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Discussion Starter · #1 ·
Hi gents. Since the normal rectifier/regulator is inferior and also expensive. I do some research and find the micro controller controlled SCR rectifier/regulator is very promising. I'm electronic noob but I believe it play with the SCR duty cycle so this way it don't have to sink the unused current back to the alternator the whole time so it should cool the whole system down quite nicely. Attached is the schematic principle.

Now to the questions.

1. Is it ok to use pwm pin on Arduino to control the SCRs to get the desired dc voltage?

2. What is the appropriate regulator circuit to use? If the uC works so well to get to the desired dc voltage (say 13.8v to prevent gassing), can we just put the capacitor filter in? (maybe 4700uF/35v would do the job?)

3. I would prefer the charge warning light (as my m900 has one on the dash) but seems like nowadays the new regulators take this function out. I can't find any circuit with it so if you could point me to?

4. Can't figured it out why they use steel heat sink instead of aluminium lol.

I'm very open to any of your thoughts/ improvements would highly be appreciated.
 

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You say your an “ electronic noob “ but you’re attempting this ? That makes no sense.
 

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As I understand it the regular regulator/rectifier uses scr already so you would be reinventing the wheel. Moffset regs run cooler and are also available.
Manufacturers have spent considerable time and money with teams of electrical engineers to develop the Regs that are commercially available.
 

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Discussion Starter · #4 ·
That's my first thought. First I searched for the motorcycle regulator and can see they also use scr to control (pls correct me) the excess current back to the alternator. When I looked closely it was just totally different concept. The typical rectifier use diodes which work full time minus the current sink by controlled scr. This means the system works full power on full time hence the immense heat generated. I also have a look on the mosfet circuit and IIRC it is on the same basis. Then I came across this and I think it is the way to go as it works as much as it needs no matter how much the voltage sent from the alternator.

I think I'm not reinventing the wheel here but just try to improve it. I would love to see graphene wheels in the future. :)

You say your an “ electronic noob “ but you’re attempting this ? That makes no sense.
A noob may be a bit too optimistic for me. Let's say if we can get to the right circuit, I have more than 50 percent chance of success making it to work. :D
 

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I used too think the same, ie any excess current is shorted to earth causing lots of heat and extremely inefficient. This is wrong however, the short is on the A/C side and shorts the diodes in the rectifier. This means there is no DC output, the current simply goes back and forth through the stator and actually creates very little heat and uses almost no engine power. The heat created in the regulator/ rectifier is when it is flowing power to the battery and is due to the resistance in the diodes and scr. Moffset regs have lower resistance than scr so run cooler.
The key to understanding how the system works is to realise an alternator is effectively a electron pump and to convert a/c to d/c requires two one way valves ( diodes) , one is an inlet valve one is an outlet valve. If one of these valves are held open ( shorted diode) then no output will result.
 

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Btw, car/truck rectifiers also get hot for same reasons as above but have sizable heatsink and a fan to blow air past for cooling. Motorcycle rectifiers tend to be smaller, have no fan and are often mounted where there is no airflow.
 

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Discussion Starter · #7 ·
Thanks for your info. Haven't had a look into car/truck reg/rec though as they re working fine but it would be interesting to see the design/sch. Still trying to figure it out why bike reg/rec heat sink is made of steel. I might replace it with AL sink with an automatic fan on.

I used too think the same, ie any excess current is shorted to earth causing lots of heat and extremely inefficient. This is wrong however, the short is on the A/C side and shorts the diodes in the rectifier. This means there is no DC output, the current simply goes back and forth through the stator and actually creates very little heat and uses almost no engine power. The heat created in the regulator/ rectifier is when it is flowing power to the battery and is due to the resistance in the diodes and scr. Moffset regs have lower resistance than scr so run cooler.
The key to understanding how the system works is to realise an alternator is effectively a electron pump and to convert a/c to d/c requires two one way valves ( diodes) , one is an inlet valve one is an outlet valve. If one of these valves are held open ( shorted diode) then no output will result.
You got it almost right. As the resistance in an alternator will be relatively low compared to the reg/rec, it will subjected to a lot less heat. The normal reg/rec, on the other hand, if working full time, have to get rid of excess voltage/current in terms of heat. If some people say it was around 3phase 70vac from the alternator at 5000 rpm, got this down to 14vdc full time will be quite a lot of heat. The mosfet runs cooler and it has a negative temp coef. when it gets hot, its current drops but working on full time basis I think there will be more room for improvement. ;)
 

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Your best bet to improve the reliability of the regulator/rectifier would be to add some airflow either by relocating to a better position or you could add a small fan like a 12v computer fan.
 
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