Question Old PSU Power Rail Wire Question (12v 17a) ?

[aveatquevale]

OK, according to the sticker on the PSU, it has an output rail for 12v 17a, which I need to power an automobile seat.

edit: The seat is for a SimRig I'm building at home. Sorry for the confusion.

First things first, can it be done ? I have received intel that it is sufficient to use the 2 electrical contacts on the seat for power for my seat to work. Can I use this PSU for this purpose ? Will flipping on the power on off switch behind it be enough to power the seat ? The seat works with 12v and anywhere from 5A and up. The seat has motors for height and backrest incline to be precise, it's not for heating or anything like that. It also has intact airbags in it tho.
If it indeed can be done, which of the pictured wires are for the 12v 17a rail ? Also, the psu won't be powering anything else at the same time.

https://imgur.com/T09pxce

View: https://i.imgur.com/T09pxce.jpeg

https://imgur.com/YKezi0r

View: https://i.imgur.com/YKezi0r.jpeg


Many thanks in advance to anyone who looks or posts a reply.

 

[Aeacus]

which of the pictured wires are for the 12v 17a rail ?

Every 12V wire is on the 12V rail since it's single rail PSU.

Easiest connector would be EPS12V 4-pin, since it carries two 12V wires. But MOLEX also has 12V wire on it. The yellow ones. Red one is 5V and black is ground.

which I need to power an automobile seat.

Why you can't use the car's own electrical system for that? Also, from where you plan to get the AC to power the PC ATX PSU? Car engine (alternator, battery) only output DC.

Personally, i wouldn't use that PSU for anything. It is not 400W unit, but instead 200W one. Can go "boom" at any given moment.
And how do you plan to turn the PSU on and off on command?

 

[USAFRet]

which I need to power an automobile seat

What happened to the original power situation in the car?

A computer PSU is not suitable for this.
Where would it get the expected incoming wall power?
And that "Everest"....that is too janky to use in Anything, not even a boat anchor.

 

[Ralston18]

No. Do not use the PSU.

As above (per @Aeacus ) there are multiple issues with what is being considered.

The PSU is intended to support computers not a car seat. Even though the PSU may appear to be workable on paper longer term use at max voltage and amperage is not going to end well.

Fix the car seat properly with a power source matched to the car's electrical system and motors.

 

[Ralston18]

And will also second @USAFRet .

 

[aveatquevale]

@Aeacus​

@USAFRet​

@Ralston18​

​

First and foremost, my heartfelt thanks for dropping in and sparing your time to answer.


Secondly, apologies since I should've clarified at the beginning. The seat is for a SimRig I'm building at home, and the electrical power is only needed when I need to adjust the seat up and down and the backrest incline front to back. Otherwise, the power will be turned off via the button on the psu. As expected with a psu, it will be plugged to a wall outlet thru a regular psu power cable.

Typically, people who work on these kinds of 'projects' use external power supplies (such as the one seen below), a laptop power adapter if the amps are adequate, or a power supply unit which I think is perfectly capable of delivering the required volts and amps.

https://imgur.com/2CqHrkK

View: https://i.imgur.com/2CqHrkK.jpeg


BTW this is the kind of connector on the seat side - the wide and flat double connector seen in the middle of the yellow box:

https://imgur.com/OxAgNZc

I've been told a FIS or FS connector attached to these will do the trick, however I think I need to peel the cables on the PSU, and solder them to the FS connector, is that right ?
View: https://i.imgur.com/OxAgNZc.jpeg


I've been told just connecting the power will do the trick, since this is a pretty basic seat with no complicated electronic stuff such as an ecu, or the like. I guess I need to know which color wires go one way, and which colors the other.

 

[USAFRet]

I've been told just connecting the power will do the trick, since this is a pretty basic seat with no complicated electronic stuff such as an ecu, or the like.

And still, "computer power supplies" don't work like that.
Just flipping the switch on the back does not 'turn it on'.

 

[aveatquevale]

@USAFRet

Tempting fate right now

https://imgur.com/B6nFkyj

View: https://i.imgur.com/B6nFkyj.jpeg




Joke. Good thing the seat's at the office, and not at home with me at this time. The 'experimentation' will have to happen sooner or later tho. Feeling like a nuclear physicist before the first atomic test lol

 

[aveatquevale]

@USAFRet​

Thoughts on this ?

View: https://www.youtube.com/watch?v=SVcXzhLINQU

 

[aveatquevale]

@Aeacus ,

Since there are two power contacts on the seat, one yellow from the molex goes to one contact, and one black from the molex, goes to the other contact, would that be correct ?


Another question: It sez 17 amps at 12 volts. Since 12 v is the yellow wire and there are 5 of em coming out of the psu, does that mean each yellow wire carries 17/5 = 3.4 amps roughly ? I've heard these seat motors will turn the screws with as low as 5 amps depending on the seat model, so worth a try with connecting 2 yellows to one side of the seat contact, and two blacks to the other ?

 

[DSzymborski]

I gotta agree with the others; this PSU is so old and low quality that I wouldn't even trust it to power a grilled cheese sandwich. Giving advice about using this is hard to do ethically given the risk.

 

[Aeacus]

Thoughts on this ?

This is the ONLY way to turn on the PSU without MoBo.

does that mean each yellow wire carries 17/5 = 3.4 amps roughly ?

No.

Single-rail PSU is able do deliver all it's Amperage on single wire. However, there are limitations of what wires, themselves are capable of. And to play it safe:
MOLEX +12V wire is rated for up to 5A (60W)
ATX 20-pin +12V wire is rated for up to 6A (72W)
EPS12V 4-pin +12V wires (both combined) are rated for up to 16A (192W)

So, 12V cables, with 2x in MOLEX (5A), 1x in ATX 20-pin (6A) and 2x in EPS12V (16A) = 32A what wires, themselves, would be able to sustain. Of course, PSU itself isn't capable of delivering 32A on 12V rail, but instead only 17A.

However, for more accurate Amperage, it isn't that easy.

The maximum current that can be carried is a function of the maximum temperature of the housing (105°C) and the maximum temperature of individual connection (30°C) (and maximum temperature of wire insulation) (and length of wire) (and ambient temperature). More wires, the less total current.

From Tyco data sheet for Amp connectors.



Table shows number of circuits vs size of wire. Larger wire = more current. Less wires = more current. Derating connector due to adjacent conductors.

Source: https://superuser.com/a/1654588

MOLEX connector wires are usually 18 gauge wires. Based on the image you linked, it looks like every wire from PSU is 18 gauge.

Also, PSU won't output it's full rated Amperage as soon as you power it on. Instead, it's the component on the other end that draws as much Amperage it needs, essentially telling to PSU how much to deliver. If PSU can deliver what is asked of it, then good. If not, "boom" + magic smoke. (Higher-end PSUs would shut themselves just off, without blowing up.)

so worth a try with connecting 2 yellows to one side of the seat contact, and two blacks to the other ?

In theory yes. However, i'm not sure in the reliability of your PSU and advise against using it in this way.

Much safer would be contacting seat manufacturer and asking them what kind of PSU is intended to use with their seat. Better to get appropriate unit to power the seat, rather than jerry-rigging something to it.

 

[aveatquevale]

@Aeacus ,


Thanks a lot, you guys have been really helpful. I'm not really hopeful about finding the intended plug for the seat contacts especially where I live, even less so one with the other end that can be connected to an appropriate power supply, a laptop brick or the like that is intended to be plugged into a wall outlet. I'll have to wing it one way or another, and as long as I don't start a fire, hurt someone, or damage things on the seat side, I'm fine. The old psu going kaput won't vex sleep.


One last question: As a rook, I've heard which contacts don't matter, as long as I put the yellows on one side, and the blacks on the other, is that right ? I mean none of the 2 contacts are really intended to be used with only +, or only -. Just the polarity will be reversed, am I right ?

 

[Zerk2012]

You can just buy a convertor for about 50 bucks.

 

[Aeacus]

One last question: As a rook, I've heard which contacts don't matter, as long as I put the yellows on one side, and the blacks on the other, is that right ? I mean none of the 2 contacts are really intended to be used with only +, or only -. Just the polarity will be reversed, am I right ?

If you go through this, then i'd use the EPS12V 4-pin +12V and ground wires since inside the PSU, this connector is designed to handle higher W and A than MOLEX is. And it can be different circuitry inside the PSU as well, better sustaining higher load.

Now, polarity is another concern, since while some motors doesn't care which contact is used as + and which as - (e.g you can freely swap them around), some motors require to have correct polarity. Using incorrect polarity can seize the motor up (essentially making it to spin in reverse, thus breaking it).

 

[DSzymborski]

As long as I don't start a fire, hurt someone, or damage things on the seat side, I'm fine.

Which is why people are encouraging you to not use this PSU.

 

[aveatquevale]

@Aeacus
Afaik the motor has two way action. Which in theory means it shouldn't really care ?

@DSzymborski​

Noted. I'll be placing a 40x40 ceramic tile under the psu to isolate it from the surroundings, in case it fails catastrophically. But I doubt it. The motors pull about 15 amps at stall, and pull about 5amps when they're on the move.

 

[Eximo]

Powering motors isn't exactly the same type of load as powering a computer. That 15A max might actually trip the PSU (if it has over current or under voltage protection) Might even have a fuse in there that will blow. Older regulated PSUs also expect some load on the 5V and 3.3 volt rails, having none may result in incorrect voltage output for 12V under a load, again potentially tripping over or under volt protections.

I think going after one of those dedicated 12V power supplies is the smarter move to make.

 

[stonecarver]

Maybe just under thinking your project but could a battery AKA like where your seat came out of a car that used a 12 v battery originally.

Like those Walmart grey curtesy shopping scooters. A battery from something like that. Get one of those self regulating battery menders AKA smart chargers and life would give power to the seat and the battery would stay healthy.

If those batteries from one of those scooters can move grandpa around Walmart or out there around town on his own scooter and he is plugging it in at home.

Just another option to send your way.

 

[aveatquevale]

@Eximo ,
@stonecarver ,


Thanks for your contributions, good to know. I think I will not rush this and look into more suitable options to power the seat. The psu may no longer serve even as a last resort.

 

[Aeacus]

Afaik the motor has two way action. Which in theory means it shouldn't really care ?

In this case, only the controls would be flipped. E.g you push Up but since motor polarity is reversed and it spins backwards, end result is Down.

 

[aveatquevale]

I'm happy to report it worked without a hitch, although I must admit I had my reservations so I spared no expense on precautions, not only a ceramic tile was used, but also bricks on 3 sides to isolate the psu as much as possible without getting in the way of the cables/wires, and a 12 kg fire extinguisher was at the ready.


And just as you said, the contacts I picked were in reverse order which meant the up function worked as down. It's 'disassembled' for further 'evaluation' down the line