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richms

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#1010525 21-Mar-2014 12:10

This guy seems to have a reasonable reviews on dirt cheap ebay purchases - https://www.youtube.com/user/julius256

The power supply he uses for the LEDs just takes in 12v give or take and is current and voltage controlled.

Richard rich.ms

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pbgben

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#1010537 21-Mar-2014 12:22

Mark: Well good luck with that .. personally I think it's stupid to recommend to an electronics newbie to go and start playing with a PC power supply, and I just hope that the people behind the usernames saying it's OK don't ever do any work for me.

While you are at it, under your sink there are all sorts of chemicals, why not go mix them up and see what happens, I'm sure it'll be just fine!

What would you recommend? Please keep in mind that I don't have an unlimited budget, its rather small.

$5USD 1GB RAM, 10GB SSD VPS in SYD

ubergeeknz

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#1010578 21-Mar-2014 13:33

pbgben:
Mark: Well good luck with that .. personally I think it's stupid to recommend to an electronics newbie to go and start playing with a PC power supply, and I just hope that the people behind the usernames saying it's OK don't ever do any work for me.

While you are at it, under your sink there are all sorts of chemicals, why not go mix them up and see what happens, I'm sure it'll be just fine!

What would you recommend? Please keep in mind that I don't have an unlimited budget, its rather small.

9v battery + 7805 ;)

sleemanj

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#1010654 21-Mar-2014 15:23

ubergeeknz:
9v battery + 7805 ;)

Cheap but not that flexible :-)

I'm about as cheap and bodgy as it can get, and most of the time I use this contraption I put together:

Excuse the shameless self linking, but it consists of an LM2577 SEPIC converter with a voltmeter on the output and a 5.5/2.1 DC socket for the input, replaced the trimpot on the 2577 board with a large multiturn potentiometer (actually I added the meter and pot later, for a while I just used a screwdriver to change the trimpot and a multimeter to set the voltage).

Power it from any voltage source I have handy, usually either some AA cells in a holder or one of the many DC power bricks I have in junk bins all over the place if I need more current, also has binding posts on the back for input power if necessary.

Because it's a SEPIC, doesn't matter what the input voltage is, the output voltage can be dialled higher or lower than it as I need.

I put it in a box made out of an old event sign (5mm coreflute) and hot glue, great stuff for quickly making a strong and virtually free project box :-)

---
James Sleeman
I sell lots of stuff for electronic enthusiasts...

zaptor

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#1010657 21-Mar-2014 15:23

pbgben: Please keep in mind that I don't have an unlimited budget, its rather small.

Hmmm... electrical circuits/equipment/devices aren't necessarily the "cheapest" things to make mistakes on.

I mean, if you haven't fried and/or blown up a digital/analog component, mother/daughter board, PSU etc, then you probably haven't been fiddling long enough. Even with all the current protection built into stuff these days they still fry.

Mark makes a fair point.

Have you done a primer on basic electrical safety. Wouldn't hurt to do an intro on analog electronics either?

Aredwood

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#1010920 22-Mar-2014 02:23

Don't know why there is always at least 1 post with a whole lot of FUD whenever it is suggested that a computer power supply is used to run something other than a computer. The ATX power supply standard requires voltage monitoring on all outputs. Over voltage on all and under voltage on all except the 12V rail. But in reality due to the way most supplies are built. (a transformer with different tappings for each voltage) If you try drawing a large current on the 12V rail without drawing much from the 5V and 3.3V rails. The voltage will increase enough on the 5V or 3.3V rail to activate the protection circuitry. Try running some 12V halogen lamps or a motor from a Computer power supply. The startup loads will often trip the protection circuitry. Meaning you are doing well if you manage to even draw 2/3 of the rated current from the 12V rail.

And a computer power supply is far safer to use than a car battery. Reason being a car battery will easily supply over 1000A in a direct short. Therefore it can easily start fires or heat wires or tools to red heat. And they can also explode if short circuited.

When I started into electronics, A car battery was my first high current power source. When I think back to some of the early circuits I made, No fusing ect I was lucky not to start a fire. Although buying a proper lab power supply is all well and good. Buying one that can supply more than a couple of amps or so quickly becomes expensive. I also made some power supplies using transformers I had removed from old amplifiers. Using a computer PSU is far better than trying to make your own transformer supply (which most likely you will need to do some mains wiring to do so). When the OP finds they need more current than what a wall wart supply can provide.

As for the one that caused the electrocution. It would have had to not been earthed. Used without RCD protection, plus whatever fault caused the mains to conduct to its metal case. Unless they removed the covers from the supply meaning it's circuit board was exposed.

Mark

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#1011153 22-Mar-2014 21:20

Aredwood: Don't know why there is always at least 1 post with a whole lot of FUD whenever it is suggested that a computer power supply is used to run something other than a computer.

As for the one that caused the electrocution. It would have had to not been earthed. Used without RCD protection, plus whatever fault caused the mains to conduct to its metal case. Unless they removed the covers from the supply meaning it's circuit board was exposed.

You don't seem to get across what I'm trying to say .. "It is a DUMB idea to suggest to a NEWBIE electronics hobbits that they use a PC power supply." the reason is that they are a NEWBIE!!! AS in they are new to the hobby, may not know how all the volts, amps, rcb and multitude of other terms all tie together, so suggesting they play around with something plugged into the household supply is just mind numbingly stoopid! :-(

I may not be a qualified electrician and know only enough to be dangerous, but I do know when I see dumb advise when I see it.

As to the electrocution ... it was 18 years ago and me grabbing a PSU on a table to move it out my way, not being an electrician (and 500% dumber/less experienced back then) I had no way to diagnose at the time if it was earthed or not or even if it should be .. to me it was an object in my way. And yes it got reported and all the other myriad of HR and health and safety things ensued. But it is a VERY good example of why PC power supplies are not great to have laying around.

Stu

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#1011157 22-Mar-2014 21:42

18 years ago, it would possibly have been an AT PSU, not ATX. A mechanical 230V switch on a fly lead coming out of the PSU case meant it was quite a bit more dangerous than the ATX units, and the chance of receiving a zap from it if it was connected to the mains while sitting on a bench would be much higher.

blakamin

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#1011158 22-Mar-2014 21:49

Only time I've ever had an issue with a PC power supply was 1997... I had the case off it, plugged it in and ZOOM! clenched everything! Burnt a hole in my foot, that was grounded, and my thumb.
Pulled away far enough that it unplugged.

Only thing I would say here is to never open a power supply because you might touch the mains rail.

I've been using them for years to power 5v and 12v gear since, but I'll never open another one!

Stu

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#1011160 22-Mar-2014 21:57

Absolutely. Unless you're a sparky, leave the PSU case closed. End of story.

richms

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#1011174 22-Mar-2014 22:11

And plug it into a RCD if the house is old and doesnt have one already, and if it does have one, when did you last test it?

Richard rich.ms

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