Simple power supply

Andrew Leech AndrewLeech at
Fri Sep 19 12:01:01 EST 1997

In article <5v74tp$qdi at>, kang at says...
>Dear colleagues;
>I recently developed new power supply which is totaly different from the convent
>ional one in that it does not use the core and coil and condenser for transformi
>ng AC to DC. Instead I used bridge diode just to change the AC to directional pu
>lse current. 

It's been done. We have a gel electrophoresis system called "Mupid-2", made
by Cosmo Bio Co Ltd of Tokyo, Japan.
Although the circuit diagram is not given in the manual, its characteristics
are almost exactly the same as yours, and it does say "no transformer is

>I made the beta version of this apparatus and wanat to sell with 40 dollars.

You might want to check it hasn't been patented first.

In article <wqIErKAYO6F0Ewki at>, duncan at 
>This would be 'illegal' in the UK/EEC due to lack of safety and would
>not be allowed to be sold. If one of the rectifiers fails short circuit
>you can get full mains AC on the output with lethal consequences.  With
>no current limiting this would kill. Given that a transformer and
>condenser are literally only a few dollars surely it makes sense to use
>that route?

I wasn't in the lab when it arrived, so where it came from...? Anyway it
is well fused and has a cutout switch in the gel tank to stop you frying

Ironically though, because the mains supply in the UK is 230V, it has to
be supplied from a small step-down transformer, so it is isolated.

Personally I don't like it - but that may be because the gel trays are
rather small and fiddly for cutting out bands, and of course you only have
"slow" and "fast".


Email: a dotte leech atte uea dotte ac dotte uk - U-no-Y!
Andrew Leech                 *All opinions personal
Biological Sciences          *
University of East Anglia    *If you don't like it,
Norwich, UK                  *    don't eat it.

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