Electronics > Projects, Designs, and Technical Stuff

How I made my SMU

<< < (7/7)

Bees way is a bit low in the melting point. It may be OK for an audio transformer that on average is used only for low power.
I would avoid potting, at least for the first few tries, till you know it is for sure working. Once pottet it would be had to fix.
Oe could try something with a much higher melting point, like rosin, if needed to fix some wires in place.
Idolation on both sides of the shield may be a good idea. It would also reduce the capacitance.

I'm glad you found EI parts supplier. Those are hard to find nowadays.

1, The shielding was quite laborious task. I left small gap in the shielding to prevent short circuit. Overlapping may be easier to do, if the overlapped part is insulated.
I put one layer on insulation tape between shield and windings. Insulation of the magnet wire itself may be probably enough, but better safe than sorry. Enamel should withstand the voltage just fine, if not damaged - I was worried that can happen during hand winding.
2, I used both classic "yellow mylar tape" and kapton tape in my transformers, with good results. Mind that mylar tape was made for this application, has known dielectric strength and somehow lower thickness - so perhaps it's preferred. Be careful with insulation thickness, it adds quite a lot to volume consumed on the bobbin. When buying insulation tape, buy rolls with various width, it makes life easier. Cutting narrow slices of a tape from wider one is PITA job.
3, (you had point 2 twice). I did not pot the transformer, though I bought beeswax just for this purpose - it was fairly cheap, under 10EUR/kg at local beekeeper. My intent with potting was reducing transformer hum (by fixing parts that can move against each other in the magnetic field) and somehow improve cooling of the transformer. At the end I decided not to do this step, because mains hum was nearly inaudible (I had to drop a few drops of thin lacquer on outer EI laminations to "glue" them in place - still easy to disassemble if needed). Leaving it as is also let me back door for transformer modification - if any - as potting it makes repairs/modification difficult. Cooling doesn't seem to be a problem with my transformer.
There are also dedicated synthetic transformer varnish solutions (those are usually even more PITA to disassemble). For ideal impregnation vacuum setup is probably needed, which is something I don't have anyway.

Hi , exciting job, is there any update in your github? I'm expecting repeat your awesome work.

Right now I pushed new release of firmware into the repository - https://github.com/jaromir-sukuba/J-SMU

Major change is rework of USB communication, it works now via SCPI commands, unlike previous communication protocol similar to 'R2D2-talk' of older test gear. Apart from that, I refactored the code and made minor cleanups.
Next update will include user and calibration quick manual.

Thanks Jaromir! I am anxious to see your approach on the calibration issue!


[0] Message Index

[*] Previous page

There was an error while thanking
Go to full version