|
Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
|
Thread Tools |
17th Mar 2018, 2:43 pm | #1 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
|
Useful project case from discarded PC SMPS
I found a junked PC switched-mode power supply in the street and have repurposed the case. I thought this might be of interest to others looking for simple, ready-made project cases.
The application is a simple square wave generator with a class B output driver using PNP and NPN transistors configured as emitter followers. I can produce 2A pulses with perfect waveforms and fast rise-times, variable from TTL level to 20V P-P. I need this to 1) calibrate a home-made current transformer and associated over-current detection board (logic) which is a key component of my major ongoing project. 2) test the home-made gate transformers for my major project There are several benefits in using the case. The following come already fitted:
These pre-fitted components save a few quid and quite a lot of labour in cutting out small shapes. As you can see, there is plenty of room to add another output stage. If that stage were to need heat-sinking and cooling, it would find itself handily next to the 12V fan. The fan shown is not connected. The case also contains RF at the design frequency, which is approx 80-200KHz. The lid is easily removed. It is fiddlier to work with the two end panels of the lid than to remove one and fit an alternative (cable runs to potentiometers etc would need to be longer). Accordingly, I replaced one end with some plain FR4 board. It's not stunningly beautiful, and the case I found had a dent in it - (from where someone was perhaps trying to salvage bits?) - but it serves my purpose - housing a piece of bespoke test equipment that will only be used sporadically. It could easily be made more attractive by knocking up a simple FR4 copper-clad board top instead of the grey steel that it comes with. It was worth going to the effort of laying-out and housing the electronics like this, as the rise time of the active devices is less than 80nS. Hence poor grounding/layout easily produces 2-5% overshoot on the square wave output, which is unacceptable. As you can see from the 'scope trace, the waveform is perfectly clean. This is a light little project but it means a lot to me - given my current limitations - and it takes me one step closer to achieving my major project.
__________________
Al Last edited by Al (astral highway); 17th Mar 2018 at 2:56 pm. |
17th Mar 2018, 3:04 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
|
Re: Useful project case from discarded PC SMPS
Cunning! Like you say, the 'pre-installed' features cut down on the time taken when building something new into the chassis.
Someone I know has a 100-watt-per-channel amplifier built into an old 1990s PC PSU case; the fan is very much needed...! |
17th Mar 2018, 3:23 pm | #3 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
|
Re: Useful project case from discarded PC SMPS
Ahah, yes! Class A?
__________________
Al |
17th Mar 2018, 3:39 pm | #4 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
|
Re: Useful project case from discarded PC SMPS
No, some Chinese Class B disco-amplifier modules and a SMPS giving +/-70V. He's the kind who only ever has it turned up to '11' hence the need for the cooling!
|
18th Mar 2018, 11:17 am | #5 | |
Nonode
Join Date: Apr 2012
Location: Worcestershire, UK.
Posts: 2,052
|
Re: Useful project case from discarded PC SMPS
Quote:
|
|
18th Mar 2018, 12:23 pm | #6 |
Dekatron
Join Date: Jun 2013
Location: East Sussex, UK.
Posts: 3,326
|
Re: Useful project case from discarded PC SMPS
Also useful is the array of good cables in a variety of colours from the smps.
|
18th Mar 2018, 12:28 pm | #7 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
|
Re: Useful project case from discarded PC SMPS
Thank you! I now have two or three more junked cases in stock. I went to the PC repair shop and asked the owner if he had any broken units. I told him why and he was initially very suspicious so that I would fix them and sell them for a huge profit on EBay!
We swapped for a few quid in the end. There are also good heatsinks in the units, a couple of high pulse capability poly caps which cost a few quid each new and loads of multi-way connectors. The fans are usually polarised and often suck air instead of blowing it. A pressure gradient is achieved by having a snug case with just the right number of slots cut out.
__________________
Al |
18th Mar 2018, 5:47 pm | #8 |
Nonode
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 2,038
|
Re: Useful project case from discarded PC SMPS
Excellent Al. I once built a 4m (70 MHz) amateur band transceiver into a PC PSU case, and with the addition of a brushed aluminium front panel it looked pretty good.
It's worth keeping an eye open for PC CD drive cases too for 'slimline' projects.
__________________
Andy G1HBE. |
18th Mar 2018, 7:19 pm | #9 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,108
|
Re: Useful project case from discarded PC SMPS
The aluminium enclosure of the Roland Edirol firewire audio capture FA66 (what a mouthful) looks like it has potential for a small project box. I was given a broken one and held onto the case-once either end is unscrewed the two boards can be slid out and you are left with a neat anodised open ended case with slots for insertion of boards of your own specification. The end panels have multiple piercings for switches, pots and sockets, but they are such a simple shape that making new ones would not be a challenge.
|
18th Mar 2018, 8:14 pm | #10 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
|
Re: Useful project case from discarded PC SMPS
Andy and The Phillpott, great tips, thank you both!
__________________
Al |
19th Mar 2018, 12:54 am | #11 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
|
Re: Useful project case from discarded PC SMPS
Old set top boxes are good too and some of them even have a power supply in them.
I have a part built project in the case from an old coax router that came with a laminated transformer power supply and C13 input. It is a cast box. |
19th Mar 2018, 10:47 am | #12 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
|
Re: Useful project case from discarded PC SMPS
It's amazing what you can repurpose: in the past I've used the extruded-aluminium cases of portable hard-drives: they often have a 'figure-of-8' mains power-socket and USB socket already fitted on the end plate and a small 5V/12V SMPS inside. I've got one here with a TBA810 audio-amp built into it.
|
19th Mar 2018, 5:54 pm | #13 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,273
|
Re: Useful project case from discarded PC SMPS
I once turned a Rediffusion set top UHF downconverter into a christmas tree light sequencer, in the days before you could buy fancy lights, of course.
__________________
Kevin |
19th Mar 2018, 6:03 pm | #14 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
|
Re: Useful project case from discarded PC SMPS
Great ideas and imagination, all!
I love it. In a world where lots of consumer electronics are no longer recovered once they're trashed after 3 to five years, very often, it's nice to know that a few of us are giving things a second life.
__________________
Al |
19th Mar 2018, 11:42 pm | #15 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
|
Re: Useful project case from discarded PC SMPS
I have just cadged a nice IP65 ABS box from the utility engineer whom was changing the smart meter for the gas. It used to dangle in the dust under the first generation smart gas meter.
When I asked the engineer if I could have it for recycling in house he picked up a pair of side cutters, snipped it off and handed it to me It is about the size of a deep single 13 amp socket. |
23rd Mar 2018, 4:36 pm | #16 |
Tetrode
Join Date: Dec 2017
Location: York, North Yorkshire, UK.
Posts: 65
|
Re: Useful project case from discarded PC SMPS
I know its been done before, but I was doing this many years ago. Putting clock mechanisms in things. B+O turntable outer platters are popular on ebay. Same with old CDs and 7" singles.
I prefer to use spool to spool spools. The metal ones look really good. I have a Sony spool with 12 circles impressed in. Perfect . I have used a Mk4 Ford Zodiac Hub cab too. Last week I bought a 60s electric clock off the bay for 3 quid. The mechanism is totally seized beyond repair, and I wouldn't want to leave it plugged into the mains if I was not around to keep an eye on it, so its getting a battery powered unit put inside. Project cost £6.00 but tinkering time and smiles invaluable . Brett.
__________________
BVWS Memeber |