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Archive for the ‘DIY Bench Supply’ Category

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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Aluminium case construction

September 24, 2010 3 comments

or aluminum if you prefer.

This has taken a while to put together as I don’t have any power tools of my own, so I’ve been borrowing others.

Parts Used:

  • Aluminium Sheet – 0.5mm x 500mm x 500mm
  • Two part epoxy glue (Amazon, uk)

Tools Used:

  • Ruler
  • Permanent marker
  • Aviation snips (Amazon, uk)
  • Dremel 300 (Amazon, uk)
  • Dremel SpeedClic cutting disk (Amazon, uk)
  • 2x square edged wood planks
  • square edged desk
  • G-clamp
  • Pillar Drill
  • 4mm drill bit
  • 5mm drill bit
  • 8mm drill bit
  • 10mm drill bit
  • rat tail file (round file)
  • de-burring tool (Amazon, uk)

I started with a big sheet of 0.5mm thick aluminium. I had already decided on the layout of the components on the front so it was just a case of drawing it on the aluminium and cutting it out.

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Bench Power Supply Schematic

September 14, 2010 1 comment

Note: There is an updated version of this schematic here

I’ve been unable to get to the tools lately to finish off the bench power supply case, so thought i would do an update for people looking to do a similar project.

I’ve drawn up the circuit schematic for the bench power supply. I’ve given colour coded labels for the cables coming from the ATX power supply (correct according to wikipedia at time of publication) and shown all the circuits that are needed, including all component values that I’ve so far decided on. The resistors attached to the LEDs will be chosen at  later date, hence those have no values in this schematic.

I hope you find it useful

edit: I should add that i have some planned upgrades to this, such as relays to switch the binding post outputs based on the state of the power good line. This should protect any equipment from unstable voltages when the supply is first turned on. Also I would like to put resettable fuses in line with the outputs to prevent over loading any of the components. These are complications that can wait though. For now i just want to get the basics working.

Panel meters arrive!

July 29, 2010 14 comments

The panel meters for my DIY bench top power supply have arrived from china. One is a 20v voltmeter and the other is a 5A ammeter. I ordered them from ebay and at a cost of around £6 each, they are far cheaper than anything available locally.

On unpacking the meters i found this rather interesting note:

(excuse the crappy photo)

It seems that the meters require fully isolated power supplies. It may be possible to power them from battery but then i have to mess about with relays switching them on and off and changing the batteries. Instead i hunted around and ordered some of these DC-DC modules. They are XP-Power IA1209S modules but any dc-dc module with between 9v and 12v isolated output will do. I chose these because they have a 12v input, 9v output and are cheap. They have dual outputs but this just means that they provide a -9v output as well as the 9v output. Obviously the -9v output isn’t needed.

Panel Meter Power Circuit

Parts List:

  • 2 XP-Power IA1209S dc-dc modules
  • Small piece of strip board (also called vero board)
  • Solder
  • 6 lengths of multi-core wire (7/0.2mm core)

Tools Required:

Only basic tools are required for this circuit. These should form part of any electronic engineers arsenal, as discussed here. I just used the breadboard as an extra step

When they arrived I tested them on breadboard first:

I’ve drawn up a nice schematic to show how simple the wiring is:

Remember to cut the tracks on the board between the two supply’s outputs if you’re using strip board.

This time I powered up the circuit using the jump starting trick i mentioned in my previous post and tested the output using a multimeter. The output read 10.5v but there was no load on them so this isn’t unusual. After wiring up one of the panel meters, the output voltage dropped to a more sensible 9.3v

Notice that i have a power resistor (large white block) to load the supply and ensure i get a nice consistent dc source. This is sitting between 5v and ground and is 10Ω. This gets quite hot so until i can give it a heatsink and some airflow, i’m only running the supply for short periods.

Next i soldered the dc-dc modules to some strip board in the layout shown in the schematic above. Remember to cut the tracks between all the outputs of the dc-dc modules, you want those outputs to be completely isolated.

The result is some nice blue:

You can see the circuit in the top right, just below the ATX cable connector. I used a salvaged piece of stripboard from my earlier mishap, hence the additional yellow wire to bridge previous cuts. The breadboard is just to help distribute power and to hold the power resistor.

My next step is making the aluminium box that all this will go into. After that it won’t be long until this project is complete

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