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Old 11-23-2005, 11:45 AM
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Default understanding solenoids

i been lookin at em and found these

Series L04 Solenoid, 24VAC with actuator, new, never used,

Liberty Controls# H9309A with 14" leads

am i right in thinking that because they are AC then they won't reverse and are useless in a dc system, or could i use two - one in each direction of travel
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Old 11-23-2005, 12:02 PM
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AC (Alternating Current) operated solenoids will overheat if operated on DC (Direct Current). AC solenoids rely on the "Cycling" (on/off/on/off/on) to create their high impedance during operation.

The "cycling" is not present when operated from DC, so they must have their high impedance achieved through extra windings.

If you look at the coil resistance, you will find that an AC coil (solenoid) normally has a much lower resistance than its DC counterpart.

On the other hand, you can usually get by operating an DC solenoid on AC, but it may humm, Depending how desperatte you are, you can usually Rectify the AC voltage with a diode, then filter it with a capacitor to create DC from AC.

Problem is, this simple solution doesn't work the other way around!

(Took me ten years to learn what I just explained in four sentences)

Waiter
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Old 11-23-2005, 03:57 PM
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Yeah, what Waiter said. Another thing though, is that a solenoid only operates one way, regardless of the polarity of current. Double-acting solenoids are actually two solenoids that act when the coils are energized separately. Each coil pulls a piston (core) into itself when energized.

You could make a reversible solenoid with a really strong permanent magnet in the core, but it would be expensive and impractical to manufacture, and most likely very heavy with asymmetric thrust.

-- Len
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