Starter Solenoid

Discussion in 'General Electronics Chat' started by hovik, Dec 9, 2009.

  1. hovik

    Thread Starter New Member

    Sep 21, 2009
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    I'm trying to use a starter solenoid as a relay in my circuit, but I can't really find any datasheets or diagrams for my solenoid. How high voltage/current do the starter solenoid need to be applied to the "starter trigger terminal" for it to be triggered?
     
  2. BMorse

    Senior Member

    Sep 26, 2009
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    If it is an automobile starter, 12 Volts DC.
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
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    In case you don't know, most solenoids are rated for "intermittant duty" which means they should only be energized for short periods of time.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    What Gerty said.

    Energized for very short periods of time. And the coil will probably draw a large amount of current.

    The contacts can carry several hundred Amperes of current.

    Why don't you tell us more about what you are trying to do?
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    I may be wrong but, I think he is talking about a Ford/Chrysler style solenoid. They were mounted on the inner fender and only switched the current to the starter, not engage the gear like a GM.

    [​IMG]

    Like this one. They are made for continuous duty.

    Cary

     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    Solenoids are all meant to momentarily apply power to a starter Motor (which drives the gear to start an engine...)... regardless of make and model of the automobile... If the solenoid stayed engaged, the starter motor gear would be damaged.... Continuous duty solenoids like those are also used in other high current applications in automobiles/trucks, most trucks that have a tommy lift in the back uses one or 2 of these to turn on the hydraulic pumps for the lift...


    Read this to understand how solenoids and starters work together >>> http://www.samarins.com/glossary/starter.html
     
  7. hovik

    Thread Starter New Member

    Sep 21, 2009
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    I'm actually using a starter solenoid from a Ford like the one , it was mounted on the fender on the left side of the car by the battery. I'm using two of them instead of a bi-positional switch. And there is suppose to be running current trough one of them continually. Is that a problem, or are they made for continuous duty?

    It looks like this:
    [​IMG]

    My problem is that I can't seem to find out where the neutral is.. because I measured no resistance between the start-trigger that is the middle screw and the bottom part that I thought was neutral...

    Also, does it matter which way the current runs trough the solenoid after it is turned on? If so, how do I find out which screw I am suppose to connect to the battery?
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    With only one coil terminal- the case is the second. Measure coil resistance, under about 6 ohms, probably intermittant duty, around 20 probably continuous.'Ben awhile since i measured one.
     
  9. whatsthatsmell

    Active Member

    Oct 9, 2009
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    The "ground" on that solenoid is through the base - where it attaches to the fenderwell.

    There are 12v solenoids designed specifically for continuous duty (do a google search). You can find them at marine supply and RV supply stores, and I'm sure NAPA has them too.

    They are usually more expensive - about $25 - $100.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    There IS no "neutral".

    The mounting tabs are normally connected to the body of the vehicle, which supplies a ground.

    The small terminal powers the relays' coil.

    The two large terminals are the connections from the source of current to the load. It does not matter which way the current flows through the relay.

    Those relays can carry several hundred Amperes of current. I do not know if they are rated for continuous duty.

    Normally, a starter relay would only be engaged for a maximum of 30 seconds before allowing the starter motor to cool off for several minutes. If a driver tried to keep cranking the engine for much longer than that, there is a good chance they could permanently damage the starter motor.
     
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