GX390 charging coil question

Rapidrob

Well-Known Member
#4
I'm just curious, I see the single wire coil does in fact have one leg of the coil soldered to the iron core which will short to ground when bolted down in the block. If un-soldered and a wire added would this make the coil a two wire coil as shown in the above link?
 

chrisr

Active Member
#5
Would it be possible to take two single wire charging GX390 coils and add a diode to remove the AC/convert to DC and a capacitor to smooth out the pulses? The two wire coil is a lot more money vs. two single coils and the factory GX390 rectifiers seem pretty pricey.
 
#6
sure a couple of 1n4007 Diodes a 1000MFD cap and your in business. That is the way the lighted Tecumseh's are changed to use DC led lighting. Here is a circuit board I mounted in a small project box for my Rupp Continental which used led lighting.
 

Attachments

#8
sure a couple of 1n4007 Diodes a 1000MFD cap and your in business. That is the way the lighted Tecumseh's are changed to use DC led lighting. Here is a circuit board I mounted in a small project box for my Rupp Continental which used led lighting.
Wow what are all those vacuum tubes for?
 

chrisr

Active Member
#9
sure a couple of 1n4007 Diodes a 1000MFD cap and your in business. That is the way the lighted Tecumseh's are changed to use DC led lighting. Here is a circuit board I mounted in a small project box for my Rupp Continental which used led lighting.
Do you have a wiring diagram you can share on how the wires and components are soldered together on the circuit board? Would each single wire coil be married together as one wire and then soldered to the board?

Thanks
 
#10
Why not a full wave rectifier or is that overkill?
Because as Dave had educated me the two coils are on the tec are not phased either together or 180 apart it winds up heating the coils but using half wave does not cause that issue. Also the common ground also causes issues with full wave rectifiers if the case is grounded.
 
#12
Do you have a wiring diagram you can share on how the wires and components are soldered together on the circuit board? Would each single wire coil be married together as one wire and then soldered to the board?

Thanks
I’ll look but each wire from each coil goes to one diode then other side of diodes are tied together along with + lead of the cap and that will be the positive dc lead. The negative of the cap goes to frame ground.
 

Rapidrob

Well-Known Member
#13
Thats where I was looking at the one coil wire that is soldered to the iron core. I was wondering if the wire could be removed and a 2ND wire soldered to it and run out with the original single wire?
 
#14
Thats where I was looking at the one coil wire that is soldered to the iron core. I was wondering if the wire could be removed and a 2ND wire soldered to it and run out with the original single wire?
Probably you would remove it from the core then us a meter and check to make sure there is no continuity between removed coil wire and core.
 

Rapidrob

Well-Known Member
#16
OK, I just ran several test on my Trail King MB that has the twin single wire coils. The engine idles at 650 RPM and maxes out at just over 3,000 RPM by a stop.
I started out with the engine warm, and idling.
Here is the idle AC output:
FW1.jpg

At at max RPM for my engine:
FW2.jpg
As you can see, even if running to an AC head light bulb, this would mean death to the bulb in very short order. The rising and falling VOLTAGE would be very hard on the filament as Ohms law states.
Now running through A 30 Amp Full Wave Rectifier ( 5-50 volts rated) You can see the slight drop in voltage as expected due to the Diodes firing at idle:
FW3.jpg
A now at max RPM. As expected the voltage is way too high for a DC bulb and will burn it out as well:
FW4.jpg

Now for something no one ever talks about Hertz. This is how many pulses of energy per second is being generated,both positive and negative pulses.
If you live in the USA the Hz are 60, and most of the rest of the world is 50 Hz. ( 120 pulses in the USA / 100 pulses outside the USA per second)
Now since the engines flywheel,if you have the Lighting flywheel with three magnets, changes speed as the engine speeds up, the Hz are uncontrolled.
These pulses are going through the bulbs filament and vary with engine speed. ( think firing a single shot shotgun to pulling the trigger on a MiniGun. One shot per second or 100 shots per second) It's no wonder bulbs fail so fast if un-regulated. an expensive lesson to learn.
Now lets look at the wave form on a O-Scope. I have combined both legs of the single wire coils (2) and grounded the probes to the engine chassis.
As you see off to the right of the display we are getting some sort of distortion. While this may be called noise,what you are really seeing is the development of Counter Electromotive Force or EMF ( not EMP that's in nuke weapons going bang) This is a force countering the voltage and current being generated by the faster and faster spinning magnets. It is what governs electric motor RPM's by design.
Anyway, it too is not a good thing for light bulbs as now the filament has to deal with this noise as well.
So far we are just looking at the AC output. Now it has to be rectified to DC and then regulated to prevent an Over Voltage.
Here are some O-scope displays on various voltage settings:
FW6.jpg
FW7.jpg

Engine is running at 2,800 RPM
FW9.jpg

OK, now that you a bored to tears, lets run the varying AC from the coils through a Rectifier and Regulator. The rectifier changes AC to DC, the Regulator does all the magic You need to know about. It keeps a constant VOLTAGE ( at normal running engine RPM) to your lights or Cell Phone charger,etc. It also keeps a constant current ( amps) to the devices as well. How it does this is very complicated. In the US Navy we called this PFM.
( Pure Fuc%&*g Magic) Just know that it does work very well.
OK, so the new Harbor Freight LED Spot Light is hooked up to the Rectifier/Regulator and the engine is idling.
FW11.jpg

As you can see it is too low to run the LED head Light at maximum brightness. Adjusting it here at idle MAY,depending on how well the device regulates provide way too much voltage at max RPM and burn out the LED's. I like to adjust at the "normal" running rpm which on my engine is about 3/4 throttle. You decide what you want to do. The regulator does a pretty good job of keeping the voltage to 12VDC or so.
I will re-adjust to 13.0 VDC as most car batteries provide that under load,perhaps a little more. By adjusting to lets say,13.5 VDC,you will never hurt the LED's but get max brightness and a little more Current to power other lights,cell phone charger,etc as well.

FW15.jpg

FW13.jpg

Now what about the killer HZ? There are none. The Rectifier/Regulator provides pure D.C power. 'It don't get no better than this.
FW12.jpg
Here is the LED Head Light running at 2,500 RPM and the Rectifier/Regulator is doing it's job very well. The head light is bright with no flickering what so ever. Current ( Amps) was just under the rated 1.25 ( one and a quarter).
The Rectifier/Regulator even,through stored energy in the large capacitor ( large black can looking thing) kept the Head light on full brightness at idle for over 5 seconds! then it dimmed down to about 1/3rd output,still enough on a dark night to be seen by others. A slight increase in RPM brought the Head Light up to full power again. By adding a battery/ battery pack the HL will stay at full brightness.
The Heat Sink never go over "warm" to the touch after a ten minuter run at high speed ,full load.
At idle it stayed cool.
I hope you found this info helpful in using the power your Flywheel and coils addition you have done to your engine.
There is a lot of helpful info here from others as well. Use what you think is best for your devices you wish to power.
This is what woks for me.
FW14.jpg
 
#17
I like that unit you found! One question when you were testing the ac output was it unloaded? (IE no bulb or equivalent resistance)?
 

Rapidrob

Well-Known Member
#18
I did Sir. There was only about a 3.5 VAC drop under the load of the new LED Spot light. With a incandescent bulb, the initial drop was about 5 volts and then it settles out to about 3.5 VAC when the filament was under a stable load. This of course is dependent on engine RPM and the rating of the coil/coils under the flywheel.
There is a device I think is called a Varistor (in reality a current limiting device that you can place in line to the bulbs leads that gives the bulb a "soft start" and a slow off.) I used those at work for decades and they saved lamp filaments by tens of hours of on-time.
 
#19
I did Sir. There was only about a 3.5 VAC drop under the load of the new LED Spot light. With a incandescent bulb, the initial drop was about 5 volts and then it settles out to about 3.5 VAC when the filament was under a stable load. This of course is dependent on engine RPM and the rating of the coil/coils under the flywheel.
There is a device I think is called a Varistor (in reality a current limiting device that you can place in line to the bulbs leads that gives the bulb a "soft start" and a slow off.) I used those at work for decades and they saved lamp filaments by tens of hours of on-time.
This is great AC info for me thanks for that
 

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