Does anyone know anything about solenoids?

[rdagger]

I picked up a 3/8" 2-way solenoid valve on eBay. It appears to be 12-24V (250 PSI) so I am running it at 12V using an old computer power supply. It appears to work, but it is getting very hot. After about 5 minutes the solenoid's plastic casing heats up to around 210°F and the plastic starts to smell. It appears to be pulling about 5A at 12V and the computer power supply is pulling about 90 watts at 110V. Is this normal or am I doing something wrong?

[ChadTower]

Hard to say if it's normal without knowing the exact specs.  They vary so much.  Doesn't sound good, though.  That seems wrong to me, 5A at only 12V.  Might just be consuming too much juice for that voltage.  I'd try again with a 24V power source.

[rdagger]

Hard to say if it's normal without knowing the exact specs.  They vary so much.  Doesn't sound good, though.  That seems wrong to me, 5A at only 12V.  Might just be consuming too much juice for that voltage.  I'd try again with a 24V power source.

I tried a 24V p/s from a big old laser printer, but it instantly blew the 3.25A fuse.  I dont' have any other 24V supplies.  I thought about connecting the +12V & -12V on the computer p/s, but although the +12V is rated at 8A, the -12V is only rated at 1A.  Is it possible that the solenoid is 24V AC?

[ChadTower]

Well if it's drawing 5A of course it's going to blow a 3.25A fuse.  You need a power supply that is rated properly.

A bare solenoid by itself wouldn't work very well on AC... the polarity of an electromagnet is determined by the current flow's direction... so, an AC magnet (i.e. the solenoid) would have its poles alternating sixy times per second.  Not exactly all that useful for a solenoid.

[rdagger]

I found 24/60 written on the bottom of the solenoid.  Apparantly, there are AC solenoids.  This leads me to believe that the solenoid might be 24V AC 60Hz.  I just have to find a 24V AC p/s to confirm.  Anyone know of any good sources for 24V supplies? 

[ChadTower]

Is it enclosed in a casing or something?  If it's AC I would think it would need a voltage regulator and a bridge rectifier in there.  But if it says 24/60 then yeah it's probably AC.

[Ken Layton]

Yes, your solenoid is 24 volts AC and 60 hz.

There are also two types of solenoids: "continuous duty" and "intermittent duty". Judging by how quickly yours got hot I'd say you have an intermittent duty type. This means it is only designed to be powered on for no more than 30 seconds, then off for at least ten minutes (lest it burn up or catch fire!).

[ChadTower]

But we love the smell of burnt enamel!

[rdagger]

Yes, your solenoid is 24 volts AC and 60 hz.

The solenoid is definitely AC.  I tried a small 24V .8A AC power transformer from a dead DSL modem and it works great.  After several minutes, the temperature is only 100°F and the valve is wide open.  Although I don't know if this transformer will be powerful enough for long term usage because it is rated for 30 watts and it is currently pulling 30 watts at 110V.  Also, the transformer is running kind of hot at about 125°F.

[ChadTower]

If the transformer is maxed, it's too small.

What is this solenoid for, anyway?

[rdagger]

If the transformer is maxed, it's too small.

What is this solenoid for, anyway?

I have a fountain in my front yard.  I placed a water sensor in it and built a circuit that automatically tops off the water level.  The solenoid controls the water valve that fills the fountain.

[ChadTower]

Nice.