Auto voltage regulator

[Doc1590]

I need to build an adjustable voltage regulator for a car. Just a basic two wire, ref voltage/field switch type. The alternator I have has an internal one but it's bad and they want $125 for just the regulator. Being the cheap guy that I am.....
I found an IC that drives a Darlington but there is no schematic etc. The IC is a MC3341 made by "ON semiconductor". Anybody have a suggestion? I nice friendly one?

dave
florida

 

[Hero999]

The regulator will depend on the type of alternator. Normally the rotor winding is PWM'd and the duty cycle is varied depending on the rectified stator voltage. It's a long shot but a switching regulator IC might work, the MOSFET could be connected to the rotor winding and the voltage feedback taken from the rectifier output.

To be honest I'd save yourself the bother and buy one yourself, it'll probably be quite cheap.

 

[power453]

I agree with hero on that one. I've treid to save myself money in the past Doing things like that. Problem is You will end up pulling your hair and teeth out trying to why figure the custom compenents are happy together. By the time I am done with most projects they almost always cost more than an available part.

However, I build most of my own circuits and custom projects of course.

 

[Sceadwian]

Yeah, call more places, find a junk yard or used parts store that carries a new alternator, or regulator.

 

[Doc1590]

You're right, of course.

I've always been a DIY guy and I've spent more money because of it. I'll find a used regulator and just restrict my electronics to my little flashing LED's.

thanks,
dave

 

[Sceadwian]

Nothing wrong with DIY, until you're putting it on the road or otherwise adding human life to the equation =) If some kind of catastrophic accident occurs that can be traced back to your device and it kills someone you're directly liable in many places (that can include murder in some countries)

 

[Aeroplane]

If the Alternator reg is fried it just may be time to get a rebuild or new, I think most of the time just the diodes die have you tested them it may be a cheap fix, but when you open it up check the bearings and brush .

do a google you may find your exact model
**broken link removed**

Have fun

 

[Doc1590]

Nothing wrong with DIY, until you're putting it on the road or otherwise adding human life to the equation =) If some kind of catastrophic accident occurs that can be traced back to your device and it kills someone you're directly liable in many places (that can include murder in some countries)

Yea, that never crossed my mind. That would be horrible. My home made voltage regulator being responsible for something catastrophic? I don't want that responsibility. Now I'm concerned that my blinky LEDs might throw someone into an epileptic seizure. Maybe I just better stay in my room.

dave
(I solved my problem for $12, bought a Mopar regulator and mounted it on the firewall, works great. Holds a nice steady 13.7volts. I guess no one here knows how to make one, but thanks for the intelligent comments, counseling and advice)

 

[CheapSlider]

If this was a system that controls brake or steering then I would definitely stay away.

A car alternator is a 3(4) phase generator with 6(8) diode rectifier and a simple regulator. The regulator monitors the voltage from the alternator and adjusts the current to the rotating field coil to prevent the output rising above 14.6V. The output is a rectified sine wave sliced at 14.6V.

Although the circuit is very simple (Look in the data sheet for L9448VB or L9473) the policy is to replace the entire alternator rather than repair

The hardest thing can be getting to the components inside the alternator.
Modern alternators have all the componets built in. older units may have an external regulator.

Have you checked the slip rings which supply the rotating field coil ?
Are all the mechanical connectors OK?

The only consequence if things go wrong would be that the battery would either overcharge or not charge.

 

[Hero999]

(Look in the data sheet for L9448VB or L9473)

They're probably pretty cheap to buy too.

I can understand it being cheaper to replace modules rather than repairing them but it does annoy me when they start integrating so many modules into one that it becomes very expensive to replace.

 

[demetri]

L9448VB seems like a solution to something i'm working on as well.

Would anyone know where i could purchase? Not sure if they are still available.

 

[RODALCO]

I have built quite a few 12 volts car voltage regulator for alternators with great success, and are still in use 10 years later.
I built hem up in a separate box which i mount on the fire wall.

The wiring goes to the 2 field connectors of the alternator.

The excitation goes as normal via the dash alt. ignition lamp, regulating is done via a zener, two transistors and a 2N3055 power NPN transistor.

It is good practise to replace brushes and check the bearings of the alternator as well.

It was not a cost issue but the challenge for me to built and use this circuit.

Can't see a safety issue here because the car battery will avoid a car stalling with no immideate warning anyway, the alt. ign. light will come on in case a fault occurs.

 

[RODALCO]

https://i123.photobucket.com/albums/o298/RODALCO/DSC01723.jpg 12 volts car regulator

This is the circuit i have used with succes.

Regards

Raymond

 

[demetri]

thanks for the schematic Raymond. i would rather not disassemble it if i can or am i reading it wrong?

 

[RODALCO]

D2, D3 and D4 are usually already in the alternator present.

The rest of the circuit has to be built externally from the alternator.

Probably better for you to get a secondhand alternator from a scrapyard.

Good luck with your project.