EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: david77 on April 15, 2012, 12:25:27 am
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Have you ever felt the need for a 0-350V lab power supply? If so then this might be the right thing for you:
http://hpm-elektronik.de/ng350-0400-netzteil.htm (http://hpm-elektronik.de/ng350-0400-netzteil.htm)
The description is in German but the circuit is self explanatory.
As I play around with tubes sometimes I have felt that need several times, but never had the time or the parts to build one. Now over the easter weekend I found a box of nixie tubes while clearing out some old crap. I wanted to test them if they still worked but there was that old problem again: Where to get 150V DC at short notice?
So back in the box the nixies went again.
On easter sunday morning I visited a local fleamarket and picked up an old isolation transformer in a nice case for a couple of Euros. I didn't need it as such as I allready have one but I figured the transformer and the case might be the ideal base for a HV lab power supply.
I also found the link above and decided to use that circuit instead of making up my own. I had to change it a little to suit my needs and the parts I had better but it is mostly unchanged.
The old isolation transformer turned out to be quite ideal for a PSU of 350V at 250mA. The case is a bit small but I managed to shoehorn everything into it.
It's adjustable from 0-350V, short circuit proof and provides CV and CC mode.
The chassis is made of FR4 PCB pieces soldered together. I like using PCB material for cases, it's cheap and very easy to work with but still very strong. The chassis holds the electronic and slides into the case that I've got from the isolation transformer.
I've tried something else for the frontpanel this time. It's simple A4 printer paper stuck to the frontpanel and then covered with a sheet of laminating foil. The laminating foil can simply be ironed onto the paper. It protects the paper and gives it quite a nice finish. This works rather well.
I decided to use analog meters for this PSU, it would have been hard to fit digital panelmeters into this case and I had two identical 100µA meters to hand anyway. The scales are custom made to my needs, just a bit of Photoshop magic.
Now, where did I put those nixie tubes?
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I prefer equipment that makes it less easy to hurt/kill myself ;). Especially with the large 100 uF cap on the output, is this really necessary for stability?
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In the old days of tubes, 100-300V could have been used, but much less applicable today. However, high voltages remains common for high energy physics work, including lab exercises.
If you are so inclined, the defunct Power Designs company made them by the bushels, and they are now cheap, if you need them. As high voltages are dangerous, the quality of the construction, safety electronics, and connectors are very vital. You can find PD surplus supplies up to 15kV.
Here's one example, $170, 2kV, 10mA, $24 S&H in the USA.
(http://imagehost.vendio.com/a/35105687/aview/PowerDesigns_2K-10.JPG)
Another option are gel electrophoresis PSU can be found easily to 3kV and more power output, compared to PD lab grade supplies. I got one for $25. Here's a transformer based one for $40 to 1kV.
(http://dl.dropbox.com/u/22198698/Images/Auction/2012/04-12/Buchler-040312.jpg)
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DIY is good . Nice looking front panel there, many years ago I did some panels in 3 colours, using a copier that we had, that had 3 different toner colours in cartridges, where the print would be in the colour that you placed into the machine. Took a few dozen passes to get the usable ones, as I went through a print, adjust, print, change cartridge cycle. Did around 40 pages initially, with the artwork being 3 sheets of laser printed black. Laminated afterwards and stuck to the front panel after cutting to size, with spray glue ( i only was able to use that can of glue once, the next time it was gummed up, even though the nozzle had been cleaned according to instructions) and careful alignment. Holes were drilled for all the LED's and switches after the glue was dry.
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I prefer equipment that makes it less easy to hurt/kill myself ;). Especially with the large 100 uF cap on the output, is this really necessary for stability?
No, it's probably not, I put a 15uf into mine. Also I only used one 220uf cap instead of 4x 470uf, I think thats a bit overkill and scary.
I haven't had time to conduct stability test under different loads yet, just some test with resistive loads and so far all looks good.
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Here's one of my more 'fun' PSUs.....
Not surprisingly it didn't come with the front-panel screw terminals - I had to add those to holes already in the chassis hidden by the label.