head and running light on a 12 volt system

[CroMagnum]

If it's an old single ended (only one wire connection) "dynamo" (really an alternator) you can use a half wave rectifier/regulator. Briggs & Stratton uses these a lot on small engines.

https://www.ebay.com/itm/VOLTAGE-RE...-B-S-691188-491546-793360-794360/331879044399

Just hook the yellow wire to the dynamo and the red wire to battery/lights/etc. Be sure to ground the block to the frame.

Some of the newer 2-connection dynamos like the Tung Lin unit KC posted above look like they put out 12VAC not grounded. In that case you can use the full wave 4-pin GY6-type rectifier/regulator like I posted before. But I also see Tung Lin dynamos with red and black terminals and wonder if they have rectifiers built in. I haven't gotten my hands on any so maybe someone else can throw a meter on theirs and let us know.

Frankenstein has a good point about the output being lower with a regulator. These dynamos are designed cheaply and simply to spit out somewhere around the right voltage while you ride without any fancy or expensive circuitry. A regulated system, OTOH, relies on having excessive output that you can cut down to the proper level.

But keep in mind that these are made to produce full usable output at human bicycle peddling speeds of around 10 MPH. Clamp one of these on your MB and twist the throttle up to 20 or 30 MPH and you really have excessive output and really really need a regulator. Plus you can then hang a small lead acid gel cell on the red wire and keep it charged.

 

[KB_UK]

The 12V ones have two outputs, one 12V the other 3.5V, both grounded to the frame. I don't recommend "half wave rectifiers" as you're throwing away half the power for the sake of ten cents.

From personal experience, a standard 6V 3W dynamo provides more than enough power that regulation and battery charging isn't going to cause a problem. 1W is enough to power an obscenely bright white LED. The serious problem is that such an LED fitted in a normal headlamp reflector is going to blind everyone you ride towards.

 

[CroMagnum]

The 12V ones have two outputs, one 12V the other 3.5V, both grounded to the frame. I don't recommend "half wave rectifiers" as you're throwing away half the power for the sake of ten cents.

If one side of the coil is grounded then you can't use a full wave rectifier. You you have no choice and are forced to go half-wave. It's not about the money, it's about the electrons.

If you could isolate the grounded end of the coil and lift it off the frame then you can use a full wave. Crack open the dynamo, unwind the stupid 3.5v coil, then connect the grounded side of the 12V coil to the other terminal and then you can use full wave and you're no longer throwing half your energy away.

 

[KB_UK]

The dynamo grounds through the frame clamp, just insulating that area with 3 turns of electrical tape is enough. Then attach your AC side "ground" wire to the dynamo's clamp bolt. I do this anyway because grounding through the clamp can be unreliable and damages paint.

I honestly think that sticking to 6V systems is the best option. Bicycle headlamps built to German regulations are very very good. They have proper car-style low beams that focus all the output to illuminate the road, which means their effective brightness is much better because it's not being wasted on lighting up rooftops and clouds.

They're legally limited to 2.4W which doesn't sound much, but they were thinking about oldschool bulbs at the time. With the LED models most sold are .25W to .5W which is comparable to the old fashioned light bulbs of 2.4W. If you ever get to see a full 2.4W German-style LED bicycle light in person you see that they're ridiculously, unbelievably bright, they basically turn the road surface white. They do cost a lot of money though.

With such german and dutch market lights they're going to have built in regulation and a supercapacitor buffer good enough for a couple of minutes operation with no movement, as well as flicker elimination from low frequency AC. USB 5V output is on a fair few too.

http://en.bumm.de/products/dynamo-headlights/lumotec-iq-x.html

This basically solves all of the problems except how to have more than a couple minutes light without moving. For that the Sturmey-Archer battery backup circuit is enough. Just slap three nicads in there and you're done.

 

[Frankenstein]

Well the low beam concept for a bike is pretty cool, basically your/the German government took it seriously enough that they made very specific laws and kept enforcing them, the good ol' Invention is the mother of you know who. Certainly the quality would be on par probably with dot approved motorcycle or moped equipment here in the states, the bike lamps can be fitted with led examples, and even more powerful ones if you have a way to power them.

Perhaps in Germany bicycle incidents/accidents don't happen nearly as often as they do here, people are just simply more aware and used to expecting those types of vehicles on the road, that's the environment. Here in America it seems like I could put a 200 Watt incandescent bulb on the top of my head, powered fully, and STILL people would not notice me. So basically I find that these small things just don't have adequate power for what I want to have lit on a bike.

Cro, I was thinking exactly the same thing, the red black terminal dynos look like they are internally regulated, I can't figure it out, and the descriptions lend hand towards them actually being polarized. I guess the 2 ways they could do that is either actually regulating so they can make cheaper led lights that are cross compatible, or they use using a brushed motor to simply generate dc voltage, if you have the tire spin the knob as they describe then rolling forwards will produce dc voltage at the correct terminals. Since it's led rolling backwards a little bit can't hurt anything since the leds themselves prevent a closed circuit with the poles essentially reversed. The only way to tell for sure is to get one and hook it up to a multimeter, spin a tire (or buffing wheel on a drill) and spin the generator knob, then spin it in the other direction, if the voltage reads negative its a motor, if it stays positive then its an alternator with a rectifier. Thought about reverse engineering a treadmill motor a couple times to make power for my bike.. I have to say the really simple lead acid battery seems to be satisfying everything I need, and plugging it in once a week with normal usage isn't bad at all..

 

[CroMagnum]

Cro, I was thinking exactly the same thing, the red black terminal dynos look like they are internally regulated, I can't figure it out, and the descriptions lend hand towards them actually being polarized. I guess the 2 ways they could do that is either actually regulating so they can make cheaper led lights that are cross compatible, or they use using a brushed motor to simply generate dc voltage, if you have the tire spin the knob as they describe then rolling forwards will produce dc voltage at the correct terminals. Since it's led rolling backwards a little bit can't hurt anything since the leds themselves prevent a closed circuit with the poles essentially reversed. The only way to tell for sure is to get one and hook it up to a multimeter, spin a tire (or buffing wheel on a drill) and spin the generator knob, then spin it in the other direction, if the voltage reads negative its a motor, if it stays positive then its an alternator with a rectifier. Thought about reverse engineering a treadmill motor a couple times to make power for my bike.. I have to say the really simple lead acid battery seems to be satisfying everything I need, and plugging it in once a week with normal usage isn't bad at all..

The problem here is we're mixing old and new technologies that were never meant to work together.

Bicycle "dynamos" are really just permanent magnet alternators. But they weren't designed to stand alone. Rather, they're part of a system that includes the expected speed of the bike, internal resistance of the coil, and the temperature characteristics of the bulb filaments and a very specific load.

This is why you see them all listed as 6V 3W, because the coil resistance helps limit the current when the voltage raises. Plus the resistance of the bulb filaments go up when they burn hotter, so it's kind of self regulating. And you have to run these specific bulbs at 6V 2.4W (headlight) and 6v .6W (tail light). If for some reason you're not running the tail light, then you have to change over to a 3W headlight bulb to keep things working properly.

So you take this crap left over from the 1960s (really it dates back to the 1920s) and try to marry it to modern technology. Incandescent bulbs don't care about AC or DC, but LEDs do. And the LEDs are not nearly as forgiving about voltage without a lot of added circuitry. Plus batteries can't deal with AC and have very specific charging requirements. Now you add in the fact that some modern dynamos have rectifiers to supply DC, with zener diodes to clamp the output voltage and it all gets complicated.

That's why you need to get a specific model and take it apart to see exactly what they're doing before you can start using it for anything else besides the standard bulbs. Personally, I'm a believer in keeping things simple and modular. If I was using one of these, I'd get rid of secondary 2.5W winding along with any internal rectifiers or zeners, and just output simple 2-terminal ungrounded AC, then feed that into a moped regulator. After that you can pretty much hook up anything you want.

 

[KB_UK]

As I said before the European market is littered with very good LED lights for dynamo power, from the cheap "be seen" ones to €100+ instant daytime devices, and you can get them anywhere from the internet. How to hook up a rechargeable battery is also well understood, posted that circuit in here for everyone. Don't overthink it.

Really and this is the key thing, if you're into dynamo power for more than just sheer cheapness (a basic full set is €10) or novelty value, you should really go with a hub model. They cost a lot more but you really don't want a tyre dynamo when it's raining, they slip terribly.

 

[Frankenstein]

As I said before the European market is littered with very good LED lights for dynamo power, from the cheap "be seen" ones to €100+ instant daytime devices, and you can get them anywhere from the internet. How to hook up a rechargeable battery is also well understood, posted that circuit in here for everyone. Don't overthink it.

Really and this is the key thing, if you're into dynamo power for more than just sheer cheapness (a basic full set is €10) or novelty value, you should really go with a hub model. They cost a lot more but you really don't want a tyre dynamo when it's raining, they slip terribly.

I don't want a dynamo, I want an alternator lol.. This bullet train has some basic form of one, and not even settled if I'm using that motor. Could pull it and do a reboot.

 

[KB_UK]

Well there's 12V coils out there for the regular china motors, plus an actual belt driven alternator on this

 

[Frankenstein]

Yeah, that's the type of thing I'm talking about, something that makes a decent (for a bike) level of power you can use to keep a decent battery charged while running acceptably bright lights.