Power source

Discussion in 'The Projects Forum' started by Bruce53, May 27, 2009.

  1. Bruce53

    Thread Starter Member

    May 14, 2009
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    I thought I posted this identical post earlier but I am unable to find it. Hope it is not a repeat. This is more electrical than electronic but here goes. I am using a '83 Chevy Blazer alternator powered by a motor on 120 Volt house current for a 12 Volt DC power source. Can someone describe or point me to a simple diagram for the wiring of this rig: alternator, battery and load. I am told the alternator has an internal regulator although I am not familiar with the internal wiring. There are three terminals on the alternator: a heavy "Bat" (obvious) and a smaller double-male plug-in labeled "1" and "2". There is no ground terminal so I assume it is frame-grounded; the plug-in terminals are too small for a ground. Delco Remy has been no help on this problem at all. Many thanks....
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, the frame of the alternator is ground. Connect the alternator frame to the battery negative terminal, and the "BAT" terminal to the battery positive terminal.

    You'll need to use a switch for the field, or you'll drain the battery when the alternator isn't running.

    See this page: http://www.hartin.com/alt.htm

    DON'T run the alternator without the battery connected.
    DON'T stick anything into the regulator bypass hole.
    DON'T use this supply indoors; the battery will emit hydrogen and oxygen gas; a highly explosive mixture. Use only in a very well-ventilated area.

    Be careful to use fuse(s) between the battery and your project. Batteries can output hundreds of Amperes for short periods of time, but if you create a dead short across the battery it can explode, spraying acid and shrapnel for quite a radius.
     
  3. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    I've got a Chevy manual for my 74 pickup that shows the need for terminal 2 to be connected to 12 volts and terminal 1 is also connected to 12 volts, but through a resistor. The value of this resistor is not given in my manual. Terminal 1 and terminal 2 are the double connectors on top. They activate the regulator transistors. It won't work without them! The manual also says there is no need for a relay (the switch SgtWookie suggested) because of the polarity of the diode, D3, supplying the field. But check this with an ammeter just to be sure I'm interpeting the information right. Other than that, I agree with Sgt Wookie's Don't list and his advocating the use of a fuse.
     
  4. Bruce53

    Thread Starter Member

    May 14, 2009
    16
    0
    Many thanks fellows, I am getting the picture. I suspect the "1" terminal is battery volts to the field; the "2" comes out of the other end of the field coil and goes to ground via a resister to control voltage. There is a "Neg" stamped on the data plate -- not sure what that means. Also a 78A meaning 78 Amps? -- I hope -- it came off of a Chevy Blazer V8 4x4. Also a "Y" meaning three phase. And three other numbers: 1105 245 and 5084, probably part numbers, model numbers or whatever. Does any of this make sense.....
     
  5. Bruce53

    Thread Starter Member

    May 14, 2009
    16
    0
    Sarge... I went to the Hartin.com site and it was a big help. Might have started there in the first place... Thanks.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Terminal 2 is connected via 12v via the ACCY contacts in the ignition switch.

    I think the resistor is the "ALT" idiot light in the dash.
    Once the alternator is generating current, it's pretty much self-sustaining, but need the battery as a load. However, it also needs to have an initial supply of current to 'get the ball rolling', so to speak.

    If terminal 1 is left connected to the battery when the alternator isn't turning, the regulator will apply maximum current to the field in an attempt to get the output up to 13.8v-14.2v. Without the alternator spinning, you'll wind up with a dead battery.
     
  7. Bruce53

    Thread Starter Member

    May 14, 2009
    16
    0
    Ok.... Thanks. I will let you guys know the outcome whatever it is.....
     
  8. Bruce53

    Thread Starter Member

    May 14, 2009
    16
    0
    Last question: I am assuming that the Delco alternator in the '83 Blazer turns clockwise as viewed from the sheave end, pulling the hot air out of the wiring?? Counter-clockwise would pull the air in, forcing it through the wiring and out the other end. Never was clear to me which it was. Thanks guys.....
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Rotate it in the direction that the alternator's fan blades are "leaning".

    The air gets pulled in through the rear to cool the bridge rectifier, and exhausted by the fan. If you turn it the wrong way, the fan will be inefficient and the bridge rectifier will overheat.

    If you have doubts, just look at an alternator in a vehicle while it's running.
     
  10. Bruce53

    Thread Starter Member

    May 14, 2009
    16
    0
    Thanks Sarge.. that's what I figured.....
     
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