12v adapter for lights

[Stormin Mormon]

I remember reading that the PC power supplies have some kind of power saving sleep mode. You need to plug in an old drive, in order to get the 12 volts to work. Anyone know for sure?

[The Daring Dufas]

That would be a function of the motherboard and it's BIOS program. The motherboard, if so equipped, can control the fan speed of a compliant power supply and when the computer is off but still plugged into line current, there is 5 volts DC coming from the power supply for the quiescent state of the mother board. Some motherboards have wakeup modes that can be triggered by a dial up modem receiving a call, a network card if made for that function, USB port activity and keyboard input. None of the PC power supplies that I've taken apart have had any microcontrollers or memory. It wouldn't surprise me if some expensive server power supplies had brains but I've never come across one that has. Here is a link with some information on APM, Advanced Power Management.

TDD

[clare]

On an old PC/AT (not atx) supply all you need is a load on the 12 volt, I believe. (could be the 5, but I'mm 99% sure it is the 12 that it regulates from)

[Jim Yanik]

"Stormin Mormon" wrote in news:gp4jmi$f9$ [e-mail]:

switching supplies need a minimum load to regulate properly. And PC supplies regulate off the +5 volt line.

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

No,it's the +5V;after all,that is what the ICs use,and they don't tolerate over/under voltages well.

[clare]

So you pop a small power resistor on the +5 to regulate, and you are on your way.

[gfretwell]

I have a stack of old PC supplies and most of them will power up and be stable with nothing plugged into them. I know the old AT supply needed a load but the newer ones must have some internal load to regulate against.

[clare]

The ATX may not need the 5 volt load but are not as reliable, on the whole.

[JIMMIE]

Its both, the regulator chip monitors both the 12V and 5 volt output. They can be easily modified to monitor just one voltage or to change the output voltage somewhat. By changing the value of a resistor you can "fool" the regulator into "thinking" its putting out more or less voltage than it really is thereby increase / decrease the output voltage. Jimmie

[JIMMIE]

Might not be a + if you are selling your house with one installed.

Jimmie

[SMS]

- what about the fire hazard: should I replace the whole lighting

Remember, the track lights are 12 volts AC, not DC. Running them on DC will work, but the wiring of the lights may not be designed for DC.

Probably it's cheaper to buy another set of lights from Ikea and use the transformer from it.

You can buy a transformer at a place like "

". Maybe Home Depot or Lowe's sells them as well.

In the olden days you could buy a 12.6V filament transformer for a few bucks, but no more.

Again, it's a bad idea to buy a 110VAC to 12VDC power adapter for track lights.

[clare]

Changing the load resistance should NOT change the output voltage. That's the idea of regulation. You just need a load on the bus to stabilize it.

[clare]

They have all the certification you might ever want so what's the problem? Just do the installation so it looks like it was planned to use that power supply.

[clare]

> - what about the fire hazard: should I replace the whole lighting

Actually the wiring will make no difference - and as long as you are switching the high voltage (ac) you don't need to warry about DC rated switches. The lamps will "like" regulated DC better than sloppy AC too.

And have the same cheap crap fail in the same manner in the same short time??? What's wrong with this picture???

It's a waste of money if it costs you more than an adequate AC transformer - but even a GOOD NEW ATX power supply of adequate capacity can be bought for under $30 - used PC/AT supplies are a dime a dozen.

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

he's not talking about LOAD resistors,but the resistive divider inside the PS that sets the output voltage. But changing the output V of one of the output voltages will also change some of the other unregulated supplies. The supplies track each other,unless they have a separate regulator circuit.

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

it's essentially a custom mod that is unsupported;nobody will service it.Nobody will accept responsibility for such a mod.

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

Fine if you want a KLUDGE. the next owner will probably not know what to do with it,when a problem occurs with it.

[JIMMIE]

.com:

Excuse me, where did I say anything about changing the value of a "load" resistor?

Jimmie

[gfretwell]

How did we get from fixing a cheap light to selling the house?

[clare]

My FIRST mention of a resistor was a load resistor. I never mentioned getting inside the box at all.