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motorcycle electronic systems question

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TravisD

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Hey all, names travis and I got a couple questions for you guys

so ill start off by saying im posting here because I read a forum on here about a guy asking if it was possible to rewind his vintage Yamaha stator. well I have kind of the same question, but only a little different, I have a 1975 Yamaha dt250 which came stock with a 2 coil stator that produces 6v AC one for spark and the other to run all the lights ... and I was wondering if it was in any way shape or form possible to rewind this guy into a 12v DC stator ... ive read of this being done, and called all the motorcycle shops around town, and no one has any information .... and or says its not worth it, well I got the bike and the wiring had been completely gutted and the only wires there were, was a wire from the magneto to the coil to produce spark

I do understand that by doing this im going to have to replace all the 6v bulbs and make them 12 v also ... but that's another reason behind this ... Id like to run LED lights all the way around it, here in Kansas when the winter season hits ... it can still be in the 60s and dark before im off work and the standard 6v's just don't appear to be bright enough.

another question I have is, if this is by any chance possible can anyone tell me a way or how to make a chaser circuit design kinda like the new mustangs have for their turn signals ... I have a cool idea for mine and would like them to light up sequintaly

any help would be greatly appreciated guys and gals ... thank you very much in advance
 
It's doable, but it's a lot of by guess and by golly, as you unwind the 6 volt winding, count the turns and then double it, but use a smaller wire to rewind for 12 volts, you might even add 10 or 20% with the idea that you may have to remove some of it when you start it and see what developed. When I did this with a Honda 80, some 30 years ago, the light was AC and the current/voltage was self limiting, you may find the same on your 75 250. As for a sequential signal, do a search here, there was something about it or link for some time back, but it needs DC. Another idea would be to wind your coil so it's floating and has excess voltage, rectify it with one side to ground and capture the energy in a capacitor and feed that into a regulated simple switcher buck circuit. Even easier, if you float the 6 volt and rectify that, you could capture that with a cap and use a switch mode boost circuit light the LT1270a, but you have an output that can supply the current, but since the boost circuit is very efficient, it may work.
Here's a sequential flasher from days gone by
 

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  • Flasher 3-1.asc
    14.2 KB · Views: 324
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Like Kinarfi says: a lot of guessing...

If the original stator winding was intended to deliver only AC to a headlamp, then if you put a full-wave bridge rectifier between the stator winding and the loads, you will lose about 1.6V-2V due to the rectifier forward drops.

Mixing lamps (where one side of the lamp holder is intrinsically grounded to the frame of the bike) precludes using AC for the lamps and DC (using a full-wave bridge rectifier) for other things.

If you rewind the stator for 12V, and you want DC to run 12V headlight and tail light lamps, you will need to add some headroom for the rectifier drops, and possibly use a shunt regulator to keep the voltage from soaring with the lights off. (That is the way most modern bikes, snowmobiles, water toys do it).

If you plan to do your own LED lighting, then single-point regulation of the main alternator output is not needed; you can put the regulation into the constant-current LED drivers on a per LED basis.

If you have a battery on board, a simple charging regulator just for the battery will take care of that, and all of the lighting and other accessories can run from 14V, with no local regulation needed.
 
That .asc file that Kinarfi posted can be opened it LTspice a free program from Linear technology used to simulate circuits.

Kinarfi, do you have a .jpg or pdf to post as well?
 
Firstly, read this extensive thread:-
https://www.electro-tech-online.com...r-for-a-small-motorbike-6v-ac-current.142432/

Among other things it points out that alternators are wound for a specific current, not a specific voltage. If you use LEDs, they are likely to take far less current than the original 6 V bulbs, so the voltage could be very high. The good news is that rewinding is unlikely to be necessary. The bad news is that a regulator of some sort will be needed. If the second coil only runs the ignition, then that part of the circuit can be left alone.

If the circuit is like this:-https://i220.photobucket.com/albums/dd309/makotosun/dt250bwiringdiagram.jpg, then you would also need to change the flasher unit to a 12V one. Transistorised flasher units for 12 V were fitted to most cars from about 1985 - 2000, so are easy to find. However, they will need 2 X 21 W incandescent bulbs to work.

The battery and all bulbs would have to be changed to 12 V, and a regulator would need to be added. I did something very similar to a 1983 Honda CG125, that had an almost identical circuit diagram. I ran a 55/60W 12V halogen headlight in place of the the 25/25W 6 V original.

Also, you would probably need a full-wave rectifier, a smoothing capacitor and another regulator if you run an LED headlight. That could be a bit tricky as both the alternator and the headlight have one side earthed.
 
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This is actually 2 circuits, one voltage source, the voltage to each LED drops as you move from right to left, so each limit resistor would need to different or the brightness would change. To take care of this, I used a current reduction device/circuit, CRD, to keep the current through each LED equal, made up of a JFET and a resistor.
Untitled1.png
 
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  • Flasher 3-3.asc
    6.8 KB · Views: 306
That surprises me, may I suggest you get it, it's so very handy IMHO, so here's the schematic with the current of the LEDs and voltage of the bases. In response to your #8 post, the way this works is the 555 has a period of ~1.5 second and as the voltage on C3 increases, it turns on Q1 thru Q8 sequentially.
Untitled33.png
 
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