Quick electrical question...and a few more

[ninjasquirrel]

Hey guys I want to cool my bartop project with 4 pc fans rated at 12v each-Each pulls 0.1 amps  I have an old wall wart rated at 9v but actually outputs @14 volts when tested with the multi-meter with no load. When I wire tied all the grounds and leads together and checked the voltage, it was reading @7ish volts (i'm pretty sure, need to check again)
I also have the linx LED lighting that groovy gamer gear sells it's rated at 12v also. Can the fans and lights be wired to the wall wart directly and everything be happy? Or does it need to be regulated better? I have VERY little room inside the bartop so I need a very small solution to fit inside it.

question #2
I also have a pc speaker system that i'm using. The power supply on it is a pretty large brick and is rated at 14v output. What are my options to tie this thing into the same system as fans and lights? I don't have room for a pc power supply, so I like the idea of the small wall warts, but even the speaker brick is almost too large!
Thanks

[scream1973]

You have to look at the total amperage being drawn.

Typically if you supply less voltage to a device like a fan you will just get slower rotation but everythign will still function properly.. However LEDS can be very particular about what you are feeding them.
Your best bet is to take a 12 volt regulated feed off your pc power supply. Or barring that get a regulated wall wart.

[DillonFoulds]

+1 for a PC power supply. If you don't think you can afford the space for a full sized atx power supply, what about scavenging old computers for an mATX supply? Or perhaps find an ultra small form factor (usff) dell computer. They typically have proprietary supplies with a much smaller footprint, but the same standard of color-coding the output wiring.

[lilshawn]

Or barring that get a regulated wall wart.

an SMPS power supply can supply 2 or more amps (even over 5 amps is available) and be 1/5th the size of a conventional wall wart of similar output...this one is about 2x2x5 inches...could be tucked out of the way someplace




http://www.ravirajtech.com/smps_power_supply_adapters_india.htm

[Donkbaca]

you could get one of these:
http://cgi.ebay.com/MOLEX-SATA-HDD-Bluray-12V-5V-DC-AC-Power-Adapter-9B-/350240383232?pt=PCA_UPS&hash=item518bf42100

[lilshawn]

you could get one of these:
http://cgi.ebay.com/MOLEX-SATA-HDD-Bluray-12V-5V-DC-AC-Power-Adapter-9B-/350240383232?pt=PCA_UPS&hash=item518bf42100

that's a good price!

[ninjasquirrel]

thanks for the suggestions, that smps supply looks like it would be perfect. I couldn't open the ebay link for some reason, it kept freezing my browser but I should be able to find one. As far as the 14v needed to power the amp/speaker system, any idea what i could do there? Could I still use the 12v or would the underpowered supply mess up the system?

[lilshawn]

How much current does your amp need?

[danny_galaga]

FOUR fans for a bartop?

[ninjasquirrel]

As far as the current, I couldn't find exact specifics on the speakers/amp pull but surprisingly I did find out that the input voltage could be a range of 12-14v so I think I should be just fine with that smps supply...as long as it doesn't overload it with the fans/lights/amp/speaker all pulling from it or burn it up.

Danny_galaga-lol...I know seems overkill but I have very little room and am worried about overheating with all the electronics inside so 2 input fans and 2 output fans-
http://forum.arcadecontrols.com/index.php?topic=101426.0

[lilshawn]

Easy way to find out the current draw... What's the amp fused for? 5 amp fuse? 10 amp fuse? 30, 60 amp?

It will give you a worst case scenario for draw, but bank on at least 1/2 the fused rate.

My car amp is fused 50 amps, but will consistently draw 35 when driven hard. So they bump it up a bit to be sure. Its gonna blow them if the output gets dead shorted anyways.

[danny_galaga]

As far as the current, I couldn't find exact specifics on the speakers/amp pull but surprisingly I did find out that the input voltage could be a range of 12-14v so I think I should be just fine with that smps supply...as long as it doesn't overload it with the fans/lights/amp/speaker all pulling from it or burn it up.

Danny_galaga-lol...I know seems overkill but I have very little room and am worried about overheating with all the electronics inside so 2 input fans and 2 output fans-
http://forum.arcadecontrols.com/index.php?topic=101426.0

oh! Now I get it! Very nice work (",)

[Blanka]

My car amp is fused 50 amps, but will consistently draw 35 when driven hard.

No digital amp? 420 watt is ridiculous, you can drive a small concert with that. So you either have a small feet-heater in your car, you are deaf, or you use the lowest of the lowest db/watt speakers you could find.
I have a battery-powered T-amp, that does 15 watt max, yet on my 90db/watt 2 tower-speakers they fill up the whole living room with clear 100+ dB.

[Blanka]

On Topic:
What system is in the bartop?
A hacked laptop can be vented passively with ease.
And for the bricks: they are on purpose 1-2m from the unit they feed. A built in PSU is shielded, these plastic bricks are often not inside the gadgets because of EM interference. It will probably work, but it might bring troubles.

[Cenobyte]

I think 4 fans is overkill too. I recently built a Weecade (with TFT, which gives off less heat than a conventional monitor) and all I have is one fan on the CPU. I had the thing running for a couple of evenings and everything stayed nice & cool.

[ninjasquirrel]

So i've decased the 14v power brick and I'm going to try and use it to power the 4 fans, led strip lighting and speaker system. Here's the specs for the components:
1 fan- 0.1 amps  12v
led strip- 400 ma   12v
speaker amp/sub - 12-14v amps?

the brick is rated at 14v  1.2 amps
will I be ok to run everything straight off the brick or do i need another solution such as a voltage regulator or diode etc? I don't know much about regulating the drop in voltage at all so you will have to hold my hand on the explanations 

[MonMotha]

Most likely, the 12V components will be fine running off of 14V.  The fan will run a little faster, and the LEDs will be brighter.  It is remotely possible that immediate damage will occur, and the lifespan of both components will probably be reduced.

The LEDs have a very static current draw, so the simplest thing to do would be to use a resistor to drop the voltage down.  A 5 ohm resistor will drop 2V to give you 14-2=12V for the LEDs at 400mA.  You need a fairly hefty 1.5-2W resistor for this purpose.

The fan is a little tougher since the startup current is much higher than the "run" current.  I probably wouldn't even worry about it (I'm running a 12V cooling fan off ~14V right now - it's doing OK so far), but a ~20 ohm resistor will drop it back down to 12V at the "run" current of 0.1A.  This will probably make it start up a lot slower and could cause reliability problems as well.  You could try a 7812 type voltage regulator.  2V is probably enough voltage difference.  It will only dissipate about 1/4W, so it probably won't need a heatsink.

You could also run the LED strip off the 7812, but that would substantially increase the power it dissipates probably necessitating a heatsink.  Then again, finding said heatsink may be easier than the 2W resistor.

As to whether your supply is big enough; it's tough to say.  The amp is the biggest variable in this equation, and you don't know it's draw.  If it's a smallish amp, you're probably fine.  You've got almost 10W to spare once your fan and LEDs are taken into consideration.

If you already have a conventional PC (not a laptop) in the case, just use the 12V rail on it.  It'll have more than enough capacity for this.

[lilshawn]

The amp is the biggest variable in this equation, and you don't know it's draw.

the load is going to vary anyways depending on what's currently being played... simple quiet background music may only draw a small amount, but big huge explosions and bass hits from shooting a gun may cause the amp to draw 5 times that.

example: i have currently re-purposed the amplifier from a time crisis 2 cab... it's 6 channels (tweets, mids and subs, separate amps for sub), 12 volts and draws 664 milliamps (0.664 amps) at idle. when playing big huge explosions and bass tones, the draw is 1848 milliamps. (about 2 amps)

No digital amp? 420 watt is ridiculous, you can drive a small concert with that. So you either have a small feet-heater in your car, you are deaf, or you use the lowest of the lowest db/watt speakers you could find.
I have a battery-powered T-amp, that does 15 watt max, yet on my 90db/watt 2 tower-speakers they fill up the whole living room with clear 100+ dB.

actually it's "600" so theys advertise i'd acually say it's 300, and it's driving a dual 12 inch 6th order bandpass sub enclosure so it's extremely efficient... i don't actually need all the power the amp has to offer. the speakers and my ears are basically the limit.

[ninjasquirrel]

Ok after considering my options, I have one more to run by you guys dealing with the power. From the beginning I thought about using the 12v rail coming from the pc supply itself but thought it wouldn't be able to handle all the load effectively. Here is a pic of the external supply brick I'll be using to power the all the components...just in case you wanted to know, the pc is a gateway 2000 profile 5 (an all in one lcd monitor/pc):



Are the 15 amps (180 watts right?) enough to run the sata drive, lcd, and misc pc components, plus the fans, leds, and speakers when a game gets intense with big bass etc?

I only have one single molex coming off the motherboard, because it's an external supply:



So I could I simply cut the red wire and tie it into a terminal block, then daisy chain all my components into the block?

Another question...as far as controlling the sound volume, I have the original cable going between the pc and amp/sub and it had a stock volume control. I've bought the vol control from radio shack ( in the picture) but i think the radio shack control is mono right? The cable seems to be stereo...am I correct on this one? Is there anyway to use that vol control, or would it be just mono?

[lilshawn]

could I simply cut the red wire and tie it into a terminal block, then daisy chain all my components into the block?

red is 5 volts, yellow is 12 volts.

I thought about using the 12v rail coming from the pc supply itself but thought it wouldn't be able to handle all the load effectively.

your issue is going to be that the brick is designed to run the computer and lcd an other whatnots... so i believe you will be fine with your fans and stuff added to it, but the supply wasn't spec'd over what the original computer configuration needed by much. (maybe 10%)

you are going to have to find another supply to run your amp. it's going to be too much. it will push it over the edge. if it does work, it will run hot, and you chance pushing the 12 volt down too far and causing reboots, crashes etc. it would be best to isolate the wildly variable load of the amplifier from the computer supply and save the nice clean power for the computer.

the radio shack control is mono right?

yes it's mono...you could tie the left and right channels together to form one single mono channel...it's a bad way of doing it and there can be some drawbacks, but it's cheap and dirty easy fix if a stereo pot is not available..