View Full Version : Using A Relay With Different Voltages
crazy1323
05-11-2010, 07:47 AM
As I rarely leave this section of XS I decided to post this here and it pertains to my WC build.
I am using a separate power supply for my Drives (16 total), fans (22 total), Pumps (3 D5's) and lights.
I am going to use a switch mounted on the front of the case to turn on the second power supply. The switch has a 12V LED in it while the leads to start the PSU are only .3V (checked with a multi-meter).
Can I use a simply relay so that the switch has 12V running through it so the LED works and then the relay will complete the circuit and start the PSU.
Conumdrum
05-11-2010, 08:03 AM
Sure, you can buy a 12vdc coil relay with contacts rated for such small voltages. No problem
Newark or Umm Mouser is a good place to start.
Don't quite follow your description there. You're saying the auxiliary PSU needs 0.3V to start? That sounds strangely low.
Vinas
05-11-2010, 01:37 PM
just use a spst relay to make the contact of the second PSU...
tw33ter
05-11-2010, 04:36 PM
you need a relay with a 12v dc coil (as already been said). However, the contacts on the relay are rated by AMPS, not voltage. The lower the voltage, the more amps you need for a given amount of watts.
watts = volts x amps
pooal
05-12-2010, 05:03 AM
As I rarely leave this section of XS I decided to post this here and it pertains to my WC build.
I am using a separate power supply for my Drives (16 total), fans (22 total), Pumps (3 D5's) and lights.
I am going to use a switch mounted on the front of the case to turn on the second power supply. The switch has a 12V LED in it while the leads to start the PSU are only .3V (checked with a multi-meter).
Can I use a simply relay so that the switch has 12V running through it so the LED works and then the relay will complete the circuit and start the PSU.
pc psu's have a 3v relay not 0.3v, check the green wire again when psu is in standby it's 3v. the green wire from 2nd psu can be just connected with the green wire on the 1st psu, and will then switch on and off with your 1st psu and just use switch on green wire going to 2nd psu to manually turn off if not needed. some switches have seperate poles for the internal led, what switch are you using??
pooal
05-12-2010, 05:14 AM
or you could use a 12v wire from 1st psu and then after the led light switch use a led light dimmer switch for $8 from ebay to turn voltage down to 3v to start 2nd psu? thats what i'd do!! saves searching through relay specs to get the right one :up:
Waterlogged
05-12-2010, 12:43 PM
Why not just use something like this?
http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=34_186&products_id=21193
crazy1323
05-12-2010, 05:29 PM
Because I like having a switch on the front to turn on only the 2nd PSU so I can do things like leak testing.
Waterlogged
05-12-2010, 05:32 PM
Then I'd think all you'd need is something simple like this.
http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=34_186&products_id=3163
meanmoe
05-12-2010, 05:43 PM
Or buy something like this:
http://jab-tech.com/24pin-power-supply-starter-with-jump-wire-pr-3597.html
use the green and black wires, splice it yourself. Get a little 3 position switch or a 2 position and a diode and you're good to go... I thinik... would he need a current limiter? (I'm no EE)
Then I'd think all you'd need is something simple like this.
http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=34_186&products_id=3163
With this though he's not guaranteed to have them both on at the same time... i.e. power to the motherboard but none to the pump...
Edit: is it ok to directly connect one psu to the other?
Vinas
05-13-2010, 06:09 AM
You guys may have beat me to it, but I was browsing some parts and came across a solution to the OP's problem... The Lian Li Dual Power Supply Adapter Cable (http://www.frozencpu.com/products/5637/cpa-167/Lian_Li_Dual_Power_Supply_Adapter_Cable.html). Hope this helps!
neonblingbling
05-13-2010, 07:18 AM
Cant you just wire the LED to a molex on the secondary PSU, and have a separate switch to turn the (secondary) PSU on or off? Sure it's another pair of wires, but it seems simpler...
pooal
05-13-2010, 06:50 PM
Because I like having a switch on the front to turn on only the 2nd PSU so I can do things like leak testing.
so what your saying is you want the 2nd psu to turn on with the 1st psu(main) but also be able to run the 2nd independantly(without the 1st psu) for this you will have to link the relay wires(green wire on the 24pin plug) best use the lian dual psu connector os similar for that, than use a 3 way/position switch on the green wire going to the 2nd psu, the 3 way/position switch would disconnect the green from the 1st psu(so it dont turn on when your just running the 2nd by itself)and reconnect it to a ground to complete the relays circuit, the 12v led is a major burden bro, i would leave it out of this wiring and just light the little sucker yourself from one of the many 12v wires, just use heatshrink or sleeve to tidy up!! if you need a 3 way/position switch i can def help there, i can get one from dicksmiths or jaycar down the road for ya, just send me a pm :up: