# Hydra-2 – 1,250 lumen Rebel light with pushbutton control



## jeffosborne (Oct 28, 2008)

This was a project that kept me busy for several months. And satisfied my desire to have a very bright portable light! Hydra-2 is a fan-cooled light I designed and built from scratch. It is very similar to the original Hydra light I built last summer:
https://www.candlepowerforums.com/threads/170249
The first Hydra has served me well, but I wanted a smaller, brighter light with pushbutton level controls instead of the toggle switches. The 2 pushbuttons on top of Hydra-2 cycle through low, medium, high, and off, with separate controls for the front light and the bottom navigation light. It weighs 1.3 pounds, and is 8.4” long. The head is all aluminum, and the tube is 1.5” schedule-40 PVC pipe with a textured spray paint finish.





I had saved 4 Rebel cool-white100-lumen LEDs from before the recall for this light, and they are driven at 800ma on high mode, for 800 total lumens from the 4 front emitters. With 450 lumens max from the navigation light, it has a total output of 1,250 lumens! It can produce that level for one hour with it’s three 18650 Li-ion batteries. Or both lights on medium for 3 hours, or both lights on low for 16.6 hours. Near to the push buttons on top of the light, the yellow indicator LED glows when the fan is on. The center red LED glows when the light has turned itself off because the battery voltage is less than 8.5 volts. And the red LED on the right glows when the light has turned itself off because the LED heat sink temperature has exceeded 200 degrees. Both red LEDs light when the light has turned itself off because the battery compartment is above 140 degrees. A quad comparator IC and thermistors accomplish most of these safety functions. When the LED heat sink reaches 120 degrees and the fan comes on, it draws air in through the 4 corners where the head and tube meet. Air is discharged through a vent on the bottom of the light. It usually takes 5 or 6 minutes on high before the fan comes on. The thin, 5 volt, 40mm fan draws only 40ma!





The 1/8” thick aluminum tail plate covers two battery charging jacks underneath. 





Here is the bottom-side view, where the navigation light resides. These 3 neutral-white LEDs output a smooth flood of light. I did not have enough of the 100 lumen per watt cool-white LEDs, so I used the brightest Rebels I had for the navigation light, 80-lumen neutral whites. 450 lumens total from these 3 LEDs at 800ma. They are covered with a 1/16” thick lexan panel. Directly under them is the exhaust port for the cooling fan. It is covered with a fine aluminum screen to help it to be splash proof, and keep debris out.





Here’s a view of the front emitters with their 20mm IMS reflectors. The white blob in the center of the reflectors is artic alumina holding a thermistor. It is wired to the comparator IC that turns on the fan. A polycarbonate sheet .1” thick covers the front emitters.

Here are some specs:
Front light (four emitters wired as 2 pairs of 2 in series)
low 100ma 80 lumens 25 hour
medium 580ma 400 lumens 4.5 hour
high 1600ma 800 lumens 1.5 hour
off to allow for navigation light only

Navigation light (three emitters wired in series)
low 50ma 45 lumens 50 hour
medium 290ma 210 lumens 9 hour
high 800ma 450 lumens 3 hour
off to allow for front light only

Beside being really bright, the long life and high efficiency of the low and medium modes were important design goals. Performing as a spot light or area light, or both, makes this light a very flexible tool. The neutral-white flood light is great for photography! Here are some highlights from the construction:




The first Hydra started with a Penium-2 CPU heat sink that was 2x2x.75” which was kind of large but needed, even with a cooling fan, because it was surrounded by plexiglass, not a great heat conductor. For Hydra-2 I chose a smaller heat sink, from an old 486 CPU, that is 1.75x1.75x.5” and enclosed it with aluminum, a very good heat conductor. Most important aspect for the 486 heat sink: the four IMS 20mm reflectors fit on top, with a little wiggle room, just a little. Quarter-inch aluminum side pieces are thick enough to allow me to drill and tap holes for #4-40 screws, which support the other pieces of the head, which are 1/8” aluminum. Let’s let the enclosure head radiate some heat. 




Here’s the front Rebel emitters just after they were glued into place with arctic alumina epoxy. The thermistor in the middle is a 50K ohm glass enclosed part, bought from DigiKey. 





Every good custom-build post needs a careful look down the reflectors at the emitters, in all their waffle-looking golden glory. I had to file away some material at the base of the reflectors to allow for the exit of the connecting wires. Well-mixed 5 minute epoxy holds these very lightweight reflectors to the heat sink. As the epoxy dried, I made small adjustments to center the emitters as best I could. 24 gauge wire was used for the short run between the emitters and the regulator mosfets.




Working with PVC pipe can be fun. It is easy to tool, and responds well to filing. The tube fits 5/8” up inside the head, and was slightly larger than the 1.75” heat sink. After filing, I used a very fine steel wool over the entire surface of the tube. That gave it a smooth finish and prepped it nicely for painting.





The paint is Rust-Oleum’s ‘hammered’ texture spray paint. It needed two coats.




The battery pack uses three 2500mah LG cells, and a protection circuit board, item# LI-PCB-14V4 from batteryjunction.com, $9.95. It is a 10.8 volt nominal pack, and includes a 168 degree thermal cut off. The manufacturer specs the battery up to 140 degrees, so 168 is right out. The round lexan panel holds a coaxial serial charging jack, and a 4-pin balance charging jack. A 5mm fuse holder is epoxyed to the panel as well. I use a 4 amp fuse. 2 spare 4 amp fuses are wrapped in plastic and tucked between the fuse holder and the serial charging jack. 





Here is the basic regulator. There are three of these mounted to the inside walls just behind the cooling fan. One regulator drives the navigation light, and two regulators drive the 4 front LEDs as two pairs. The mosfet and small signal transistor on the left are the regulator (hence the tell-tale white arctic alumina), with a 1/8 watt, 10 ohm resistor as the ‘sense’ component; it sets the regulator to 50ma. When a level button is pushed, a counter IC pin goes high that turns on one of the two mosfets on the right, which adds a 2.4 ohm or .68 ohm 2-watt resistor to the sense component. This raises the output current to 290 or 800ma. These Fairchild mosfets have a very low on resistance, and are 85 cents each at Future Electronics: FQP50N06.





With the circuits all removed, it looks like a lot of wire, but it is manageable. The PVC tube is roomy, and really is a good feel in the hand. The textured paint offers some grip, as well.





Here is a close up of the controller PCB – the two IC’s on the right are the 4017 counters that take the pushbutton presses and sequentially raises output pins high, up to 10 steps. I needed only 4 steps (off, low, med, and high) so I attached the fifth output pin to the RESET pin and viola – a 4-step sequencer. The counter’s output pins are connected directly to mosfet gates for the brightness level controls. The IC on the left is an LM239 quad comparator. Next to it is a LM336 2.5 volt precision reference diode, used as a stable voltage reference for the comparator. A small 5 volt regulator drives the cooling fan, when it comes on. The one blue 20K potentiometer adjusts for the 8.5 volt detection, which powers down the light when the battery drops too low. The battery pack’s protection PCB from batterjunction.com would turn off the circuit at 7.5 volts, too low for best practices. This PCB resides in the tube, underneath the on-off rocker switch.





Forum member glockboy built a light a while back that inspired my efforts here, his 10-Cree Makita light. My hat is off to him and the many other great innovators here on the forum!
Hey, I will have some beam shot photos for you ASAP…

Jeff O.


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## bluecrow76 (Oct 28, 2008)

A truly unique light! Well done! :twothumbs


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## cryhavok (Oct 29, 2008)

Awesome! :thumbsup:


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## toby_pra (Oct 29, 2008)

Looks very futuristic... :thumbsup: Crazy! :naughty:


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## jeffosborne (Oct 29, 2008)

*Re: Hydra-2 – beam photos added...*

As promised, here are beam shots for you. This first one shows the color difference in the front cool-white Rebels and the neutral-white variety on the lower navigation light.




On the left I have a 3 D-cell stock Mag-lite with fresh batteries, set to a narrow focus, and the Hydra-2 on the right on low level, appx. 80 lumens. They are 6' away from the wall.




And with the Hydra-2 on medium, about 400 lumens.




Here the Hydra-2 is on high mode, 800 lumens or so.




The Mag-light will get a modification/upgrade one of these days. 

Jeff O.


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## Kiessling (Oct 29, 2008)

*Re: Hydra-2 – beam photos added...*

Very unique concept and style and great write-up !!
:thumbsup:
bernie


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## TigerhawkT3 (Oct 30, 2008)

Can you say awesome?

Because I sure can.


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## traumerei (Oct 30, 2008)

That navigation light is something I haven't seen before. Was that your idea? I'm surprised it isn't more common considering many (maybe most?) use their lights for walking around.


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## ICUDoc (Oct 30, 2008)

Thanks Jeff O. An interesting write-up. I particularly like the way your machining has evolved from Hydra I, and the navigation lights seem so sensible!


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## Firecop (Oct 30, 2008)

This build looks fantastic - well done!


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## Thujone (Oct 30, 2008)

:twothumbs:candle:


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## jeffosborne (Oct 30, 2008)

Thanks for the kudos, everyone! I am humbled.

As for the navigation light, traumerei, it was not my idea.
I saw a modified LED flashlight here on the forum a year and a half ago that featured a single Cree emitter on the side of the head, as a navigation flood light. I searched but could not find the original post. It might have been a Mag mod. Many superb ideas are floated here at this forum. One just has to keep reading to get tons of info, ideas, and inspiration.

Tat tvam asi!

Jeff O.


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## Hodsta (Oct 30, 2008)

very impressed jeff - the light is interesting indeed and the write up is great:thumbsup:


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## Cheapskate (Nov 4, 2008)

Excellent stuff! It is nice to see someone build something so functional without needing a machine shop full of CNC equipment to do it. :thumbsup:


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## degarb (Dec 27, 2008)

*Re: Hydra-2 – 1,250 lumen Rebel light with pushbutton control*

1. I like rebels (color rendering / price). 2. I like 4 2x2 parallel (efficiency). 3. The 7.2 volt level works well with headlamp and belt mounted battery (think 6 volt agm with AA NiMh in series, or four 18650s)

I was wondering where did you get the reflectors?

What I don't like is drive level. Missing 200, 300, and 400 milliamp levels. I personally don't like driving leds past 400 milliamp level for several reasons (heat, lumen droop, runtime).

Could you make me one in a head lamp version, with missing drive levels?


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## jeffosborne (Jan 1, 2009)

Hi degarb, thanks for the shout.

1. I agree, rebels are the bomb for tint and smooth dispersion
2. efficiency is always good...
3. for a headlamp, I've not experienced the whole belt-pack battery setup, the few I have are coin-cell or 3-AAA (arghhh...)

I bought my IMS reflectors from Future Electronics, part# SO20XA, $1.53 each when I got them in Aug. 2008.

At the lower drive levels you mention, a quad emitter headlamp might get by without the fan cooling. But it still might be a bit bulky.

I could make a headlamp for you, but that would rob you of the opportunity to further your own design skills. Besides, only YOU really know just what the final design should be. I am flattered that you have asked, though. And I'd be happy to consult on your project! 




Happy 2009 everyone! 

Jeff O.


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## Kiessling (Jan 1, 2009)

jeffosborne said:


> As for the navigation light, traumerei, it was not my idea.
> I saw a modified LED flashlight here on the forum a year and a half ago that featured a single Cree emitter on the side of the head, as a navigation flood light. I searched but could not find the original post. It might have been a Mag mod. Many superb ideas are floated here at this forum. One just has to keep reading to get tons of info, ideas, and inspiration.
> 
> Jeff O.




This one?







LED Lenser had also some lights that used blue or red 5mm LEDs as navigation lights. They were not very succesful though 

bernie


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## jeffosborne (Jan 2, 2009)

Bing! Bernie, I believe that light is what I had seen. Did you modify that light, and did you publish it here some time ago? 

As well, how is the navigation light switched? With the forward light or separately?

Thanks for sharing, and happy new year! 
Hooray for navigation lights!

Jeff O.


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## Oznog (Jan 2, 2009)

Have you considered trying home anodizing? Not that difficult, actually, and the finish is actually better at radiating away heat than bare unanodized aluminum, and much better than painted aluminum.


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## gav6280 (Jan 2, 2009)

Top effort for producing something unique and different. But personally i don't think i like the look of it, but that's just my own personal opinoin...

You should definatley looking into anodizing.,.


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## degarb (Jan 3, 2009)

*Re: Hydra-2 – 1,250 lumen Rebel light with pushbutton control*



gav6280 said:


> Top effort for producing something unique and different. But personally i don't think i like the look of it, but that's just my own personal opinoin...
> 
> You should definitely looking into anodizing.,.



I must be missing something. I thought they just help you see in the dark, and extreme detail from afar in medium to low light. But apparently, they have a far different of which use that I was unaware. This should make us rethink the whole preferred battery format.


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## jeffosborne (Jan 4, 2009)

gav6280 said:


> Top effort for producing something unique and different. But personally i don't think i like the look of it, but that's just my own personal opinoin...
> 
> You should definatley looking into anodizing.,.


 
My aluminum work does suffer from dings and blemishes that would not be a problem with an anodized finish. And of course a black anodize would radiate heat all the better. Thanks for the nudge, Oznog and gav6280, I hear ya. 

As for the look of the Hydra-2, I do recognize its resemblance to the Frankenstin monster, all blocky and bolt-head ridden. But the 'built like a tank' factor weighs in as an appealing aspect, and it can seem almost elegant in light of that. And performance is great - I use it all the time now.

The 486 heatsink and fan were the primary elements. Perhaps if I had started with a round heatsink....





Cheers,
Jeff


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## mpf (Jan 17, 2009)

Great torch. I like the area leds and especially the cooling fan. 5V at 40mA is very usable in high powered torches.

matthew


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## jar3ds (Jul 1, 2009)

very sweet!


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## supasizefries (Jul 2, 2009)

Damn very unique lights you've built there. I like it! :twothumbs


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## LightSward (Oct 3, 2009)

:thumbsup: I like this light. Well constructed. Can you get some good outdoor beam shots or hillside illumination shots? That thing shines!


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## jeffosborne (Oct 3, 2009)

Thanks for the kind assessment of my Hydra-2 light, LightSward! In answer to your request for additional beam shots, I went to my back yard this evening with camera and tripod and made the photos below. The camera settings were ISO 100, 3.2 second exposure, at 5.6 f-stop. We are 45 feet from the back of my house, which is down a 6 or 7 foot slope in the lawn. In this first pic, we see the nearly ful moon peeking through some leaves up above, and three of my outdoor dusk-to-dawn LED lights. The two on the deck are neutral white rebels at 400ma, and the one to the far right at the top is one of two over my drive way, and they are cool white rebel LEDs.




So I switched off the LED lights on the deck area, and made this control shot - a few indoor lights and the one driveway LED light are still visible.




Now we see the Hydra-2 on low power, about 80 lumens. Clouds begin to obscure the moon.




Next the Hydra-2 is on medium power, perhaps 400 lumens or so. Now we are beginning to see the spill from the light on the grass on the foreground, and on the few leaves at the top of the photo.




And now with the light on high power, about 800 lumens. Here the foregound is brighter on account of the spill. You can see that the camera angle does not capture all of the spill's width. Inside the house, the family is wondering what the heck I am doing...




One more shot, where I have moved forward with the light about 15 feet. Here you can see the navigation light too, also on high mode. The nav light is made with the warmest neutral white rebel LED's offered - the RM bin. Notice how warm the grass looks.





I will strive to go to a more spacious venue soon to shoot more outdoor photographs. It was a bit of fun shooting these!
Jeff O.


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## LightSward (Oct 4, 2009)

:thumbsup: Incredibly bright and small size too!


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## Illum (Nov 2, 2014)

Sorry to  an old thread, [it was a fantastic read btw ] but could you elaborate on the 4017 mode sequencer a bit? Namely what does it do to increase or decrease output? Does the 4017 output turn on or off a transistor that parallels another sense resistor beside the one set at low to create a higher output? 
I'm hoping to adapt this idea for table top lamps. Using a pushbutton as the I/O without leaving the realm of analog electronics


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