New version of K2636 gives strange unlinear control of motor

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1

In a project I’m using a k2636 kit to control the revs of a sewing machine motor. I had a kit which worked fine - untill it went dead. I think I broke it stuffing it into a mounting box that wasn’t quite big enough (so I’m not complaining about that). I wasn’t able to fix it, so I bought a new kit to replace it. This kit was a newer version (the one with the power LED). And once asembled it worked fine … except; the control of the motor revs is suddenly far from linear.

I’m far from electronics savy, so forgive me I get some terms wrong. Turning the trim potentiometer from 0% to about 5-10% controls the motor in that range, but then it hits a point where the motor, over 2-4 seconds, revs up to around 50% speed - and the rest of the potentiometer range (from 5-10% to 100%) will control the motor revs from about 50% to 100%. For this particular project I’m mainly interessted in using and controlling the lower range of revs, so this is quite a problem. The old version of the kit gave me a perfectly linear control of the motor from 0 to 100% - and once set on a speed, it would keep that speed steady.

I have tried swapping both the potentiometers with the ones from the older version of the kit, but that gives the ecxact same result.

So what is wrong with this new kit (or the new version of the kit)??

Is this just how it works/is it designed differntly to prioritize the higher rev range?

And is so; is there a particular component I can change to make it work like the old version?

Or, is the kit I bought faulty?

And is so; is there a particular component you would suggest changing (I still have the older version, so I can harvest components from that) or should I return the whole kit and start from scratch??

Or, is it something else wrong?

And is so; what do I do about that??

Thanks in advance!

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There is no hardware difference between the old version of the K2636 and the new K2636.
We just re-design the PCB and we using another transformer.
The production is already 1 year changed w/o problems, so there must be something wrong with your kit or the load (motor) is no a compatible (serie motor).

You can change the triac and see the result, test it first with a standard 220V lamp.
Check that the transformer voltage and the load input voltage in ‘in phase’.

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Thanks for your feedback!

I have tried changing the triac (to the one from the older kit) - but it works just the same. Testing with the 220V lamp produces slightly different potentiometer/load range - here the first 0% to 20% turns the light step-less up a curtain point where it stays steady until the last 90-100% where it jumps to full power in a few steps.

I have checked that the transformer/load input voltage is in in phase. And the motor I’m using is the same as I used with the old kit - and that worked fine - so I don’t think the motor is the problem.

Is there something else I can try changing or should I return the kit??

4

It could be a lot of things, difficult to say by mail, maybe you can send the unit via your dealer ?