Suppose I build Alec_t's circuit and it works and then I want to encase the circuit in an epoxy type resin to waterproof the circuit for use on a motorcycle where moisture could be an issue....

I've seen CDI modules and other electronics encased in some sort of resin (epoxy?) for that purpose.

Any suggestions?

I would make one side of that epoxy mass a big, fat, finned heatsink and screw the SCRs (with appropriate electrical insulation (silicone or mica patch)) to the heat sink. A small project box can be the other five sides.

 

Why not change the AC voltage to DC and regulate to a suitable DC voltage of around 10vdc. The headlights aren't going to mind being powered by DC as opposed to AC.

 

Why not change the AC voltage to DC and regulate to a suitable DC voltage of around 10vdc. The headlights aren't going to mind being powered by DC as opposed to AC.

Much of the system was designed around being AC powered but you might have a good point?

Since we're dealing with 6V and the limitations of the magneto, I thought it might be because by the time you convert from AC to DC, you'll lose enough voltage to make it hard to power the headlight......but I'm not sure.

 

Hello folks,
I need a 6V, AC, 5Amp voltage regulator. Maximum current "should be" 3Amps at any time, so 5Amps as a safety margin.
This shouldn't be difficult right?

I can't seem to find one so I was thinking there probably an easy way to make one.

Can anyone guide me along? Best direction to go?

Actually, the input voltage can vary but the ACTUAL voltage after regulation needs to be 7.2v +/-

I said 6v because it is a 6v system

Thanks

Some light weight Japanese motorcycles used a bidirectional AC Zener shunt regulator, but the cheapo AC lighting system probably didn't continue on more recent models - and service spares "black box" units tend to be a bit pricey.

The TL431 application note shows how to boost current by adding a power transistor - enclose that in a bridge rectifier, make it adjustable so you can trim out the diode Vf.

 

Alec_t,
In your circuit, it looks to my novice eye that the 1N4148 diodes will be exposed to the full current from the source?
1N4148 diodes are VERY low amperage diodes. My application will generate up to 5amps.

Will this circuit with those 1N4148's be ok with 5 amps from the source?

 

Why not change the AC voltage to DC and regulate to a suitable DC voltage of around 10vdc. The headlights aren't going to mind being powered by DC as opposed to AC.

Because with a typical motorcycle permanent-magnet alternator, the AC voltage can go very high if it is not limited by some means, possibly high enough to damage the winding insulation.
Thus the voltage is clipped or clamped to the desired voltage.
Both AC and battery systems typically use that method.

 

it looks to my novice eye that the 1N4148 diodes will be exposed to the full current from the source?

Your eyes need retuning.
The diodes are back-to-back and only carry the small current through the gate resistors.
They are fine for that purpose.

 

Much of the system was designed around being AC powered but you might have a good point?

Since we're dealing with 6V and the limitations of the magneto, I thought it might be because by the time you convert from AC to DC, you'll lose enough voltage to make it hard to power the headlight......but I'm not sure.

A DC regulator can be used to keep the voltage at it's lowest level before drop-out due to low RPMs. The that voltage can be put through a DC to DC boost regulator up to the desired voltage to illuminate the lamps. A little more complicated, but it should work ok.

 

A DC regulator can be used to keep the voltage at it's lowest level before drop-out due to low RPMs. The that voltage can be put through a DC to DC boost regulator up to the desired voltage to illuminate the lamps. A little more complicated, but it should work ok.

But the input from the magneto is AC ?

 

A DC regulator can be used to keep the voltage at it's lowest level before drop-out due to low RPMs. The that voltage can be put through a DC to DC boost regulator up to the desired voltage to illuminate the lamps. A little more complicated, but it should work ok.

A dc-to-dc boost regulator is not going to make more watts than the alternator is producing at low rpms. Motorcycles and cars usually just suffer from brownout conditions (or rely on the battery) when idling or low rpm operation. No reason for the added complication of a boost regulator.

 

A DC regulator can be used to keep the voltage at it's lowest level before drop-out due to low RPMs. The that voltage can be put through a DC to DC boost regulator up to the desired voltage to illuminate the lamps. A little more complicated, but it should work ok.

If its the generator on a small motorcycle; you have to be careful! - They vaguely resemble current sources and the voltage can get silly on light loads.

Most small motorcycles just had a ballast resistor for when only running lights (a few had posh AC Zeners as I mentioned in an earlier post) its pretty much balanced to the PTC characteristics of correctly rated bulbs.

At low RPM it can't do much damage, at high RPM; the inductive reactance of the generator windings starts getting more significant.

The best plan might be to let the generator find its own voltage at low current and use a buck regulator - but I haven't proven that theory.

 

If its the generator on a small motorcycle; you have to be careful! - They vaguely resemble current sources and the voltage can get silly on light loads.

Most small motorcycles just had a ballast resistor for when only running lights (a few had posh AC Zeners as I mentioned in an earlier post) its pretty much balanced to the PTC characteristics of correctly rated bulbs.

At low RPM it can't do much damage, at high RPM; the inductive reactance of the generator windings starts getting more significant.

The best plan might be to let the generator find its own voltage at low current and use a buck regulator - but I haven't proven that theory.

Aren't devices that generate DC current called Generators and those that make AC current called Alternators?
Because the talk of generators here is a bit confusing when the subject is alternating current.
Again, please take this with a grain of sugar as I'm asking....

 

Aren't devices that generate DC current called Generators and those that make AC current called Alternators?
Because the talk of generators here is a bit confusing when the subject is alternating current.
Again, please take this with a grain of sugar as I'm asking....

Both make AC - the difference is in the design.

http://www.differencebetween.net/object/difference-between-alternator-and-generator/

 

Aren't devices that generate DC current called Generators and those that make AC current called Alternators?
Because the talk of generators here is a bit confusing when the subject is alternating current.
Again, please take this with a grain of sugar as I'm asking....

Traditionally; a dynamo is DC because the commutator and brushes always keep the armature windings right way round.

Alternators usually have the generator windings on the stator ring, the rotor can be permanent magnet, rotating field winding with slip rings or co-axial magnetic pole coupling.

a flywheel generator usually had 2 or 3 bar solenoid windings arranged within magnets on the inside diameter of the flywheel - the later so called "spider" stator blurred the definition a bit.

"generator" is widely used as a generic term.

 

Is the AUIRF prefix the same as just IRF?

The same. IRF3205 should suit, but bear in mind its mounting tag is also the drain connection.
There are so few components in the circuit I posted that you could do without a circuit board and use component-to-component wiring.
Do not embed everything or it will cook! I'd just cover any bare wire/joint with a heat-resistant conformal coating (silicone?). Finned heatsinks of appropriate geometry would be reasonably weather-resistant and could be fixed together to provide mechanical protection for the components. All wiring will need vibration-resistant support.

 

Will this circuit with those 1N4148's be ok with 5 amps from the source?

Yes. They pass only a few mA for driving the FET gates. The FETs drain-to-source paths do the heavy lifting.
The circuit will work whether the input is 6V, 12V or 50V! The higher the input voltage the greater the voltage that the FETs drop and hence the more heat they create.

 

Thanks Alec_t

VERY helpful info. I've ordered the parts to assemble the regulator. I'll post back after the parts all arrive and I've had a chance to give it a try.

Thanks again for your help and Best Regards,

Lumenosity

 

Why not use a variac that is turned by a servo controlled by the battery? Actually, try converting it to DC and using a DC-DC regulator. Maybe have zeners to prevent extreme overvoltages.

 

Alec-t,
Thanks again for posting the schematic.
All the components have arrived today so I'll be building and testing your design soon.

Will post back on the results.
Regards,
Lumen

 

Alec put a lot of effort into that elegant design and the TS was really happy with the result. The problem with the MC is making it small.
But IP65/IP67 cases are available http://www.twinner.com.tw/files/gainta/G1XXMF SERIES.pdf has a 64 x 58 x 35 mm enclosure which still could be too big.



A search for "Debe atom" should reveal some interesting construction techniques for building a solid state ignition module. No PCB was required. He starts with some Aluminum "C" channel. That technique might work for you. That design could be "potted" with some electrical grade silicone. The electrical grade doesn't have acetic acid in it which will corrode parts. Three unsupported sides. If you want to form the sides get some Teflon or bondable Teflon (usually about 0.005" thick with an etched surface that can be epoxied) They can be removed after the silicone sets.

Here https://www.rshughes.com/p/Loctite-...nd-Paste-300-Ml-Cartridge-40088/079340_40088/ is an expensive version.

This https://www.rshughes.com/search.html?q=locktite+si5011 should work too. It's a milky white when dry.