Computer power supply for TT 12 volt

Anything to do with mechanical, construction etc

Computer power supply for TT 12 volt

Postby jamesm » Sat Mar 29, 2008 11:29 am

I have received a couple of question on the computer power supply I use for my 12 volt power supply in my TT. First I am a hack and make no claim that this is the correct or even an acceptable way to to this. Of course no one should do this unless you know what you are doing and have all the proper tools and knowledge....So it you burn down your house or TT or worst :o Don't say I didn't say not to do this! Ok that was my disclaimer
I have seen on the web that some people have used computer power supplies to convert 120 volt to 12 volt. So I thought I would give it a try. I had some old computer laying around, but a friend of mine had one out of his computer and gave it to me. I found a site on the web that explained how to determine which power supply you had and how to wire it. I did find it was missing a minor but important step, which I will point out in the pics. The power supplies are solid state so the should hold up in the TT with no problems plus they put out a very clean 12 volts.

Mind you I am no computer guru. I just like to make stuff and use what I have on hand.

Here is a link to the website that explains the power supplies.

http://www.marcee.org/Articles/PCPowerSupply.htm

Here is my finished power supply. You can see the positive and negitive posts and a led light I put on it to show when it is on. I got the led light from an old computer. The posts are just 10/32 bolts run thru a grommet with a nut to hold it in place and another nut to use to attach the wires to it.
Image

Here are a few inside shots of the power supply. I drilled holes in the case for the bolts and led light. I cut all the wires down close to the board that I would not use and cut the ones I would use a little closer. The article says you can put some hot glue over the cut ends...but I didn't because they are cut so short they can't move and touch anything else..and it is low voltage.

I didn't go back and read the article but I think it left out a couple of wire connections to make the power supply work properly. The power supply has to have some sort of signal that says to turn on and another called "power good". (Don't ask cause I don't know...like I said I am a hack :? ) (Oh yea I have a volt meter so I could confirm the voltage of the wires.)

I soldered the green wire (power on) to a red wire (+5 volts). I then soldered the gray wire to another +5 volt wire. I think this is the power good wire. I then took four common wires (black) and soldered then to a ring terminal. I took all the yellow wires (+12 volts) and soldered them together on another ring terminal. I took the led I had and soldered one lead to a common(black wire) and another to a red wire(+5 volts). Then I installed them on the bolts I mentioned earlier. Expect the led I just put in in a hole i drilled just large enough for it to stick thru.

Like I said refer to the website I linked to and it can guide you thru...just use good judgement and common since :worship:
Image

Image

Image

(edit) I am going to put some rubber feet under the case toa allow air flow and some vibration dampening.
User avatar
jamesm
Teardrop Master
 
Posts: 117
Images: 73
Joined: Fri Apr 06, 2007 7:17 pm
Location: Santa Maria, California

Postby Wimperdink » Sat Mar 29, 2008 1:21 pm

Hey thanks jamesm, That'll give me something to do for awhile. I was a 12 volt installer by trade not so very long ago. I'll try not to burn anything downl. :) Here's to hoping it will provide enough amperage to operate everything I need it to.
Image You know a man is on the level if his bubble is in the middle.
User avatar
Wimperdink
1000 Club
1000 Club
 
Posts: 1058
Images: 33
Joined: Mon Sep 17, 2007 8:29 pm
Location: East TN

Postby jamesm » Sat Mar 29, 2008 1:58 pm

As far as the amps...my little 350 watt power supply puts out 19 amps ..which is way more than I'll need. Good luck and let me know how it goes.
User avatar
jamesm
Teardrop Master
 
Posts: 117
Images: 73
Joined: Fri Apr 06, 2007 7:17 pm
Location: Santa Maria, California
Top

Postby Wimperdink » Sat Mar 29, 2008 3:35 pm

That should be more than enough... 12 volt accessories are a dime a dozen, and not having to rely on battery power when 110 is available is priceless. Save the battery life for when its really needed. Thanks for the linky and idea. There are a lot of work bench projects that this will work nicely for as well.

When I lived in MO, I set a car alarm up in a buddies garage so that the alarm would go off if any of the doors were opened. The buttons on the keyfob opened his 2 garage doors individually. It worked out good because things like lawn mowers and dune buggies didnt have a good place for a garage door opener so hanging the alarm remote from his key chain worked great. We powered it off of a small 12 volt transformer.
Image You know a man is on the level if his bubble is in the middle.
User avatar
Wimperdink
1000 Club
1000 Club
 
Posts: 1058
Images: 33
Joined: Mon Sep 17, 2007 8:29 pm
Location: East TN
Top

Postby justme256 » Sat Mar 29, 2008 5:30 pm

Jamesm,

One thing you might want to consider is soldering a resistor in one of the LED leads or you might find your LED failing very quickly. 5 volts is to much voltage for an LED. A typical LED has a forward voltage drop of about 2V with about 10 to 20 ma of current. There would be 2 volts dropped by the LED plus the other 3 volts dropped across the resistor.

Resistor(ohms) = Volts/Current 3V/.02 amps=150ohms

This protects the LED from an over voltage condition.

The LED you used was probably plugged into a circuit board? The resistor would have been on the board.

Larry
Last edited by justme256 on Sat Mar 29, 2008 7:42 pm, edited 1 time in total.
Bev and Larry
User avatar
justme256
Teardrop Inspector
 
Posts: 22
Images: 31
Joined: Fri Dec 28, 2007 12:30 pm
Location: Germantown, WI
Top

Postby jamesm » Sat Mar 29, 2008 7:40 pm

justme256 wrote:Jamesm,

One thing you might want to consider is soldering a resistor in one of the LED leads or you might find your LED failing very quickly. 5 volts is to much voltage for an LED. A typical LED has a forward voltage drop of about 2V with about 10 to 20 ma of current. There would be 2 volts dropped by the LED plus the other 3 volts dropped across the resistor.

Resistor(ohms) = Volts/Current 3V/.02 amps=150ohms

This protects the LED from an over voltage condition.

The resistor you used was probably plugged into a circuit board? The resistor would have been on the board.

Larry


:applause: oh good catch! I'll put one in. Thanks!
User avatar
jamesm
Teardrop Master
 
Posts: 117
Images: 73
Joined: Fri Apr 06, 2007 7:17 pm
Location: Santa Maria, California
Top

Postby jmullan99 » Fri Jun 06, 2008 9:01 am

I would suggest this is quite a good (and relatively cheap) 12V supply. However, it is not compatible with batteries. 12V is too low to maintain a charge. 13.5V would be more like it.

John
User avatar
jmullan99
Teardrop Builder
 
Posts: 45
Images: 29
Joined: Sun Jul 29, 2007 8:33 pm
Location: Niagara Falls, Ontario
Top

Postby Dee Bee » Fri Jun 06, 2008 6:27 pm

Grace happens...
User avatar
Dee Bee
500 Club
 
Posts: 696
Images: 55
Joined: Fri Jun 04, 2004 9:17 pm
Location: York, PA
Top

Postby jmullan99 » Fri Jun 06, 2008 6:57 pm

A very nice job. I like it. Your "load" works out to be 5 ohms on the 5V circuit. That is drain one amp ( 5 watts ). I know that still leaves 195W. But that puppy must put out some decent heat.


Dee Bee wrote:Here is what I built

http://www.nfdc.net/home/cbdb/Teardrop%2012%20V%20Power%20Supply.htm

Image

Dee Bee
User avatar
jmullan99
Teardrop Builder
 
Posts: 45
Images: 29
Joined: Sun Jul 29, 2007 8:33 pm
Location: Niagara Falls, Ontario
Top

Postby Alphacarina » Sat Jun 07, 2008 6:21 am

jmullan99 wrote:I would suggest this is quite a good (and relatively cheap) 12V supply. However, it is not compatible with batteries. 12V is too low to maintain a charge. 13.5V would be more like it

I agree

It's an excellent replacement for a battery, if you don't intend to have a battery in your tear at all

But if you do use a battery, couple it with a 5 or 10 amp regulated battery charger and your battery will thank you for it

It makes no sense to hook a home made 'charger' to a $100 or $150 battery and then have to replace the battery frequently because your 'charger' can't properly care for the battery

Don
User avatar
Alphacarina
500 Club
 
Posts: 826
Images: 4
Joined: Tue Jun 19, 2007 3:26 pm
Location: Ocean Springs MS
Top

Postby Dee Bee » Wed Jun 18, 2008 6:48 pm

jmullan99 wrote:A very nice job. I like it. Your "load" works out to be 5 ohms on the 5V circuit. That is drain one amp ( 5 watts ). I know that still leaves 195W. But that puppy must put out some decent heat.




I have never noticed to be any hotter than a normal computer p[ower supply and have been using one for over two years...

Dee Bee
Grace happens...
User avatar
Dee Bee
500 Club
 
Posts: 696
Images: 55
Joined: Fri Jun 04, 2004 9:17 pm
Location: York, PA
Top

Re: Computer power supply for TT 12 volt

Postby Wimperdink » Thu Jun 19, 2008 2:45 pm

A correction that I noted on other websites and from your pictures is that the green wire (power on) is actually connected to a ground wire to make this work in case others read this.

I've done this as well and I thank you for the idea Jamesm. It works wonderfully.

jamesm wrote:
I soldered the green wire (power on) to a red wire (+5 volts). I then soldered the gray wire to another +5 volt wire. I think this is the power good wire. I then took four common wires (black) and soldered then to a ring terminal. I took all the yellow wires (+12 volts) and soldered them together on another ring terminal.
Image

Image You know a man is on the level if his bubble is in the middle.
User avatar
Wimperdink
1000 Club
1000 Club
 
Posts: 1058
Images: 33
Joined: Mon Sep 17, 2007 8:29 pm
Location: East TN
Top

Postby rlphoto » Tue Oct 07, 2008 4:03 pm

Hello, I have a power supply that does not have a green wire.

I have,

Yellow
Red
Black
Purple

White
Orange
Brown
Blue
Grey

What do I do so I don't burn it up? Also, This is supposed to be a 400 watt power supply which converts to 33 amps. This is probably hype. The on the label on the PS is says 15 amps at 12v. Which is right?
User avatar
rlphoto
Teardrop Master
 
Posts: 178
Images: 12
Joined: Fri Jun 10, 2005 10:37 am
Location: near Pittsburgh Pa
Top

Postby justme256 » Tue Oct 07, 2008 4:38 pm

You need to note that computer power supplies output several different voltages. These are typically +5V +12V -12V -5V +3.3V. The voltage having the highest power output will always be +5V.

One example I found on the web is:
+5V at 30A, +12V at 6A, -12V at 0.5A, -5V at 0.5A and +3.3V at 15A

This calculates out to a 280W supply at a continuous load. The peak load spec will be even greater. You cannot look at the total power spec and apply it to the +12V output.

So the label of 15A at 12V seems reasonable for a supply with a total wattage of 400.
Bev and Larry
User avatar
justme256
Teardrop Inspector
 
Posts: 22
Images: 31
Joined: Fri Dec 28, 2007 12:30 pm
Location: Germantown, WI
Top

Postby Wimperdink » Tue Oct 07, 2008 10:42 pm

rlphoto wrote:Hello, I have a power supply that does not have a green wire.

What do I do so I don't burn it up? Also, This is supposed to be a 400 watt power supply which converts to 33 amps. This is probably hype. The on the label on the PS is says 15 amps at 12v. Which is right?


The green wire is a power on sensing wire. It must be grounded to force the power supply to power up. Does yours power up when its not connected to anything? You may find a wire label under the cover.

Here are a couple of links that should give you the info you need to make it happen.

http://web2.murraystate.edu/andy.batts/ ... supply.htm
http://web2.murraystate.edu/andy.batts/ps/POWER_OK.HTM
Image You know a man is on the level if his bubble is in the middle.
User avatar
Wimperdink
1000 Club
1000 Club
 
Posts: 1058
Images: 33
Joined: Mon Sep 17, 2007 8:29 pm
Location: East TN
Top

Next

Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: No registered users and 3 guests