[time-nuts] FW: Favorite DC power Supply?

Didier Juges didier at cox.net
Fri May 2 19:39:26 EDT 2008

 Here are my 2 favorite power supplies.


The one on the left is a 30V/3A supply. The current limit is adjustable with
a 10 turns pot, so it can be precisely set. I only use 3 turns of the 10
turns pot, so that one turn is one A, resolution is 20mA. I find it
extremely convenient to be able to precisely set the current limit without
having to use another instrument. When in current limit, the lower LED turns

It has a variable speed fan, so that while small, I can use it at any
voltage/current setup, but it is only noisy when it's working hard. The
transformer uses a dual C tape wound core, and while small, it occupies the
vast majority of the space in the box, the rest being the filter cap. Ther
electronics uses whatever space was left around those parts. The heat sink
in on the back side, in the open, with the fan blowing across it.

The meter can display V or I, and when you press the small push-button, the
scale is 1/10th (0.3A FS).

It is very low noise and stable, with a good voltage reference. It will also
sink current at the programmed value, convenient to check batteries.

It was completed about 10 years ago, but I have improved it since with a
better reference, better op-amps and better compensation for better
ripple/noise/transient response.

The one on the right is an oldie, I started it while in college. People who
were not yet born now have their own children going to school...

It is a tracking, dual adjustable output supply, with a 10 turns pot to
adjust the voltage in 2 ranges, 0-10 or 10-20V with about 0.5A max current.
This one is not current limited, but it trips very fast and shuts down if
the current is exceeded (it has very small output capacitance). I found that
preferable when working on sensitive analog circuits. You can set it to 10V
and connect it to the B-E junction of a small bipolar transistor without
blowing it. It also has a third output, nominal 5V/0.5A that is adjustable
in voltage or can be switched as a constant current output 0.05 to 0.5A)
with the screwdriver type front panel potentiometer. It is also convenient
to charge batteries.

I also have a number of commercial supplies, by HP, Topward and Powermate,
with higher voltage and/or current capability when needed, but these are the
ones I use all the time.

Both are pretty small, the big one is 16 x 7 cm (6.3"W x 2.75"H) across the
front (the current fan is a little taller...) That's another reason I use
them all the time.

Didier KO4BB

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