Making A Current Blasting Power Supply With Old ATX Power Supplies

what is Current Blasting? I hear you ask..
Well sometimes when you have a fault with a piece of equipment it's not always easy to track down the issue - it usually comes down to a failed component that has shorted internally - a single failed component of possibly thousands so one method of tracking it down is blasting it with high current (at a low voltage)
It is quite a fun method of trouble shooting because most of the time the failed component explodes off the board, starts smoking or gets very hot.
so what's the best method of doing this? well get a high amp power supply which costs loads of money OR make one out of an old computer power supply.
You have probably seen people make power supplies out of these before for powering their projects which I don't personally think is that great of an idea because of the high current involved but you can use it for that if you wish.

The reason why these things are great for current blasting purposes is because the junked one I have (which is from a very cheap case that had a power supply on it) has a 5volt rail of 27 amps, a 12 volt rail of 13 amps and a 3.3volt rail of 25 amps. which as you can imagine is more than enough.

now for the usual "danger" crap...
I'm sure by now you're used to reading disclaimers and warnings to the point of being desensitized by it and it is easy to ignore these things.
but these things can be very dangerous so you need to take a lot of care when building/hacking these things. They have a lot of capacitors which may retain high energy even when the unit is unplugged. you NEED to make sure they are discharged before you start handling it - that goes for the filter capacitor on the IEC mains input - sometimes they don't have a bleed resistor and can discharge 240 volts (or whatever your local voltage is) into you which I can assure you bloody hurts.

2 Things you must be aware of to use these things

1. in order to switch it on you need to solder the Green wire to Ground (black wire) I suggest
doing this by means of a switch. The green wire will be labelled "PS" or "PSON" on the main PCB

2. some ATX power supplies need a minimum load to function which is around 200mA
to achieve this you must bridge the 5 volt and Ground terminal with a 22Ω resistor.

if you're interested in how this was worked out you can use ohms law
R(resistance)=V(voltage)/I(current) so you type into your Calculator
5 / .200 = 25 so you have the answer 25Ω and you round down to your nearest value which was 22Ω in my case


Anyway here are some pictures, if you have any questions don't hesitate to ask. 

Bare ATX PCB

very cheap supply I found in my shed

I found this on the net some time ago, I'm not sure who it belongs to so if it's yours let me know and I will credit you and your site

Signal Injector / Tracer Stripboard Veroboard Layout

A quick but very useful project. I "designed" (I say designed, it's just a simple astable multivibrator with a basic transistor amplifier) 10 minutes last night and built it this morning basically to help fault find because I'm sick of having to fire up the function generator/scope when I just need a quick tester.
so as usual I will share it with you people.

Maxon OD-880 Overdrive Stripboard Veroboard Layout

Another guitar overdrive (groan) but it's a good type of thing to build when you can't think of original ideas and I am abit stuck at the moment so I thought I would find a schematic of this particular Overdrive and lash up a layout, build it and then post on here for all you people.

The original unit used 3 LM741 op-amps and I was very very tempted to just use a dual and a single op-amp instead but I know people get a bit funny about using alternative IC's and stuff even though it would sound no different, however I specifically laid it out in a way that I could make a little daughter board to use a dual op-amp rather than 2 singles to get better battery life out of the thing.

If you want to experiment some choice component values to alter would be C4, R6, R7, the signal diodes (1N4148) and R9

How To Work Out Parallel Resistance (If You're Completely New To Theory And Don't Get Maths)

First of all you need a Scientific calculator to "play along" I know the one in windows is adequate if you don't have one, I'm not sure what the Mac one is like but I'm sure it will be fine. I personally use a Casio Fx-7000G - it's from the 80's and it's ace - go on eBay and try and find one. I'll put a picture of it below.

Hope this helps anyone who has struggled with it.

Once you Have grasped it you can go test your skills HERE

Ignore the Numbers That's Nothing To Do With This Article

6 Tact Switch Debounce Veroboard Stripboard Layout

This is one of those boring circuits which you need to know when dealing with CMOS circuits and I imagine it would come in useful for those of you using microcontrollers like Arduino/PIC etc.

using this circuit you get a nice clean switch signal from a mechanical switch avoiding miss-switching

2 channels of the switches in action

Guitar FX Regulated Power Supply Stripboard Veroboard Layout

My store bought Effects power supply has been annoying me lately, it's buzzing both from the box and in the guitar signal,it's bad tempered and cuts out and generally just puking up it's entrails, I've been fixing it over and over for years and I finally thought "bugger it I will make a new one" so I did.

It is a very simple build however it is not one to be taken lightly as it involves the mains so you need to take all due care and attention.
Use a metal enclosure and Earth the Chassis, this both adds safety and cuts any stray noise.
Make sure you use a fuse - in my case I used a connector that had a fuse compartment built into it

You will notice that I used a uncommon type of regulator, you can of course substitute this with a LM7809 Regulator, they are pin compatible though I suggest you try and find the ones noted on the stripboard layout.

Be Careful

PWM LED Dimmer Stripboard VeroBoard Layout (Orig. By Dave L. Jones)

Dave Jones did a cool little circuit using a 555 to dim the LEDs on his Mantis microscope. Obviously this little circuit has a lot of uses so I thought I would make a little stripboard layout for it.

There isn't much to say about it as it has already been covered in his video (linked below)

so here you go.

 

1970's wah wah pedal Stripboard Veroboard Layout

Obviously this is not one of mine but one taken from a magazine from 1970. it uses germanium transistors however if you can't find them or they are too expensive just try some general purpose ones like 2N3906 instead of the ones listed.

There are a few odd values that aren't really readily available - just get the ones nearest to them - like in the case of the 50uf capacitor substitute it with a 47uf one and so on.

8 Bit Guitar Fuzz II Effect Stripboard Veroboard Layout

I wanted to make a kind of brutal fuzz pedal for a song I'm working on that needs a really nasty sounding lead bit so I designed this little beast - it was a very very quick circuit so I didn't add any pots or anything to it however I think you will like it (if you like this kind of thing of course)
it also sounds a little bit like the type of Fuzz the Smashing Pumpkins used in siamese dream 

I have uploaded a little sample of it in action HERE

I hope you will add some mods to this - if you do please let me know!
I'm calling it the Quadraspazz Fuzz

Low Battery Indicator ( 9v ) Stripboard Veroboard Layout

I was in the middle of designing a little 9volt battery operated music thing and I thought it would be nice to have a little battery indicator to tell me when it was getting low.
Once I made it up I thought it might be a cool little thing to share on here so you could add it into stuff like guitar FX and so on.

it has 3 states:
1. if the battery is good then the LED doesn't light
2. between 7.5v and 6.4v the LED flashes to warn you it's getting low
3. below 6.4v the LED stays lit

I know there are specific ICs for this purpose however I like making my own "solutions"
Anyway hope you like it.

Behringer UV300 Rate Mod (Slow Down)

I thought I'd take a quick venture into modifying a effects pedal. The one I chose was the Behringer UV300 ( Ultra Vibrato ) I love Behringer gear and in most cases they do a really good job at effects and pretty well everything they put their minds to (see the X3!)
anyway I bought this on a whim cause it was very very cheap, I didn't even bother looking for samples because if I'm honest there is only so many times one can watch people doing out of tune covers of Lucy In The Sky With Diamonds while reviewing Vibrato pedals - also they never turn the rate down to nothing to show you how slow it goes.

as you can probably tell by this post, the "rate" didn't go as slow as I wanted, I like that sort of hypnotic warped record vibrato which this pedal couldn't do however with a little knowledge of how oscillators work and a bit of time probing around with a scope I was able to modify this to go slow enough

In order to slow down the range of the Rate control you basically just have to add capacitors in parallel with C12 and C15 - or you can swap them completely for higher values - the higher you go the slower it is however you need whatever capacitors you add to be very close in value to each other because if one is very different you get an uneven vibrato.
anyway here are the pictures.

if you have any questions - ask!

and you don't need to rehouse behringer pedals, the plastic is very strong - it easily withstands being dropped down stone stairs many times.

solder very quickly otherwise you'll be resoldering SMD stuff!

it's a good idea to do this in order to tailor it to your preference

the part of the circuit I am changing

The Behringer UV300 with its nice new switch

Devils Triangle Drone Synth Stripboard Veroboard Layout

this is a project based largely on the put up or shut up mentality, for quite some time I've been getting annoyed at seeing youtube videos of people pissing about with these "synths" which are basically boxes of 555 timers with a million knobs that make stupid noises that you couldn't ever actually use in music so I thought I would make my own little synth that would get repeatable sounds and be useful in music and what better type of synth? a droner type - basically cause I love bagpipes - I like drones
anyway the circuit itself is quite a simple one basically because I only designed it during the week, all it is really is 3 triangle wave generators configured to operate in the audio range going into a mixer op-amp configuration with the odd filter here and there to soften the waveforms
I've used LM358 op-amps cause they are the cheapest, I'm not too sure if others would work in the same way though they probably will.

why call it the devils triangle - well it has 3 oscillators one of which can oscillate a slightly high pitch range (for melody) it also sounds demonic so the name fit

Hope you enjoy

EDIT: I replaced the level knobs with on/off switches - it makes it so much more versatile being able to silent certain drones 
EDIT: I added a little schematic on how the switches should be wired as it was causing a bit of confusion.

the one I made - with a really shit paint job

Flux Capacitor LED Decoration Stripboard Veroboard Layout

for fans of Back To The Future - or LEDs
I know this isn't exactly like the real thing however that would involve crux tubes and so on and I doubt many people who read my site want to piss about with 10,000 volt supplies. Anyway it's pretty much for my halloween/christmas/bonfire night decoration collection.

as you can see I have included a layout for the actual display board, although it looks like the LEDs maybe abit too spaced out, in practice they wouldn't fit when they are closer together. However should you just want to use the display board I think that each transistor can drive quite a few LEDs (I think the 2N3904s are rated at 100mA)
As it stands the circuit draws roughly 5mA

The last thing I want to mention is the odd value electrolytic (well odd to some) it is 470nf however you can use a none polarized version it just happened that I have both kinds and the electrolytic takes up less space

I also included a little video to show you what it does. HERE

Paul in the
Lab is here to help
Everyone that's into electronics
Always feel free to
Seek my advice
Either using the
Contact button or my email
Lately I am always at the computer because
I am  designing stuff for the site though I did buy a new
Camera recently it's pretty cool. I remember the first thing I built was the
Knight rider LED scanner which I uploaded
To the site a few days ago, remember if you need to know
How to do something
Even if you think it's
Abit of a stupid question just ask, I
Don't mind. We all had to
Start somewhere. 

Fading LEDs / Eyes for Halloween decorations stripboard veroboard layout

The inspiration for this little circuit with Halloween approaching was a post I saw made on this Thrifty Crafty Girl
basically the girl had an idea of putting glow sticks in toilet rolls with eyes cut out to leave in bushes however I thought it would be cool to add an electronic element to it.
so I made a little circuit that will make LEDs fade in and out - they will go in and out of sync and will look pretty dam creepy
Anyway this one quite cheap to make circuit will "power" 4 toilet roll monsters - 2 LEDs per toilet roll or whatever you want to put "eyes" or LEDs in
below is a video of it in action

Paul in the
Lab is here to help
Everyone that's into electronics
Always feel free to
Seek my advice
Either using the
Contact button or my email
Lately I am always at the computer because
I am  designing stuff for the site though I did buy a new
Camera recently it's pretty cool. I remember the first thing I built was the
Knight rider LED scanner which I uploaded
To the site a few days ago, remember if you need to know
How to do something
Even if you think it's
Abit of a stupid question just ask, I
Don't mind. We all had to
Start somewhere. 

Voice Bandwidth Filter for podcasts / youtube veroboard stripboard layout

This idea came about when someone was tweeting on twitter that they were having problems with rumble noise and high pitch squealing from some air conditioner unit. So I thought I would make a filter for people to combat such problems, basically this thing attenuates anything below 300Hz and anything higher than 3KHz which is pretty much everything outside of the vocal range.
This could be a useful thing to combine with the high quality Microphone Preamp I designed some time ago located HERE

It's been a while since I posted a project because as you (may) know I build up things before I post them so I know they work however I've had bugger all money to buy stripboard, I actually had to de-solder an old project to get enough to prove this one so if anyone can help me out with some stripboard I'd be most grateful!

Paul in the
Lab is here to help
Everyone into electronics
All ways feel free to
Seek my advice
Either using the
Contact button or my email
Lately I am always at the computer because
I am always designing stuff though I did buy a new
Camera recently, I remember the first thing I built was the
Knight rider LED scanner which I only
Added a few days ago, anyway I
Digress, hope you enjoy my
Site

anyway here is the filter

Knight Rider Kitt / Cylon LED Sequencer Stripboard Veroboard Layout

This is a cool little project I've been meaning to do for a long time. One which was so simple I kept putting it off.
Essentially this is a 8Hz (ish) squarewave generator attached to a decade counter - it counts upwards displaying each count on the next LED however the outputs are wired in such a way that instead of just going upwards it goes back downwards. it should be obvious when you look at the schematic how the thing works.

Anyway as the name suggests the LEDS go back and forth like the eye things on Cylons from battlestar galactica or the front panel on the car from knightrider. my older brother drives a taxi so I plan on using this to drive relays to big lamps and attach it to his car when he's next away.

This circuit is very useful outside of replicating old TV show LED things, you can use it to sequence pretty much anything using relays or even digital circuits and you don't have to use the 555 to do it automatically, you can replace that with a push switch circuit to the CD4017 Clock pin (14) and control a pedalboard for example
or maybe even make your house seem haunted by using it to remotely control appliances. I will include a simple Relay Driver below.

 

To use the CD4017 to drive a relay

Mosquito Repellent Stripboard Veroboard Layout

I'm pretty ill at the moment and I didn't want to really get up let alone make a circuit however the reason I am ill is because of bastard mosquitos - you see they bite you and your body reacts to the bites as it would a virus and with an illness the actual feeling of being ill is your body attacking the illness. in most people this reaction lasts a very short time and you don't notice it however with me any illness I get prolonged reactions, I always have which is why I feel really ill right now.
So in order to stop it happening again I thought I would make an electronic mosquito repellent

it mimics the sound the pregnant female mosquito makes which warns others to stay away.

RIP Hans Camenzind

sadly, the inventor of the 555 timer IC passed today

Dual Tracking Power Supply Stripboard Veroboard Layout

another project born of necessity (ie I blew my other one up) This is a 1.5Amp dual polarity power supply (adjustable)

This may look like a waste of stripboard however once you see how big the 1000u caps are you will realize that you need the room.