeds electronically and do away with the gearboxes etc.

Induction motors are very much more reliable than the series wound type and often outlast the device they are fitted to, when buying fixed woodworking machinery I always choose a machine that uses induction rather than series wound, apart from the reliability induction motors are smoother with much quieter running!

(FWIW I spent most of my working life in the maintenance and servicing of all types of electrical apparatus electrical and electronic)


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## Skeety (21 Sep 2015)

Scrimper,

You are absolutely 100% correct. Apologies for saying this could be used with the Hegner, I completely overlooked the fact it had a induction motor.

It will be fine for anything with brushes.

Cheers,

Jon.


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## scrimper (22 Sep 2015)

Skeety, thanks for your understanding, I hope you didn't mind me pointing the problem out.  

John


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## martinka (22 Sep 2015)

Damn! I was hoping Skeety had come up with something that worked with induction motors. I knew there were problems with adding variable drive, from previous threads in here, but I was hoping some clever Chinese person had come up with a miniature electronic solution.


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## Skeety (22 Sep 2015)

scrimper":3plj75qh said:


> Skeety, thanks for your understanding, I hope you didn't mind me pointing the problem out.
> 
> John



Absolutely no problem at all! Many thanks for posting something I had completely overlooked 

Cheers,

Jon.


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