Automotive 6 Volt Generator Transistor Voltage Regulator

[Danwvw]

Not to stray too far here, I put new bearings and brushes into this Motorola Alternator back in 2013, It may have blown a diode though a couple of years ago as my dome light seems to have a rapid rpm related blink near idle: It's not so easy to remove one of these from the car because of the engine cooling fan running off one end of them. I should pull it off though and change the diode but it still keeps the battery up fine.

 

[KeepItSimpleStupid]

If the engine runs, put a scope on the battery while it's running. It will show up like a sore thumb.

 

[Danwvw]

I should try that!

 

[KeepItSimpleStupid]

Ac coupled. Look at ripple.

 

[Danwvw]

Yeah, I was thinking, since it's the rainy season of setting inside the VW Bus with the scope and looking at the ripple at the Dome light.

 

[Danwvw]

Here is a Idea for a Adjustable Regulator using the LT6700, I have found a SOT-23-6 BreakOut board for a DAC with mounting holes I can use to make the prototype easier to build.

 

[KeepItSimpleStupid]

You don;t need all of that front end stuff.

try the following:
make r1 =180K
make the potentiometer 20K
make r2=13K

Loose the th451 and the 150 ohm thing
Adustment should be 5.4 to 8V

They might not be standard values.

 

[Danwvw]

Huh? That wouldn't work! (Only would have 37ua, it would be noisy) I think I see where you are coming from though and I have already been there. (We discovered using a zener to measure the generator output voltage provides a more stable operating generator output.) Probably The 150 ohm should be 15 ohms though to get the TL-431 IKA current up a little more The TL-431 operates between 1-100ma sink current and 15 ohms is 26ma at 8 volts. Remember the voltage drop across the input to ground is never going above .4 volts regardless of the circuit used here. But yes the input network could be just resistors or it could be just a 7 volt zener and that 15 ohm resistor for a fixed regulator voltage. Considering A TPS3700 Window Comparator instead of the LT-6700 because it has higher Temperature ratings. The Voltage Regulator area in the car gets up to about 155' F. maybe even more at times. Thanks for the comment.
Actually my TL-431 References are type C which are rated for only 70' C So I will use a 47 ohm resistor to keep the current through it below 10ma. The 150 ohm would give 2.6ma still enough it would work maybe better since the TL-431C is being used.

 

[KeepItSimpleStupid]

85C = 185 F

150C = 302F

depending on the part.

 

[Danwvw]

Actually Other components are marginal including the STPS40L15's I think I may have seen one lock on once with the key off after having the headlights on. As a component they read a lot lower forward bias voltage on the meter diode check after having been in service. With the Head Lights on The STPS40L15's are close to maximum 40 amps and in fact If the battery is low they may need to handle 50 amps or even more. (One reason I like the current limit designs but they wouldn't current limit well enough to stay below 50 amps without introducing considerable generator output voltage drop with the headlights on. It's an area that needs more testing the LM393 design may have helped that, it's better but I don't have an Amp Meter on it's prototype.) The STPS40L15 heat sink I have been using is just the B+ Terminal on the Old Mechanical Voltage Regulator base. It's a pretty solid piece of copper and it can transfer some heat back up the 2 big wires that connect to it but it does heat up to 155' F about 70' C. Its forward voltage drops with temperature > which helps too. The early LM 317P design would output a climbing voltage with how hard I drove, about 200mv or so Voltage >. I don't seem to see that happening now with the LM393 design in the car though.

 

[Danwvw]

Been waiting on parts, storms let up, took the car out for a drive today. LM393 Voltage Regulator Design is working nicely with 7.0 volts up front and 6.5 volts with the Headlights which cause enough heat in the STPS40L15 Cutout Diode to raise the 7.0 volts to 7.13 volts when I turn off the lights but over a minute or two it cools down and the voltage up front goes back to 7.0 where it is adjusted to run.

More on my mind lately is A Engine Temperature Circuit if anyone is interested.

 

[Danwvw]

The LT-6700 chip and its SOT 23-6 BreakOut board arrived and here is a Mock-Up of the Prototype. Note a 1K 10 Turn Voltage Adjust Pot is located on the underside accessible through access tube.

 

[Danwvw]

 

[Danwvw]

OK, Just tested and with slight modifications LT6700-1 Prototype is Bench Testing fine. The low side resistor on the Voltage adjust was changed form 1K to 200 Ohms this design still has a very wide range of voltage outputs from below 6 to all the way up Past 12 volts.
Here is the UpDated Schematic:

 

[KeepItSimpleStupid]

Is there any quiescent current when it's not active? i.e Ignition off?

Any current limiting planned? e.g. Use a hall effect sensor or say a GM battery sensor on the battery cable.

 

[Danwvw]

The LT-6700 is powered all the time due to the anode / cathode of an 1N5817 diode supplying it, but it's just 12 ua. Also the counterpart 1N5817 RT is reversed biased and will have some leakage. Then The STPS40L15CW cutout diode will be hot sometimes and leak worse than anywhere however I have been testing them on the car now for a year and the battery is staying up nicely for weeks! I think measuring "would" be worth doing.
"KeepItSimpleStupid" Show me the Current Sensor you have in mind!

 

[Danwvw]

Proposed Hall Effect IC current Limit Idea using a ACS773LCB-050B-PFF-T Hall Effect IC and the unused Non-Inverting OP-Amp in the LT-6700-1

 

[Danwvw]

Thinking of the best easy way now to modify an old mechanical 6 volt voltage regulator and I realize that using a breakout board for the Comparator OP Amp IC would eliminate a lot of the difficult soldering, the LT-6700-1 is only available in the TSOT-23 IC which is a Surface Mount part, very difficult to solder in. So I want to come up with a Break Out board that already has a OP amp on it. If a design can be done that uses a ready made breakout board, then anyone could make their own voltage regulator with hand tools like a Drill and a Dremel tool and a Soldering Iron and some hardware and wire. Currently considering the LM358 Board, Anyone have any experience with these?

 

[Danwvw]

SparkFun has a nice OP amp BreakOut Board but it has a TSH-82 on it and I am not sure these OP amps would be suited to the task of a Comparator?

 

[Danwvw]

Thanks ahead for your post

and "KeepItSimpleStupid" for. the links and Ideas. I have some of this on order, say "KeepItSimpleStupid" my wife is an artist if you would like a sketch of some kind for your profile I wouldn't charge you. It's Just the "K" is a little impersonal and the handle says a lot but I feel like I am telling everyone they are stupid when I use it in a quote.