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Archive for November, 2010

DIY Bench Supply Summary

November 30, 2010 1 comment


I’ve updated my bench power supply project description with a summary of the project (as follows):

Project Summary

This project started as me trying to fulfil a need for a reliable and convenient power supply and wanting to learn some lessons along the way. I designed the project in sketchup and then proceeded to go through various stages of construction. There were a few design changes along the way but nothing major. I decided to add an external voltage probe and a switch to allow voltage measurements either from the ammeter or ground.

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Power Supply – Case Completion

November 26, 2010 13 comments


I’ve finished most of the construction and i decided that this project has taken longer than i’d hoped. I wanted to finish it so here is the final build and assembly in one huge post.

Parts Used:

  • My Adjustable Voltage Circuit
  • My Panel Meter Circuit
  • My Aluminium Supply Case (Labelled)
  • 2x DPDT switch
  • Green Binding Post
  • 4x Red Binding Post
  • 4x Black Binding Post
  • 3mm Red LED
  • 6x 3mm Green LED
  • 7x 3mm LED panel clips
  • 4P2T rotary switch
  • Amp Panel Meter
  • Voltage Panel Meter
  • Red Multimeter Lead
  • 2x 6mm knobs
  • ~20cm of 3mm 3:1 Heatshrink
  • 2x TO-220 heasinks
  • ~50 Crimp terminals
  • Lead Free Solder
  • 3x 47 KΩ resistors
  • 3x 5.6 KΩ resistors
  • 3.9 KΩ resistor
  • 820 Ω resistor
  • 12 KΩ resistor
  • 1.8 KΩ resistor

Tools Used:

  • Soldering Iron
  • Crimping tool
  • Snipe nosed pliers
  • Wire cutters
  • Glue Gun
  • Phillips screwdriver
  • 2mm Allen key

For most of this it should be clear how it goes together. The circuit construction just followed my power supply schematic. If there is anything that needs explaining further then feel free to ask. Unfortunately i got a bit carried away at some parts and forgot to take photos, I’m still learning to take my time.

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Updated Bench Power Supply Schematic

November 10, 2010 14 comments

You may have noticed that my previous post shows strange labels for the rotary switch. This is because i’ve changed the function of the rotary switch.

The ammeter causes a small voltage drop and so when the ammeter is being used as ground, the effective supply voltage is different to when the actual ground is being used. As such i’ve made the switch have the following options for the voltage measurement:

  1. Variable voltage to Ground (VG)
  2. Variable voltage to Ammeter (VA)
  3. External probe to Ground (EG)
  4. External probe to Ammeter (EA)

As such the previous schematic for the power supply needs updating. Below is the updated schematic:

I think this is a slightly more useful design as it allows me to compensate for the voltage drop across the ammeter. The only function i lose is the ability to measure the fixed outputs. But considering the external probe should be able to do this, i don’t really mind.

Aluminium case finishing

November 10, 2010 4 comments

The power supply is coming along nicely. The case is built but needs some improvements and finishing touches. I plan on using this supply for some time and so want it to look as tidy as possible. I finished the case by routing the cables and putting labels in appropriate places.

Parts Used:

  • Dry transfer lettering (Letraset)
  • Permanent marker (Sharpie)
  • Clear Coat spray

Tools Used:

  • Pillar drill
  • 4mm drill bit
  • 8mm drill bit
  • 12mm drill bit
  • G-clamp
  • Ruler
  • Disposable gloves
  • PCB cleaner (citrus degreaser)
  • Craft knife

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