Homemade lightweight dual P7 headlamp

Jagge

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Jun 17, 2008
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Happenned before:
https://www.candlepowerforums.com/threads/201836
https://www.candlepowerforums.com/threads/212401

Update. 2009 season version:

dualp7_1.jpeg


dualp7_2.jpeg


About same design as before, but now with two P7 LEDs in series. Two modes, 1.75A and 0.35A. Modes should give about 1100 and 260 lumens and burn with the belt pack shown 1:25 and 7 hours. Enough for my runs, low mode is fine for slow path jogging, high for my typical ~1 h races.

Weight without battery is 114 g and total weight with shown nimh battery pack 337g. Li-ion might save ~70g.

Light heads are now monteed with rubber bands. I may keep it that way and just add some double sided tape to prevent sliding. It is nice to be able to make beam spot changes by changing one of the heads direction. It's also good to have two heads, you can modify beam by using different lenses on the heads.
 
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ahorton

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Jul 22, 2008
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Do you find that it bounces around when you run?

I've found that anything more than 30mm from the head starts to bounce around, even if it is only 50 grams.
 

Jagge

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I haven't tried it in action yet, but it didn't feel like bouncing when I was jogging indoors with it. I think it should not be a big problem or at least there suold be workarounds. Forehead plastic part is quite high (wide), if it "rolls" up and down on my forehead I can put something soft at top/bottom edges to make better fit to my head. Top srap can be added too. The bouncing part - lamp head - weights about 50-60g, rest is headband and wire. It's pretty close to the head too, but I can't say how far the centre of gravity is. Camera's perspective makes it look huge in the first image, the display trophy isn't even nearly as as big as my head either.

It this will not do, I'll try some more robust headbands I have. I'll let you know how "Walle" behaves.
 
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Jagge

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It did not bounce as it is, or at least bounced so little it didn't bother me. It's still not known how well it stays at it's place on foreahead during race conditions & sweat.

I did some measurements. Vf at high was 6.35V. I use AMC7135 driver, slave P7 is between driver and battery pack. After losses in driver and wires to belt pack I need about 6.75V battery voltage to stay on regulation. Looks like it fits well for 6 x nimh cell pack and AMC7135. Average driver efficiency should be about 92-94% (?) and at the end of the battery capacity it drops out from regulation and slowly dims as the driver direct drives. I should work well with 2 x li-ion cell pack too.

The battery pack in the photo is 7 x nimh. During my run the slave lamp head (the one without driver) ran cool, but the master one with the driver was quite hot. Not too hot to touch but hot anyway. 7 cell pack gives too much voltage for the driver. I'll take one cell off, then master head should run cool as well, output and runtimes should be the same but total weight will come down to about 310g.
 
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degarb

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Oct 27, 2007
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Location
Akron, Ohio
Interested to see your final thoughts and beam shots. Parts list too. How is color rendering/tint?

If used for work, a 6 volt/4.5 AH AGM with 2 AA on belt would be a cheap

250 cycle choice.

Probably, at sustainable 400 millamps, this would produce impressive lumens.
 

Jagge

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Jun 17, 2008
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I haven't used it too much yet, there is no darkness before 11pm these days here. But I took some white wall beamshots.

left Lupine Wilma (830 lumen).
image1, image2

Spots are quite similar but the spot is all Wilma has. Dual P7 has other qualities too
Image3

Dual P7's tint is a bit warmer. Actually the other P7 is warmer as you can see. Kaidomain bin...

left Kaidomain 100 lumen cree R2 flashlight:
Image4
 

degarb

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Akron, Ohio
You rock, man!

Got beam shot on 260 lumen mode (how many milliamp draw from your 7.2 volt source?) v. a 100 lumen light? Running it at high mode would create too much heat, I would think.

Too lazy to lookup your parts too. What was the total cost?

Also, for me some type of lens is essential.
 

Jagge

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Jun 17, 2008
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I use kaidomain 8 x AMC7135 regularor, originally 2.8A. I removed 3 chips (and one diode) and got 1.75 A. That's high mode. One removed chip and diode I used for low mode. I soldered with tiny wires to switch similar way I did in previous lamps and dropped some epoxy on it.

This regulator is designed to drive only one led with about 3.6V, so slave led has to be between regulator and battery. This also means I had to put regulators and switch to lamp head.

So high mode is 1.75 A and low is 350 mA and because this is linear regulator that's also what it draws from the batery. I have no idea what R2 flashlight does. But likely it is not as bright as was claimed, as usual. I have no photos of the low mode, but P7 @ 350 mA x 2 is decent amount light for tying shoe laces... I may take some beam shots one day.

I like these regulators, you can get what output you like in 350ma steps by removing chips / connecting drivers parallel.

It gets hot on table, but running airflow cools it down nicely. 1.75 A is not much for P7 after all, it's only about 440 mA per die. Running airflow is keeps it easily cool enough. Regulator also limits current if it gets hot ad it is glued with thermal epoxy right next to the "master" led, so I can't see why I should worry about it.

Parts, 2.8 a AMC diver, switch, 2 x DSXOJ P7, 28 mm diameter glass lenses, reflector is taken from a DX R2 dropins, same as before I hade these two left from the previous project so I used these, some epoxy, connectors etc. I think cost was slightly less than $100 without battery pack.
 

JHJHJH

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Sep 10, 2008
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Great design! I made a replica of Wally-E lamp using MCE leds (parallel connection), ACM 1400 mA driver and a bit more flexible modular design. Reflectors are probably those:

https://www.dealextreme.com/details.dx/sku.3257


Modular desing allows me to drive leds in series with 6 AA batteries in pocket or backbag for max output.

For jogging I can use leds in paraller connection with same driver with 3 AA batteries... I just need to change one cable and battery holder to chance lamp from 500 lumen to 300 lumen version.

Only hazard is that ACM drivers are not ment to be used to drive 2 leds in series connection. It should not be possible but seems to work nicely. After testing that once accidentally I have continued to do so. Jagge's method of using driver in bethween leds would be better, but it makes cabeling more diffiicult. In worst case I will loose one driver costing 2 euros, but having still 9 left that does not bother me. I have tought that if it lasts for one hour there is change that it will last forever...

Led in use are not the most effective at the moment, but I prefer warmer tints in orienting and forest running use (not to mention that i had free extra sample leds with yellow tint to try something funny). Modular desing allows me to switch the leds in a few moments so I will continue seek the best combination. Yellow tint is better for fog and snowing and also for reading map, so might be that yellow tint will stay...
 
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