Stealthy electronic voltage regulator trick - Chevelle Tech
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post #1 of 22 (permalink) Old Aug 12th, 07, 1:30 AM Thread Starter
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Keith
 
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Stealthy electronic voltage regulator trick

Stealthy Electronic Voltage Regulator tip.

For those of you restorers out there who must have an original NOS stamped Delco external regulator for appearance and judging reasons, but hate the constant trouble with that prehistoric mechanical regulator, there's an easy and stealthy fix that won't cost you points at the show.

The trick is simple. Keep your stock NOS Delco regulator box, but open it up and install an electronic voltage regulator inside. What kind of regulator? Easy! You can easily wire an LM317 voltage regulator into the inside of your old mechanical regulator box. The LM317 is a cheap, easily available 1 amp regulator chip, and is widely used by electronic tinkerers everywhere. You can buy one at Radio Shack for about 3 bucks. There's even a schematic on the package.

The mechanical voltage regulator is a complex device doing a simple job. There is no voodoo going on in there. Back in the days of the dinosaurs, the sole purpose of the mechanical regulator was to act as a hi-lo switch to alternately load and unload the alternator with a roughly calibrated reference voltage range. This was so that your alternator could get a rough idea of system voltage and thereby (in theory) not overcharge the battery. Your alternator sees the reference voltage as a measure of battery condition and charges or idles accordingly. In contrast to your mechanical vibrator masquerading as a regulator, using the LM317 the output is held at precisely the voltage you select. Your battery is very happy, your charging system is stable, and no more "stuck regulator syndrome".

Don't let the term "chip" scare you, either. The LM 317 is a three lead package. The circuit is SIMPLE! Follow the schematic on the Radio Shack package, or look online. Physically, you can simply disconnect your mechanical regulator wiring inside the box and substitute the LM317 on the appropriate leads. It is quite small. Hide the whole circuit inside the old regulator box. You can even mount a trim pot and trim the output of the LM317 to precisely the reference voltage recommended in your GM service manual.

When you connect the regulated output of the LM317 to the factory wiring which feeds to your stock old school GM alternator it will keep your charging system at that same reference voltage at all times...just like a modern electronic regulator. Steathy, cheap, and WAY better than the old mechanical regulators!

Now you can have it both ways... original wiring, NOS regulator box, happy judges and the comfort and ease of an electronically regulated alternator.

An added benefit is that when your system is at nominal charge, the regulator won't be cycling off and on and off and on and off and on...causing your lights to get dim and bright dim and bright dim and bright... AHHHH!!!!
:-)

Cheers,
CBG
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post #2 of 22 (permalink) Old Aug 12th, 07, 4:34 AM
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Re: Stealthy electronic voltage regulator trick

Why not post a picture of your install and wiring schematic. This looks like great idea and I for one would love to see more detail.

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post #3 of 22 (permalink) Old Aug 12th, 07, 6:07 AM
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Re: Stealthy electronic voltage regulator trick

Here's the data sheet for the LM317 with some schematics at the bottom.

http://cache.national.com/ds/LM/LM117.pdf
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post #4 of 22 (permalink) Old Aug 12th, 07, 6:14 AM
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Re: Stealthy electronic voltage regulator trick

Great info but all I was asking for is how you would wire it into your existing regulator and connect which leads where???
Can you provide that and maybe a photo???

Thanks much!!!!!!

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post #5 of 22 (permalink) Old Aug 12th, 07, 9:27 AM Thread Starter
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Re: Stealthy electronic voltage regulator trick

Yes, I'll see what I can do on that. It'll take a couple days...but not too long, because I'm filing lead on a quarter panel, so I'm sure I'll need to find a reason to take a break. :-)

Cheers,

cbg
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post #6 of 22 (permalink) Old Aug 12th, 07, 11:26 AM
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Re: Stealthy electronic voltage regulator trick

Well, in theory your idea may be good. However, upon reading the info you supplied, I see that the MAX output of the 317 is only 2.4A. Not quite what the car need to see. If you were to run just an HEI unit on this current, it wouldn't take too long to smoke it. Just a heater blower on full would cook it.
Now, since I don't have an electrical degree, I may be all wet, this is just what I gather from reading the PDF. file.

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post #7 of 22 (permalink) Old Aug 12th, 07, 12:24 PM Thread Starter
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Re: Stealthy electronic voltage regulator trick

Dave,

re; 2.4 amps LM317

I understand how you could be concerned by the seemingly low current capacity of the LM317, however it is vital to understand that the Delco automotive voltage regulator (either mechanical or electronic) does NOT actually handle any of the current loads for your vehicle's various electrical systems. Those are drawn directly off the B+ bus, or in the case of the starter motor, directly from the B+ battery terminal, via the starter relay.

You are correct to state that if the operational current loads of your electrical systems were drawn through ANY voltage regulator, it would quickly be destroyed by the heavy current of things like your heater blower, your headlights, or (as you pointed out) your HEI. That is why this device is called a "voltage regulator".

If you examine a typical Chevelle schematic, such as found on 12-57, fig. 98 of the 1966 Chassis Service Manual, you'll see that the alternator OUTPUT wire 12R is connected through a common lug on the horn relay and then through the junction block and to the B+ bus of your car. This is where all the heavy lifting occurs. Note that this B+ output of the alternator is NOT where the voltage regulator connects. this B+ output is the retified output of the alternator that supplies energy to the B+ bus, and thereby charging your battery. These two points are the sources to feed the heavy current loads of the system.

If you examine the schematic further, you'll see that wire 20R to the factory regulator is only a clean reference source for the regulator...not a current source for your car.

Wire 20B is the generator lamp light for your instrument cluster.

The other two wires at the regulator are the regulated reference voltage to your alternator. Without that regulated reference, the alternator would run at full output at all times...(or not charge at all, depending on the circuit fault.)

As I said in my post, the sole purpose of the voltage regulator is to supply a reference voltage to the alternator, not supply the full current load of the system. Since the heavy currents required for your systems are drawn from main B+ bus of your electrical system at the junction block near the battery where 12R terminates, the 2.4 amp limitation of the LM 317 is therefore not a factor in this installation.

Does this make more sense?


Respectfully,

cbg
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post #8 of 22 (permalink) Old Aug 12th, 07, 12:54 PM
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Re: Stealthy electronic voltage regulator trick

CBG, If I understand correctly, the regulator circuit is (sort of) in parallel, not series, with the accessories drawing load? If so, that would make sense. Since no accessories are drawing load through the regulator, the regulator only needs to draw enough current to have itself function, an amp is likley lots most times then.

If the LM317 is more reliable, then this conversion would be good for anyone, not just restoration/numbers guys then, right?

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post #9 of 22 (permalink) Old Aug 12th, 07, 3:22 PM
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Re: Stealthy electronic voltage regulator trick

From what I understand, you can use a Wells VR-715 electronic voltage regulator cost aprox $11-15 and you can put the stock Delco cover on it.

Seem to me that would be a lot simpler fix.



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post #10 of 22 (permalink) Old Aug 12th, 07, 5:59 PM Thread Starter
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Re: Stealthy electronic voltage regulator trick

Rocks66ss is absolutely correct. I have used the same transistorized regulator...and of course it is fine for the more casual and practical among us. The ones I've seen had riveted on covers, but if you drill out the rivets, you can even swap a Delco cover on there and it looks pretty good. Nevertheless, for the absolute purist, the base of the Wells regulator is not EXACTLY Delco...close but not exact. That's why I posted this whole idea in the "restoration corner" portion of this forum.

If you open up one of those VR715's you'll be shocked how little is in there, and I suppose that you even could rob that regulator chip out of the VR715 and put it in your Delco box, but then where's the fun of tinkering? :-) Plus, you lose the adjustable system voltage feature of the LM317 homebuild. But Rocks is right, the VR715 would certainly work just fine.

______________

Bow Tied, you're very close...but try this. Think of your voltage regulator circuit as an independent circuit, which is monitoring the instantaneous voltage in another circuit, in this case your car's B+ voltage. The regulator then sends a constant message to your alternator telling it to either work harder or to relax, depending on the amperage needs of the moment. So, in that sense, the regulator is a negative feedback control circuit rather than a parallel circuit.

Oh, well...back to the lead :-/ I find that its more fun typing that filing...especially in the Sunny South today.

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post #11 of 22 (permalink) Old Aug 12th, 07, 6:31 PM
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Re: Stealthy electronic voltage regulator trick

Pictures and a sketch would be GREAT.

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post #12 of 22 (permalink) Old Aug 12th, 07, 6:53 PM
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Re: Stealthy electronic voltage regulator trick


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post #13 of 22 (permalink) Old Aug 12th, 07, 8:34 PM
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Re: Stealthy electronic voltage regulator trick

I'm with it now. The IC controls the exitation of the field, and just the field current is what passes through the chip. Am I with it now????

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post #14 of 22 (permalink) Old Aug 12th, 07, 8:56 PM
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Re: Stealthy electronic voltage regulator trick

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post #15 of 22 (permalink) Old Aug 12th, 07, 9:18 PM
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Re: Stealthy electronic voltage regulator trick

Quote:
Originally Posted by rocks66ss View Post
From what I understand, you can use a Wells VR-715 electronic voltage regulator cost aprox $11-15 and you can put the stock Delco cover on it.

Seem to me that would be a lot simpler fix.



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