Hi folks, my first post here (waves!).
I'm knocking together a little power unit (~8 to 25 volts, 3-5 amps) for electro-etching, where the output needs to be switched from DC to AC during the process, and this bit of course is easy.
My problems start when I want to be able to control/adjust the unit output voltage for both AC and DC. With some trepidation I tried one of those low cost 240v/2kW 'motor controller' dimmers from ebay on the transformer input since I had a couple to hand, and it all seemed to be working OK, panel meter reading the voltage correctly etc. and I thought I'd gotten away with it.
In fact I was just about to hot air gun all my heat shrink and fasten up the enclosure before I realised I hadn't done a load test - made some saline soaked tissue as the etch simulation and pushed the etch wand down, and the panel meter light went out before any current draw was even displayed. Checking the transformer AC out showed me the transformer was not supporting the load with the voltage dropping from ~24 to about 1.3, and my fears about the dimmer output waveform being no good for driving the transformer were realised.
There's no way I can afford to buy a sine-to-sine wave dimmer, and who would for such a little project, and no way I'm going to start trying to build a dual IGBT unit myself or anything (I used to be a little better at this sort of thing, but my brain is going to mush these days), so I'm wondering if a simple solution like a capacitor alone across the output of the dimmer/input of the transformer might not do enough for the waveform to render it more palatable to the transformer? If so what type and value should I be in the ballpark with?
Help!
Thanks in advance, and Kind Regards,
Shaun/FloWolF
I'm knocking together a little power unit (~8 to 25 volts, 3-5 amps) for electro-etching, where the output needs to be switched from DC to AC during the process, and this bit of course is easy.
My problems start when I want to be able to control/adjust the unit output voltage for both AC and DC. With some trepidation I tried one of those low cost 240v/2kW 'motor controller' dimmers from ebay on the transformer input since I had a couple to hand, and it all seemed to be working OK, panel meter reading the voltage correctly etc. and I thought I'd gotten away with it.
In fact I was just about to hot air gun all my heat shrink and fasten up the enclosure before I realised I hadn't done a load test - made some saline soaked tissue as the etch simulation and pushed the etch wand down, and the panel meter light went out before any current draw was even displayed. Checking the transformer AC out showed me the transformer was not supporting the load with the voltage dropping from ~24 to about 1.3, and my fears about the dimmer output waveform being no good for driving the transformer were realised.
There's no way I can afford to buy a sine-to-sine wave dimmer, and who would for such a little project, and no way I'm going to start trying to build a dual IGBT unit myself or anything (I used to be a little better at this sort of thing, but my brain is going to mush these days), so I'm wondering if a simple solution like a capacitor alone across the output of the dimmer/input of the transformer might not do enough for the waveform to render it more palatable to the transformer? If so what type and value should I be in the ballpark with?
Help!
Thanks in advance, and Kind Regards,
Shaun/FloWolF