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Building a transistor starter interrupt. - 90 Honda

Discussion in 'Electronic Basics' started by Sam Nickaby, Feb 14, 2006.

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  1. Sam Nickaby

    Sam Nickaby Guest

    I notice that on some new automotive security systems there is a
    starter interrupt that uses a transistor instead of the usual relay to
    disable power to the starter solenoid. A small current is supplied to
    this transistor and the car can be started. It's usually located at the
    starter solenoid. Usually I use a relay to disable the solenoid but I
    noticed that even the biggest stock relay leaks current. It leaks because
    when I start the car using a relay the car won't start. But when I bypass
    the relay it starts fine. Where can I obtain these unique transistor?

    Thanks
     
  2. Keep YerSpam

    Keep YerSpam Guest

    mouser.com
     
  3. Mike Romain

    Mike Romain Guest

    You are describing dirty connections. Using electronics instead of
    electro-mechanical is still subjected to the dirty connection.

    Relays don't leak' current, dirty connections or contacts can fail to
    pass current.

    Mike
    86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
    88 Cherokee 235 BFG AT's
    Canadian Off Road Trips Photos: Non members can still view!
    Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
    (More Off Road album links at bottom of the view page)
     
  4. Steve W.

    Steve W. Guest

    I doubt you actually know much about how an interrupt works when you
    don't understand the way a vehicles alternator works.
    Reference your earlier post. Maybe you should take some classes in
    electronics first.

    "I have been thinking of a good way to prevent stranding
    myself from a dead battery. It happened twice. Once at a
    beach from leaving my lights on. The other was at a college
    campus which the stereo and the dome light ran down the
    battery. Unlike the beach, the college campus have lots of
    helpful students with beat up cars that have jumper cables.
    Now, I have a new idea. Once my battery runs dry, I
    remove my alternator belt and wrap a rope around the
    alternator pulley. I then pull the rope so it'll turn 10
    revolutions per pull. I keep doing this for about 20 times.

    What is the possibility that this will supply enough charge
    to start the car. If not, can somebody think of a clever idea
    to start an automatic?"
     
  5. Steve

    Steve Guest

    This is complete nonsense. Relays don't "leak" current. And the biggest
    "stock relay" I can think of is <ta daa> a Ford starter relay and those
    buggers can carry 200+amps (the whole draw of the starter MOTOR, not
    just the solenoid).
    Put down the $1.50 Harbor Freight crimp tool, and step AWAY FROM THE CAR.
     
  6. Steve W.

    Steve W. Guest

    Ford relay is a baby compared to the ones we have on our fire engines.
    The relays for the booster reel drives and the primer pump look like
    Ford units on steroids. They have 3 connections. Two in from the
    batteries and one HEAVY one out to the primer or they reel. They can
    take 400 amps BUT they only handle about 1/4 of that normally.
     
  7. Sam Nickaby

    Sam Nickaby Guest

    Thanks. You guys are correct, relays don't leak current. The word
    I was looking for was resist current. Will the transistor resist more
    or less current compared to the relay? What is the name of this
    transistor if I were to find one at mouser.com?

    Thanks
     
  8. Mike Romain

    Mike Romain Guest

    I have a funny feeling you are using a relay on the main battery power
    line to the solenoid? Usually the cut off relays are on the solenoid
    trigger line and a standard 30A Bosch relay will work perfectly for
    that. The current is really low there. That type of relay will not
    pass starter current, it will arc out internally.

    I replaced my headlight switch with a stock Bosch relay and my lights
    went an amazing bright white in color. The Bosch relay has 'way' less
    resistance in it than the new GM headlight switch I have in there.

    No relay, electronic or mechanical will work well with bad connections
    to it. I prefer to use crimp connectors with solder in them and heat
    shrink on top for corrosion resistance because most of my wiring is open
    to the weather and occasional underwater use.

    I am not well versed on totally electronic relay types, sorry. That was
    someone else posting about them, I still like the simple Bosh style
    ones.

    Mike
    86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
    88 Cherokee 235 BFG AT's
    Canadian Off Road Trips Photos: Non members can still view!
    Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
    (More Off Road album links at bottom of the view page)
     
  9. Bobscar

    Bobscar Guest

    Do transistors resist more current than relays? Yes they do, however
    there has been some development on power devices such as MOSFETS,
    IGFETS, and smart power devices as yet to be in widespread general use.
    You could use a relay driven via a transistor with a reverse connected
    diode across the coil to absorb the switch off transisents.

    Bobscar
     
  10. Bobscar

    Bobscar Guest

    Do transistors resist more current than relays? Yes they do, however
    there has been some development on power devices such as MOSFETS,
    IGFETS, and smart power devices as yet to be in widespread general use.
    You could use a relay driven via a transistor with a reverse connected
    diode across the coil to absorb the switch off transisents.

    Bobscar
     
  11. « Paul »

    « Paul » Guest

    Mouser may not carry what you need.
    Put ST780C06L0 or ST780C04L0 into Google.
    One of those should handle the current.
     
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