Penny Tech (TM) - KTM AC lighting circuit - cheap DC power

[axel99]

Thought I'd add some more to this as I think I may do the same here shortly.

You can also tap into parallel on the output of the Rectifier and run a 30,000 to 50,000 uF capacitor in order to smooth the DC voltage. I think I may have one at home actually and may try this, otherwise you should be able to pick one up at MRO Electronics south of the airport.

There's a lot of good reading here:

http://ktmtalk.com/showthread.php?39336 ... -Tutorial)

http://ktmtalk.com/showthread.php?47967 ... he-Sequel)

The only thing I can't figure out is the ground, Malcolm did you use the brown wire as the input to the eBay rectifier? This seems strange as it should be grounded to chassis.

I am thinking the cap will extend the life of the LED and help you stay above the min voltage required to drive the led when you chop the the throttle for a few seconds. I didn't do the math so don't roast me to badly if the numbers don't support my gut feeling

[Rider Eh!]

http://dirtypart.com/manuals/filer/ktm/ ... l%20UK.pdf

Page 64 has a good wiring diagram that should be the same as the newer bikes.

[Rider Eh!]

Well, to continue on with my own install here are my learnings:

I measured the yellow/red (Reg/Rec DC from stock KTM that normally goes to the digital odometer) and got ~5.5A output with the battery disconnected. I did this out of curiousity to see what that OEM unit was putting out.

Theoretically there is quite a bit of power from this existing DC circuit (50-80 Watts). I'm not sure what the battery requires to charge, but you should be able to run right off of that though you do run the risk of draining the battery.

I added a rectifier which I purchased from digikey (part number GBPC15005) to the yellow wire that normally goes to the headlight as the AC input, and the brown ground wire to the other AC input. I found I got 7.5A output with this installed.

I put a load on the digikey rectifier and found I got 9-15V. So in total we are looking at 70-110W which is quite good and should be enough for grip heaters and a headlight at the same time.

Anyways, I'm going to continue with the yellow AC wire and use the rectifier I purchased and run a capacitor I had laying around from another project to smooth the voltage. My only shortfall here is my capacitor is rated for 16V so let's hope it doesn't burn my bike down if I ever rev it out and let it scream with a current draw.

I noticed when I measured the current the rectifier was getting warm. So I cobbled together an old heat sink to my rectifier from an old computer motherboard I had lying around with my stash of pocket protectors. Made my own bracket, and mounted to my triple clamp. The other bracket you eagle eyed riders may spot here is for my heated grips switch I made previously.

Remember to fuse the input (yellow wire) of the rectifier! 10A should do it.

The only thing that surprised me is when I rev the bike out, the light dims a bit? I haven't been able to explain this yet.

[malcolmzilla]

Cool! My Google fu said about 3.5a off the battery charging circuit, maybe they increased the stator output on the new bikes, I guess I could try to figure out the current meter on my fluke...

[cedric]

Hey Rider Eh!, I'm wondering how the capacitor worked out for you. Do you think it was worthwhile adding it into the mix? Looking to do something similar on my kids' mini bikes and my cabin bomber.

[Rider Eh!]

The one I had didn't have enough voltage capacity as it was rated 16V. I would go with a 30-50V with a 44,000uF capacity. Also wrap that bugger up good with electrical tape or something, mine ended up shorting due to rubbing; it was tucked behind the headlight.

It did work, it smoothed the light and no more flickering, just make sure to do it right! I'm likely going to buy a bigger one and try again.