Adding DC LED spots to a KTM rally bike AC system.

Andrew and Justin from Team 525 has approached us with the problem of connecting our LED lights to their KTM's. Thier team was going to compete in the Amageza 2015 Rally.

The problem was that the KTM's electrical system is a raw Alternating Current and the Direct Current converter can only provide about 30W. Our motorcycle lights runs from 10-24 Volts Direct Current. The Direct Current converter on the KTM 525's are not designed to power lights.

We decided to get on board and help the team out by getting our in house engineer to build them a small AC to DC converter that will power two of our Premium Mini Motorcycle Spot 10W units directly from the 35w high beam. The concept is simple: Use a bridge rectifier to change the AC from the standard High Beam bulb to DC and send that to the two LED lights. The two mini spots takes 20W total and the halogen bulbs uses 35w. Which frees up 15w of power.

2015-09-02 21.18.06 What you will need: RS Components have a local branch which can deliver most of the items in 3-5 days. Pricey but very convenient

2015-09-02-21.21.14 Tools you will need.
  • Soldering iron.
  • Solder.
  • Side cutter.
  • Crimping tool or long nose pliers

The heart of the system is the bridge rectifier. The one used is totally over specified and can provide up to 15A with ease. The limiting factor will be the 90/100w AC stator of the KTM.  Running two 20w LED lights would also have worked, if we had them in stock but the 10w lights were more than adequate.  Each produce about the same amount of light than the old KTM.

IMG_9019 The bridge rectifier connections: Note that the tabs are cross connected.   

The wires where about 200mm long. Before starting to solder on to the bridge crimp all the wire with lugs and connectors as shown.[/caption] We used lugs  to connect to the bike wiring. That makes it easy to change back to the halogen light if something goes wrong. One of the wires needs to go back to the common tab on the head light for the low beam to work. That is why there are two black wires with both the tab and the receptacle lug. If you don't know how to connect the Deutsch connector provided with the Mini spots watch this video. 

IMG_9021 After soldering the wires to the bridge rectifier remember to add the capacitor. Take note of the positive and negative leads.

The capacitor is also over specified and most likely not needed but it will smooth out any spikes and protect the lights. Place the soldered rectifier bridge in the potting box. Insure that the wires are deep inside the box. That will provide strain relief.

IMG_9027 Before mixing the Epoxy, heat the resin and the hardener by placing the cans in boiling water. If it is warm it mixes well and it is very runny which makes it get in everywhere. In hindsight we should have placed a metal plumbing pipe clip in before epoxying in the rectifier. This would have made it a lot easier to mount the box.

Metal plumbing pipe clip. Found at any hardware store. Hammering it into a rectangle and place into the potting box before adding the soldered bridge and epoxy. Metal plumbing pipe clip. Found at any hardware store. Hammering it into a rectangle and place into the potting box before adding the soldered bridge and epoxy.

Tabs on the back of the KTM main light. There are 3 lights. High Low and common.  The common needs to be connected using one of the black wires. Tabs on the back of the KTM's main light. There are 3 lugs. High, Low and common. The common needs to be connected using one of the black wires.

 How the lights where installed.  IMG-20150815-WA0000IMG-20150829-WA0026 IMG-20150829-WA0021 IMG-20150829-WA0020 IMG-20150821-WA0000 This is the result of having more than double the amount of light. The added benefits is the redundancy which comes from having two high beam lights.


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