I am looking for a 3-4 amp 10 v DC power supply in either wall wort form, or alarm AC transformer form. I can't seem to find one, and would like to not have to make my own.

Mike

Wow, thats a strange requirement......

a 12v Supply should work just fine.

A Laptop charger would be a good economical choice offhand. Lots of options on those....

Meanwell P40 Series.... 9 or 12v options....

Whats the APplication?

I 2nd that. What's the app?

I have five 3x16 cable routers that use a 10v 200ma power supply. I have gone through about 6 power supplies in a year. We contacted the manufacturer, and the admitted they had a problem and redisigned it. Of course they didn't last either. I am looking for a solution that would allow me to power all of the routers with a decent amperage. Also, a little more heavy duty. I could use a 12v PS for an alarm system, hopping that the routers load would reduce the voltage close to 10v, but would like something a little better.

Mike

Rat Shack use to have a nice 3 amp 12V regulated supply for about $40. If they still have it, is has an internally adjustable regulator for dialing in the voltage. You may get it down to about 11V without any modification but anyone with electronics knowledge could easily modify the regulator down to 10V. It's a solid supply but just one option.

Use an Altronix SMP5. It is a 6/12/24Vdc power supply with a 4A output rating. If you don't need exactly one of those voltages it has an adjustable pot to change the voltage to exactly what you want. You can get it at any security distribution shop or online.

http://www.skycraftsurplus.com/

Call these guys they have everything.
Honest.

Another option: diodes have a 0.6v forward voltage drop, so you can stack 3 or 4 in series to drop a 12v supply to the desired voltage level.

Be sure and check your chosen supply with a voltmeter before installing. Lots of cheap supplies give you a "nominal" 12v or whatever. We had a 12v supply at the shop that put out 15v. Wall warts are pretty variable as well. Often you have to "load" the supply, or hook it to something that pulls current, to get its accurate reading.

Larry's comment about stacking diodes is a good solution - make sure your diodes are rated at 5 to 10 amps though for a margin of safety.

I like the laptop supply solution. A computer store will probably have an assortment of scrap laptops with good power supplies, or ebay...

If you do this, beware the following issues:

You'll need to get diodes rated for this current.
4 diodes at 0.6V each, is 2.4V * 4A = 9.6Watts. The diodes will need to have heat sinks, and you'll need to limit what these come into contact with, as the heat sinks will also get hot.

If you can find a Switch Mode Power Supply with an internal voltage adjustment, and adjust the supply yourself, this gets around all these issues.

Note that many of the wall transformers are poorly regulated. You may find that the equipment will function fine on 12V nominal power, and the equipment manufacturer specs 10V, because the supply sags to 10V at full power (UL has the manufacturer spec at full power).

If you have a still functioning transformer, look at the output voltage with a voltmeter and no load. If the voltage is 12V or over, you should be fine with a 12V supply.

My reasoning is that the device manufacturer ends up sizing the power supply input for the worst case positive input voltage, which is usually the no load condition. So what ever voltage the original supply goes up to, you'll be fine with supplying that voltage yourself.

Your best bet would be one of those adjustable regulated power supplies.


Switch mode supplies are nice because they are smaller and more efficient, which can mean cooler, than brute force supplies (see my note at the end), but there is no reason one would have to find a switch mode supply. Any supply with an asjutment will do. I guess maybe switchers are more likely to have adjustments, though, as their electronics are more complicated.


Larry, you beat me to it. I would say 0.7 volts, though, but whatever; a few diodes in series with the power supply should bring you down to 10ish volts.

And yes, you do have to consider the heat these will be putting out, and be sure the diodes are rated above the current they will be passing.

The comments about 12 volt supplies putting out 15 are on the mark, especially wall warts. Those supplies are unregulated and put out the correct voltage when their rated current is being drawn. When less current is drawn, the voltage goes up. For this very reason, for instance, the original Xantech power transformer was a 9 volt unregulated supply that would sit around 12 volts when loaded. They told you never to use 12 volt supplies (for their products rated at 12 volts) because then people would use unregulated supplies that would sit around 15 volts and would lock up Xantech equipment.

If anyone wants more facts on why regulated, or why unregulated go up in voltage, respond here or email me and I will carry on....

Okay, how about an ugly, oversized, noisy, bulky solution?

Get two computer power supplies and wire the 5-volt sections in series. Warning: don't let the two chassis touch each other.

Larry, that might not work. Chances are good that the minus voltage for each supply is connected to the chassis, which is why you don't want them to touch, and that they are also connected to the third prong of the power cord, so plugging them in AT ALL with the outputs stacked will short the chassis together.