388W 5V-30V Lab Power Supply

One of the most useful tools to have in your arsenal besides a multimeter is a good Lab PSU. A commercial hi-current regulated Lab PSU can cost a lot of money (upwards of $400). When I was browsing eBay for stuff, I had come across couple cheap LCD meters from HK. They looked awesome with large digits and cool blue backlit. This gave me an idea. I thought to myself "How cool would it be if I modified an old PSU to become a Lab PSU with most of the bells and whistles!!!" It so happened that I had come to posses couple of 27V/14A telco PSUs some years ago. I had already modified a similar one years ago and it had served me extremely well over the years. It only had a Volt display and was not that attractive. Over the years I was forced to use a multimeter to measure the current which was a bit of a pain in the butt as well as messy with the leads. I had placed a bid on the LCDs and purchased them for around AU$24.00 each. Once I received them it took a weekend to convert the PSU from static to variable voltage.

I had decided to include the following functionality:

1. Has to have 2 LCDs to display the Voltage and actual Current being drawn.
2. Has to have multiple banana outputs.
3. Has to have adjustable voltage output.
4. Has to have pre-set voltage selector for 5V, 9V, 12V, 18V and 24V.
5. Has to have 2 current ranges that will display Amps and Milliamps respectively.

Original Opened New Controller

After stripping the PSU as shown above I cut out holes for the LCDs using a nibbling tool as shown below.

Below is a picture of components needed to construct 2 power supplies for the LCDs (it is not possible to run LCDs of the main PSU as they require 9V) as well as other bits and pieces.

Once I got started it was very quick and easy to wire up.

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