Adjustable voltage regulator problem

[Meteor53]

Hello.

As a newbie I have to introduce myself and my problem. I'm Kaj from Finland and my hobby is old British motorcycles. They usually have 6V positive earthed electric system with very simple wiring.

I have also Indian made Royal Enfield that has 12V negative earthed wiring with weak alternator so I had to drive without lights every now and then to keep battery charged. Then I bought better alternator and now the problem is overcharging. 15.8V when engine is idling and lights are off. On the road ignition twitches if I don't use high gears and low revolutions.

I have a wiring diagram for adjustable voltage regulator that would work in 6V and 12V positive earthed systems, but not enough skill to tinker it to negative earthed one. I add it here and would be very grateful if someone with better knowledge would help me with this problem.

Best regards, Kaj from Finland

**broken link removed**

PS. If you want translation from finnish, please just ask. One online dictionary is Online English to Finnish to English Dictionary

 

[crutschow]

Well, I can't read Finnish, but, depending upon the current capacity you need, I think you can substitute LM317s or LM350s for the LM338s along with reversal of the diode bridge polarity to convert from positive to negative earth.

(I am somewhat confused though, since it looks like the positive output of the bridge goes to the input of the LM338 when I would expect it should be the negative output of the bridge).

 

[Meteor53]

Wow Carl,

that was fast Like 15 minutes and I have an answer that I have been hunting for two weeks now!

This forum is great. Thank you. I'll get those parts and try alternated diagram.


Best regards, Kaj

 

[stevez]

I purchased LM338 regulators recently expecting the current handling to be somewhat greater than an LM317. I may have been mistaken but if not the 317 might not be a good substitute.

 

[Meteor53]

Hello.

I think that I found the solution myself. LM338 -> LM337, when input changes to negative and then the input from rectifier - . Should work alright?

Fortynately parts are pretty cheap, so I can burn some prototypes

Kaj