Posted by aonomus on September 1, 2008
Ok so a few people have been wondering just what I’ve been up to recently so here’s the list!
First I worked on the secondary coil of my mini SSTC, then I decided to make a 450V boost converter based off of Uzzor’s 450V boost converter with a few improvements.
The 450V boost converter is a 555 based boost converter and when powered with 12V at 3A can charge ~5000uF in 1-2 minutes and seems fairly efficient. I decided to give both the IRFP450 and the diode heatsinking, so I isolated the diode (tab is equivalent to HV +) allowing the heatsink itself to stay at 12V when the charger is running. When I’ve finished tweaking it, I will publish the information, schematics and PCB images, but I may have to redesign the PCB so beware when trying to duplicate the design (there are 2 errors greenwired underneeth the PCB).
After I built the charger I assembled my mini cap bank from the only 450V capacitors I could obtain at the time; 200V capacitors appear to be much more available at a industrial surplus store so I may eventually try building a charger for lower voltages. The copper buss bars are made using 1/2″ copper water pipe flattened in a vise, giving a fairly satisfactory result (others have sworn by using a hammer + wood block, however some have said that the hammer method gives them curved buss bars). The SCRs are stud mounted ‘mystery’ SCRs I picked up for $5 and the SCR will allow lossless switching (compared to other amateur coilguns).
I’ve also been busy expanding the storage on my workbench and squirreling away parts before the school year begins and I’m inundated with too many other things to clean the bench up (Before and After photos follow).
In my frenzy of obtaining parts for projects, I have ordered from Electronics Goldmine and a company called ‘Futurlec’. I recommend Electronics Goldmine however I seem to be getting a bad customer experience from these guys so if/when I receive my goods I’ll do a writeup reviewing their quality/performance. All that is left is a Digikey order for those ‘hard to get’ things like specific resistors, inductors, sil-pads and nylon washers.
From Electronics Goldmine, I ordered some torroids for gate drive transformers, a bunch of 0.1uF ceramic mono-caps, 4 big 1000V 1uF polypropylene capacitors (for tank caps), and an assortment of capacitors, inductors, diodes and other bits.
From Electronics Goldmine, the ‘Gold Pack’ category is all just parts assortments with even $3 boxes of ‘everything’ which are really tempting for my next order from them in the future. Below is the ‘Gold Pack 7‘, and I was lucky enough to get 4 matching inductors, a boatload of 1uF tantalum caps, some poly caps, trim pots, diodes, electrolytic caps, and some possible ‘precision’ resistors. A little dissapointing was the ‘watering down’ of the pack with extra screws and nuts. For international shipping, the size/weight of the screws may affect shipping to some countries.
Among the other cool shots, the 1uF 1000V polypropylene caps that I’m testing for tank caps. While they won’t be any CDE 942c’s, they have no datasheet and on my mini SSTC could even have breakthrough and fail [catastrophically]. It could be entertaining, or expensive, but at $2 a piece I couldn’t resist.
Last but not least with all the squirreling away of parts I would like to thank ST Micro for sampling some power semiconductors. I would take photos of my power semiconductor collection for giggles but my workbench is full of parts to be sorted to bins.