Temporary prototype to permanent prototype!

This is part 3 of 4 in the series Variable Power Supply
  1. Initial design
  2. Shopping!
  3. Temporary prototype to permanent prototype!
  4. Finishing the Power Supply

Now that I had a working system, I needed to make it a little more permanent.  First of all, I wanted dual outputs, so here’s the new schematic I put together.

Simple variable power supply schematic

Simple variable power supply schematic

You’ll notice that the voltmeters are run off a separate battery.  This frustrated me to no end.  Basically, most digital voltmeters *require* an isolated power supply.  You can get high end units that self isolate, but they’re about $100 each.  I wanted digital for accuracy ( this problem only affects digital VM’s – analog would have worked as is ), so I just decided to go with the battery option and see how long it lasts.  I’d be curious what it might have taken to separate off a 9V supply and isolate it from the variable outputs.. I messed with it for a while, but the closest I got was a voltmeter with a pretty heavy bow in it’s accuracy curve. :)


Coming along nicely

Coming along nicely

Anyhow, off to Radio Shack and Fry’s for a few more pieces!  Proto board, plastic enclosure and extra parts to build a dual output power supply.  After I cut the board down and drilled mounting holes, I started moving components from the breadboard to the more permanent proto board.  Here’s a shot shortly after starting to solder.  I mostly used the long leads from the components to bridge everything together.  It’s not the prettiest option, but the cost/speed beats a one-off custom PCB.  Note the beefy heatsinks for the regulators.  An absolute must!  I was reading 145 °F on the heatsink just powering a stamp, LCD and PING))) sensor.


Not easy to use, but it works!

Not easy to use, but it works!

After a couple hours of soldering, fabrication and connecting parts, I had the beginnings of a working lab supply!


Up next, switches, voltmeters and binding posts!

Series Navigation«Shopping!Finishing the Power Supply»

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