Relays for water pumps

Lonemagi · Apr 22, 2003

Looking for a decent relay setup for my waterpump. I have seen solidstate and mechanical relay setups, and dont know the differance. I want something that will turn my pump on reliably when I start my pc. I could also make it myself, but really ont fel like going through the hassle if there is a good solution I could purchase.

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 22, 2003

Relays are a good way to handle pumps...

All you need is a relay with a 12vdc coil and at least single pole contacts. Connect the coil to a drive connector (yellow + and Black -) and use the points to interrupt the AC to the pump. Connect one side of the AC to common and normally open contacts so that when the computer is turned on the 12v powers the coil, the contacts pull in, switching on the pump. Mechanical or solid state relays will work equaly well but the mechanicals are a lot cheaper.

Well, if you're up to a little soldering... you can use this:
<A HREF="http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_010_008_005_000&product_id=275-206" target="_new">http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_010_008_005_000&product_id=275-206</A>

<pre>Hook it up like this...

-----------------------------------------------------
AC _______ N.O. contact To Pump
--------------------: | :--------------------------
|
____________________ __|__
12vdc + | |
____________________ | | Coil
- -----

(Curse these lousy graphics!)

</pre>.

Or if you'd rather go prefab:
<A HREF="http://www.sidewindercomputers.com/pumrelswitki.html" target="_new">http://www.sidewindercomputers.com/pumrelswitki.html</A>

(BTW... you can use a similar setup with a heavier relay and a powerbar to turn on your speakers, printer, modem etc with the computer's power button)

--->It ain't better if it don't work<---

Grub · Apr 22, 2003

Solid state relays use internal circuitry to make their connection, wheras mechanical relays use a magnetic coil to "pull" a copper bar against spring pressure to make the connection. They both will work fine for your application. Solid state relay are quieter and more reliable, but they can get warm if they are carrying a lot of current. The nice thing about solid state relays also know as SSR's is that they mostly use 5VDC as their actuation signal. 5VDC, as you know is readily supplied by your ATX P/S. You can buy lower volt DC mechanical relays, but they might be more expensive. Some jargon you might see is "SPST" or "DPST" These stand for Single pole single throw or Double pole Single throw. The "throw" is how many positions the switch in the relay has. If you have any specific questions feel free to ask. BTW you should pay more than $12.00 for a relay. You could probably cannabilize one from some electronic device as well.

Any man can withstand adversity...The true test of character is to give a man power Abraham Lincoln

Grub · Apr 22, 2003

<A HREF="http://electronics.howstuffworks.com/relay1.htm" target="_new">http://electronics.howstuffworks.com/relay1.htm</A>

Any man can withstand adversity...The true test of character is to give a man power Abraham Lincoln

Grub · Apr 23, 2003

oops...I meant "You should probably NOT pay more than 12.00 for your relay."

Any man can withstand adversity...The true test of character is to give a man power Abraham Lincoln

tombance · Apr 25, 2003

Isnt a Solid State Relau basically the same as a high current transistor with a high base voltage?

<A HREF="http://service.futuremark.com/compare?2k1=5467618 " target="_new">Almost Breaking 12k!!</A>

Teq · Apr 25, 2003

Actually a solid state relay is a device called a "Triac"... with a bit of extra circuity to switch it on and off.

A transistor won't work on alternating current.

--->It ain't better if it don't work<---

Lonemagi · Apr 25, 2003

Thanks for the info, Thinking Im just goin down to radshak and picking one up. Figure, if I want a custom rig, should make it myself (plus that fits into my plans better).

Thanks for the info, think I might read up on those solid state ones a bit more, the idea interests me.

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 25, 2003

No problem...

One afterthought... Each switch in a relay has a normally open, a normally closed and a common contact. When the relay pulls in the common contact is pulled from the normally closed to the normally open conact. When you are hooking things up, put the hot side of the AC (the plug side) on the normally open contact and then put the pump side on the common pin. The reason for this is that if you do it the other way round, you will have 110vac exposed on the normally closed contact when the pump is off, which might short to something...

Also, since you are re-wiring... why not get rid of the pump's power cord altogether and get your AC off the back of the cord connector in your power supply... usually there's accessible solder points and you can simply add your own wires to them.

--->It ain't better if it don't work<---

Lonemagi · Apr 25, 2003

Good point, Ill keep that in mind. As for the power supply, its new and under warrantee, so Im not opening it for a long time. Im pulling apart an old ps and takign the plug off of it, so it just will take a pc power cord.

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 25, 2003

That'll work too!

If you're going to do it that way, you probably should house the relay in a plastic case of some kind to prevent shorts to the case.

The last time I did this I put the relay in the PSU itself and just brought a bit of lamp cord down to the pump.

--->It ain't better if it don't work<---

Lonemagi · Apr 25, 2003

An enclosure for all the cooling electronics is going into the watercooling enclosure I have planned. Im just waiting on finding a place that can cut and drill aluminum diamond-plate for me. Once I have that, I can work on the rest.

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 25, 2003

Hey, we're talking 110VAC here... I'd still pick up a plastic project box to keep the electrics insulated no matter what it's ultimately mounted in.

One of these should work just fine:

<A HREF="http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_005_009_000_000&product_id=270-1806" target="_new">http://www.radioshack.com/product.asp?catalog_name=CTLG&category_name=CTLG_005_009_000_000&product_id=270-1806</A>

--->It ain't better if it don't work<---

Lonemagi · Apr 25, 2003

It will be a plastic enclosure, inside of the aluminum cooling enclosure. I got a ton of clear acrylic here, if Im gonna make a custom resivoir, its not gonna take too long to make the project box. I just think we had a misunderstanding here

As for radio shack, I never look at a catalog and expect the local store to have it. Ill find something there that will work at the rated amount, if not, Ill hit the harware stores.

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 25, 2003

Well... as always I prefer to err on the side of safety.
I wouldn't want to see you electrocute yourself or your computer...

--->It ain't better if it don't work<---

Lonemagi · Apr 25, 2003

Been there, done both... still here!

***
... And I'm proud to be an American, where at least I know I'm free, and I won't forget the men who died, who gave that right to me.

Teq · Apr 25, 2003

Lucky you!

As far as I can tell... 110vac hurts more than the big red wire in a monitor!

(and I be you can guess how I know...

)

The one that gets me all careful is the primary of a PSU... there's 160vdc in there! OUCH!

--->It ain't better if it don't work<---

Guest · Apr 25, 2003

The only thing I might add to what every one else has already said is: with mechanical relays there is a specification for rated contact current for each relay. You need to figure out how much current your pump will be drawing and size the relay accordingly.

Undersizing relays is bad as it will affect performance and lifespan (you don't need something more affecting lifespan of mechanical relays, the lifespan is already short).

Teq · Apr 25, 2003

Good advice... Thanks for bringing it up.

Most of the WC pumps draw about 15watts... or about 1/10th of an amp. If current handling is a concern just parallell up the switch contacts.

Also, most mechanical relays are good for about half a million cycles. Based on a twice a day on/off cycle... that's about 342 years.

--->It ain't better if it don't work<---

Guest · Apr 25, 2003

342years hah hah, my PC was obsolete 342 minutes after i bought it. I tend to look down my nose at mechanical relays after the number of times i've had to crawl up inside my autos dash to replace one.

Grub · Apr 25, 2003

Speaking of automotive relays....that is probably the best way for you to go...They are 12vDC coil, hermetically sealed, and easy to buy from the auto parts store.

Any man can withstand adversity...The true test of character is to give a man power Abraham Lincoln

Teq · Apr 25, 2003

Nope... Car relays are a bad idea... they only have 12vdc contact ratings... not a good idea on a 120vac waterpump. AC arcs more than DC and especially at 10 times the voltage. An automotive relay would probably fail in very short order.

And... if you have a 12volt pump (and they do make them: <A HREF="http://coolingflow.com/guidewck.htm" target="_new">http://coolingflow.com/guidewck.htm</A>) you wouldn't need a relay in the first place.

--->It ain't better if it don't work<---

Grub · Apr 28, 2003

*slaps own forhead*
Doh!!! I thought that the coil was rated for 12VDC, but the contacts were rated higher...thanks for the info...

Any man can withstand adversity...The true test of character is to give a man power Abraham Lincoln

Relays for water pumps

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