Solid State Voltage Regulator Conversion

[MGTF1250Dave]

Aloha,

I am considering converting a mechanical two spool Lucas voltage regulator to a solid state electronic regulator. I would have the job done by someone who does this professionally. The one I would have converted is not operable. Does anyone have experience operating with this conversion?

 

[Adrio]

I have made one and it worked just fine. Though my only use was for the electric temp guage in my TR3. That car was suppose to have a mechanical (either bulb) guage but I only had a early TR4 electric one. What i did was put the sender in a pot of water on the stove and got the resistance vs. temperature figures for it. Then I set up a bench test for the guage itself and got a current vs. temperature reading curve for it. Combining those two curves I was able to determine what the voltage of the regulator had to be. I am at work now (no comments) so I can't get you the value it worked out to (was many years ago) but I do remember it was an even value or at least a normal value as I was able to build it with a single unit three pin voltage regulator chip 9and positive ground to boot). If you want the values I can look them up for you this weekend. Just PM me (or do a search on here I may have posted the results way back when).

 

[angelfj1]

Aloha,

I am considering converting a mechanical two spool Lucas voltage regulator to a solid state electronic regulator. I would have the job done by someone who does this professionally. The one I would have converted is not operable. Does anyone have experience operating with this conversion?

Hello Dave. Just to confirm, are you thinking of retaining the Lucas dynamo or converting to an alternator. Here's and example of a solid state replacement for the Lucas "box". Not expensive at $80.

solid state voltage regulator

Of course, modern alternators have internal solid state control for excitation, so the "box" would not be required.

 

[MGTF1250Dave]

Aloha Adrio,

Thanks for the reply. I have rebuilt a 10VDC voltage stabilizer for the Temp and Fuel guage as you describe. I guess I didn't make it clear I was asking about the Dynamo/Battery voltage regulator or control box. This is a conversion of the Lucas RB106 control box to a solid state electronics.

P.S. I found a source for the three pin stabilizer but I have to look at home for the website address. I think they were about $1 to $2 each.

 

[MGTF1250Dave]

Aloha Frank,

I was planning on keeping the Dynamo. Your link is to where I was planning to have the conversion made. Seems to me I would eliminate points in the control box arching and sticking. I can retain the original look and have a replacement with no moving parts.

 

[TR3driver]

Seems to me I would eliminate points in the control box arching and sticking.

Even more important IMO, eliminate overcharging when the load is light, and undercharging when the load is heavy (headlights on). Of course, you could also do that by converting to a 3-bobbin unit, like the one used on Vitesse, Spitfire and I believe GT6.

Shame you're not doing it yourself, as I think it would be an interesting DIY project. But please do keep us informed of how it turns out!

 

[MGTF1250Dave]

Aloha Randall,

I know enough about electronics to know I need help. As Harry Callahan said, "A man's got to know his limitations". I know I can not solder components to a circuit card. I'll let everyone know if it works out.

Another reason I am thinking about this is that I can use the carcass of the car's original Lucas Control Box.

 

[Sarastro]

I think this makes a lot of sense. I was going to do it with my Bugeye Sprite, to preserve the original appearance and not have to modify the tach. I had actually designed the thing and started testing it (I'm an electrogeek), but eventually I just switched to an alternator.

That mechanical regulator, you have to realize, is really crude. The simplest electronic regulator should be way better; it would be hard to do worse.

One consideration that was a dilemma for me: the transistors in the regulator handle a fair amount of power and therefore probably generate a lot of heat. There has to be some way to get rid of it. Clamping it into that bakelite box is prevents the heat from escaping. You might ask the maker how he handles the heat sinking.

 

[angelfj1]

Dave: Great. Please keep us posted. I may want to make this conversion at some point in the future.

 

[TR3driver]

You might ask the maker how he handles the heat sinking.

If you zoom in on the photo on the website referenced above, I think you'll see an aluminum plate mounted vertically that serves as heat sink. The field control is undoubtedly done with a power MOSFET for minimum forward resistance; and of course operates in switching mode to keep power dissipation to a minimum.