FATAL ERROR WHILE COIL WINDING READ

[bernte_one]

Sorry for this posting but i think there are many people out there which will be the victim of murphys law.

The last times i made coils on my easy coil winder like many other here in froum with wood plate and these good wooden sticks. Winded by my own hands turn by turn.

Now i had the idea to make a simplier coil winder, it contains ball bearings, metal screws instead of the good wood sticks and a calculator which is modified to a counter with reed switch- nice thing i thought i was so proud of it.

But when i did my tesoro coils last weekend i had a bad awakening- i measured the coil inductance so that i had exactly the coil specs that were right. But i measure when coil were placed in my nice machine- with all these metal components - i couldnt imagine that these parts will influence my testing result.

I take the coil off glued it and taped it and test it again the inductance driftet to a lower result - this cant be i thought. After tighten the coil on my machine the windings had the exact specs and the only thing what can happen when i taped it that it rises a little little bit.

But now after drinking my friday evening beer after a hard working week it came to my mind - sh*t metal trash- i run into my lab and tested my coil on the winder and off coil winder- that is it.

So keep in mind - DONT measure your coil inductance with any metal parts nearby. You CANT get the right result.

Tomorrow i will change all metall screws with nylon bolts for first.

So good night.

[satdaveuk]

Did that mistake in the early days bernettie,( check out my very early postings and pics,) my coil milling machine is spot on everytime far as windings very accurate but I learn to subtract the difference the machine effects the coil inductance which has large DC motor drawing 1.5a 12v underneath and a old push bike back wheel bearing assembly which is used for the drum drive plus large steel plate which suports the upper and lower drum assembly, but may I add easy to forget like checking components before placment, I say to my appentice along time ago how important component values are in some/all circuits and always check them out before soldering them in PCB , and now he is so careful , good engineer l trained by me, like my dad trained me and so fourth .

regards

[John in NC]

I made that mistake on my bench test. My bench had big long screws in it. I now have a plastic test bench that puts my coil out of reach of any metal.