run AC solenoid valve on DC?
tne...@yahoo.com
eliminate the loud buzz. To test, I connected a variable DC supply,
and ran the voltage up to the point where they opened reliably, about
46VDC IIRC.
On DC, The coil heated up to about the same temp as on AC (using the
finger test). Problem is, the valve will not reopen consistently at
the same DC voltage, after warm up. I tried increasing the DC voltage,
but the coil seems too hot, and still does not reopen consistently.
Cold vs hot coil ohms is the same.
Why is this happening on DC?
DC parts can be ordered to properly convert them, if necessary, but
I'd rather
DIY if possible.
Tim Perry
"tne...@yhoo.com" <tne...@yahoo.com> wrote in message
news:2c6c760a.0409...@posting.google.com...
> I thought I would run these 125VAC coil 1.25" solenoid valves on DC to
> eliminate the loud buzz. To test, I connected a variable DC supply,
> and ran the voltage up to the point where they opened reliably, about
> 46VDC IIRC.
>
> On DC, The coil heated up to about the same temp as on AC (using the
> finger test). Problem is, the valve will not reopen consistently at
> the same DC voltage, after warm up. I tried increasing the DC voltage,
> but the coil seems too hot, and still does not reopen consistently.
> Cold vs hot coil ohms is the same.
> Why is this happening on DC?
check to see if the "rod" (the part the electromagnet pulls) is becoming
magnetized. try reversing polarity and see what happens.
Andrew Gabriel
"Tim Perry" <timperry...@adelphia.net> writes:
>
> "tne...@yhoo.com" <tne...@yahoo.com> wrote in message
> news:2c6c760a.0409...@posting.google.com...
>> I thought I would run these 125VAC coil 1.25" solenoid valves on DC to
>> eliminate the loud buzz. To test, I connected a variable DC supply,
>> and ran the voltage up to the point where they opened reliably, about
>> 46VDC IIRC.
>>
>> On DC, The coil heated up to about the same temp as on AC (using the
>> finger test). Problem is, the valve will not reopen consistently at
>> the same DC voltage, after warm up. I tried increasing the DC voltage,
>> but the coil seems too hot, and still does not reopen consistently.
>> Cold vs hot coil ohms is the same.
>> Why is this happening on DC?
>
> check to see if the "rod" (the part the electromagnet pulls) is becoming
> magnetized. try reversing polarity and see what happens.
This happens with the 3-port valves commonly used in the UK on
heating systems. In one mode, the coil is energised with DC
(to lock the armature). When the voltage is removed, the valve
is supposed to return under spring tension, but normally it stays
locked in place due to residual magnetism induced. The way this
is solved is to provide a very tiny AC current through the coil;
a resistor is used to allow a milliamp or two of AC to flow in
the coil whenever it isn't energised, and this instantly clears
the residual magnetism and allows the armature to move under
spring tension.
--
Andrew Gabriel
daestrom
> eliminate the loud buzz. To test, I connected a variable DC supply,
> and ran the voltage up to the point where they opened reliably, about
> 46VDC IIRC.
>
> On DC, The coil heated up to about the same temp as on AC (using the
> finger test). Problem is, the valve will not reopen consistently at
> the same DC voltage, after warm up. I tried increasing the DC voltage,
> but the coil seems too hot, and still does not reopen consistently.
> Cold vs hot coil ohms is the same.
> Why is this happening on DC?
>
When the slug of the solenoid is out of the AC coil (the position its in
when the power is off), the AC coil has no iron core and thus has low
inductance. So when power is first applied, the only impedance is the
resistance of the coil. So, a higher than normal current flows through the
coil.
This higher current generates enough 'pull' to pull in the slug. But as
soon as that happens, the inductance goes up and the current goes down. The
lower current will generate enough 'pull' to *hold* the slug in place. And
that is the current that the windings are designed to handle for long
periods of time.
By using a lower DC voltage, you are getting the same current as the
windings are normally designed to handle to *hold* the slug in place. But
this isn't enough current to *pickup* the slug.
Some large DC contactors/relays have a resistor in series with the coil, and
a normally closed contact in parallel with the resistor. So when power is
first applied, the resistor is shorted by the contacts and a large current
flows through the coil. Once the coil 'picks-up' the armature of the relay,
the NC contact opens and inserts the resistor in series with the coil. This
reduces the current to a lower value that the winding can take.
AC coils get that same effect for 'free' by using the variation in the
inductance of the coil as the slug moves into the coil.
Bottom line, solenoids designed specifically for AC, often cannot work on
DC.
daestrom
Bill Kaszeta / Photovoltaic Resources
I have often operated ac solenoids from dc photovoltaic power systems.
My solution is to measure the ac current, then add a series resistance
in the DC circuit to reduce the current to the AC value. Then, place an
electrolytic capacitor across the resistor, usually 250 MF at the
DC voltage or higher. The capacitor produces an initial surge into
the coil until the capacitor charges up. 24-VAC solenoids work
well on 12 volts DC with a resistor about equal to the DC resistance
of the coil. My experience is with 1/4" solenoids, you may need a
larger capacitor.
Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA
bi...@kaszeta-removethis.org
daestrom
"Bill Kaszeta / Photovoltaic Resources" <kaszetaw...@mindspring.com>
wrote in message news:413e6148...@news.east.earthlink.net...
Now, why didn't I think of that!!! Of course, need to be sure the surge is
enough to pick it up, but even if it doesn't, it won't burnout because the
resistor is always in the circuit.
daestrom
No Spam
<snip>
>
> <sound of hand slapping forhead..>
>
That's called a "Blond high five!" :-)
KWS
current through which will let the solenoid activate, then as the PTC
heats up, current is reduced. If the solenoid is decativated and
activated again before PTC is cooled completely, it might not activate
however.
This is the very thing that makes the BUzzzzzzz sound when you turn on your
TV.
Ken
"~Dude17~" <dud...@sacbeemail.com> wrote in message
news:b959931f.04090...@posting.google.com...
> X-No-Archive: Yes
>
> "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote in message
news:<prr%c.15959$2s....@twister.nyroc.rr.com>...
> What about using a PTC resistor? When turned on, it allows a large
> current through which will let the solenoid activate, then as the PTC
> heats up, current is reduced. If the solenoid is decativated and
> activated again before PTC is cooled completely, it might not activate
> however.
rickyrockrat
Hello, any need for the diode in parallel with the coil for the back current
when switching off when operating with DC?
--
for full context, visit https://www.polytechforum.com/electrical/run-ac-solenoid-valve-on-dc-15932-.htm
gfre...@aol.com
<0f8503901d844703ee...@example.com> wrote:
>replying to Bill Kaszeta / Photovoltaic Resources, rickyrockrat wrote:
>Hello, any need for the diode in parallel with the coil for the back current
>when switching off when operating with DC?
nickel, why not?
You can get a pretty good idea of what voltage to use with an ohm
meter. DC is easy.