bench power supply

mik000000

Member
2006-10-16 5:30 pm
while working on another i had a need for a dual bench power supply and came across this.

Dual Adjustable/Variable Power Supply Circuit Using LM 317 & LM337

it is nice and simple and i have most of the parts already. any tweaks to improve it?

dual-supply.jpg
 
I have several low voltage bench supplies. Several are Heath, I sold a B&K, and there are others. The nice feature of many of these sorts of supplies is that they can be configured as tracking - meaning one adjustment controls both. The outputs float, so you can connect them as V+ and V- supplies, or both one polarity. They can also operate independently, so you can have say 12v and 18v supplies for whatever. And also they offer current limiting. You can short the output and dial in the amount of current it will provide. So I can limit current draw by a circuit by setting it before hand.

And of course voltage AND current meters.

Here is the manual for the B&K 1601 as typical. It includes the schematic at the end.
ftp://ftp.flippers.com/TTL/TestEquipment/B&K/B&K_1601_Power_Supply.pdf
 

tomchr

Member
Paid Member
2009-02-11 12:58 am
Calgary
www.neurochrome.com
Beware that in both schematics posted so far, the output voltage of the regulator will shoot up if the pot wiper fails or bounces on the resistive track (common failure mode for pots). That could kill the attached circuit. Been there. Done that. With a commercial supply no less.

Before you get too far in the build process, I also suggest taking a look at used power supplies. The HP 6237B is a workhorse supply. 0-18 V @ 1 A; 2 x 0-20 V @ 500 mA, tracking or independent. They're typically available for less than you end up spending just on the heat sink, chassis, and transformer if you build your own.
Just a suggestion. It all depends on whether you need a power supply now or if you're in it for the build and learning experience.

Tom
 
You can precede the regulator with another LM317 set as a Constant Current Source (CCS),
This can be fixed at 1A, or more, or can be switched to a variety of lower CCS values.
Protects both the regulator and the DUT.

The CCS circuit is in the 317 datasheet.

A 2x6W rotary switch is available very cheaply to give you 5 different CCS settings for the two regulated outputs.
 
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