My Cateye ABS Halogen to Cree LED Project

 

There are 2 forum threads for this project. 1 on the Candle Power Forums HERE and 1 on Singletrackworld HERE

The starting point for the project is a set of cateye abs 35 lights. The end result I’m looking for is 2 sets of lights that will be suitable for mountain biking on the trails here in North Wales

The starting point

Cateye ABS 35
Batteries = 2 x (6 Volt 3000mAH) = 36 Watt hours
Low = 15 watt flood = 2.4 hrs
Med = 20 watt spot = 1.8 hrs
High = 15 watt flood + 20 watt spot = 1 hr
Weights
Cateye abs 35 = total 1.15kg (approx)
2 x batteries = 0.75
2 x head units inc bulbs = 0.25kg
1 x cable set = 0.15kg

The bulb holder is the key element in this and here are a couple of photos

 

The plan is to split the system in two and create 2 lights from it. I’m intending to use the Cree MR11 from Cutter with the Maxflex driver.

Each light system will be like this

here’s an incredibly dodgy drawing that shows how the led’s, optics and driver should sort of fit into the head unit

This should give me 2 pretty good lights with useful run times

LED Vf = 3 x 3.5 Volt LED’s = 10.5 Volts

Battery = 6 Volt 3000mAH = 6 volts x 3 amps = 18 Watt hours

@ 1000mAH
1.0 amp x 10.5 Vf = 10.5 watt + 20% inefficiency = 13.125 watt draw
18 watt hours / 13.125 watt draw = 1.37 hour battery life

@ 750mAH
0.75 amps x 10.5 Vf = 7.875 watt – 20% = 9.84375
18 / 9.843 = 1.8 hour battery life

@500mAH = 2.75 hour battery life

@350mAH = 3.9 hour battery life

The weight should be in the half a kilo area

I’m planning of using one of these switches

as made by the team thats put together the stunning Min-T. See here http://candlepowerforums.com/vb/show…=172053&page=5

Dom from CPF answered one of my queries with this photo

 

Here is the size of the Cutter optic and MCPCB

I’m going to mount the MCPCB onto a 42mm dia disk (made from an old trangia pan I think) so that the bezel with hold all the optics in securely. This will either work perfectly or be a bit crap. I’m going to use Artic Silve thermal epoxy. Porbably sourced from Cuttter at the same time as the Cree kit

 

Not sure at the moment how I’m going to secure the Maxflex board in the housing. Options are either to silicone it in place or to wrap it up in something and leave it to rattle around a bit

These head units seem ideal for the purpose. I brought a replacement for a damaged one a year ago for £20. They are aluminium so should conduct and disipate heat pretty well. The mounting brackets for handle bars (inc oversize) work well (I also have a plan to adapt one to make a simple helmet mount) and spared are available

 

Bit more info, this time on costings of this project if starting from scratch

Light head unit
£20 – Light Housing
£ 5 – handlebar mount
£50 – Cutter’s Cree MR 11 with (+£5 with Maxflex)
£10 + p&p – Remote switch
£10 – bits and bobs including heat paste, heat shrink and cables

£95

Battery and charger – NiMH about £30 (14.4volt 2400mAH)

 

Because the Maxflex from Taskled is a boost driver (takes the voltage up, in this case from the battery at 6 volts to the 3 leds in series 3 x 3.5 = 10.5) there are some issues with heat generation and maybe needing to disapate the heat out of it via heatsinking in some way.

 

Text from the maxflex manual: "If the power dissipation of the MaxFlex board exceeds about 1W it is recommended to affix a heatsink or copper tab to a heatsink to the exposed area."

 

George from taskled gives advice on this issue on the Candle Power Forum HERE

 

Here’s the maths

 

@ 1000mA
3 x 3.5 x 1 = 10.5 Watts
Say 90% efficiency = 1.05 Watt being disapated by the maxflex board

@ 750mA (my planned high rating)
3 x 3.5 x 0.75 = 7.875 Watts
90%= 0.7875 watts

So at 750mA no problems, at 1000mA its on it’s limits. Thats ok and fits with my plans at the moment

 

UPDATE-

 

The light is built and working, and working well. The housing worked out as planned, the switch I’m planning on using finally hasn’t arrived yet but I’ve made something up from some bits from Maplins and a bit of heat shring thats working well

 

Here’s a photo of the head unit, battery and switch

 

  

 

And here’s the switch (very pleased with this )

 

 

 

 

All mounted on the bike. I’m really into bits of recycled innertubes at the moment and they’ve proved handy for keeping it all neat

 

 

 

 

And the switch again, mounted using inner tube mount

 

 

 

 

And some helmet cam video from this evening on you tube