Would it be possible to power an external led light from mobius' internal battery

[TheDashDepot]

Could I connect for example 3 LEDS in series (1.5V 50mah each) directly to the battery? Or would the LEDs' draw be potentially too much for the camera to function properly? Is there a high risk of frying the board somehow?

 

[Rajagra]

IMO It would be better to buy a decent torch (and possibly even power the Mobius from it?) if you are aiming to create a video light.
Torches are amazing these days. And cheap, and small.
I have ThruNite Ti3 and Olight i3E torches. They are insanely bright and barely bigger than the AAA batteries they run off.
No adjustable focus though, so you might need to improvise a diffuser.

 

[SawMaster]

It could be done well but not quite as easily as you think. Or it could be done easily but with poor light performance. LED's function best with a driver which keeps the current flowing at a level the LED performs well at. You can go direct-drive but as the battery weakens, so does the light and you have to under-drive the LED's so a full battery doesn't burn them out; given the battery capacity it would dim rapidly. If you want to try this I'd look for a single emitter with a vf at or above 3.5V and a boost driver to maintain and regulate the needed current; stronger light longer but a shorter runtime overall. But chances are that drawing more current from the cam battery will either make the camera malfunction (lack of the minimum power it needs) or shorten the runtime down to a very few minutes. Either way the last file will probably not close properly for a lack of the power needed to do that.

Have a look at the Nitecore "Tube"- high lumens in a flat rechargeable form-factor that would complement the Mobius without compromising its performance. Their new "Tip" may also do well. You'd end up with a thicker package but no bigger otherwise that would still be very compact and reliable without the need for any 'engineering' work on Mobius.

Phil

 

[TheDashDepot]

Thanks for the info. I should have mentioned that this is for infrared leds. I modded the mobius by removing the IR filter from the lens to achieve night vision. I'm trying to keep it as minimal as possible, build in would be great. I'll see how connecting to a separate battery directly works out. If that'll have poor results, I'll look for a flashlight with IR leds or maybe I can mod a normal one.

 

[Rajagra]

The old way to run LEDs was to just to put a resistor in series with them. The resistor value is chosen to feed the correct current for the LED given the source voltage minus the voltage drop across the LED. It was a perfectly good method when LEDs were low power devices.

You can increase efficiency by using multiple LEDs in series with the resistor. This makes the voltage across the resistor lower, hence less wasted energy for the same current. The problem though is that if the source voltage drops, it affects the setup much more.

For example using a 3.7V battery, a resistor and an LED with 1.8V forward voltage, the voltage across the resistor would be 3.7-1.8=1.9V
If the battery voltage drops by 0.1V, the volts across the resistor drops to 1.8V. The current, and brightness would drop by about 5%.

But if you used 2 LEDs in series instead of one, the voltage across the resistor would start at 3.7-1.8-1.8=0.1v
You could choose the resistor to give the correct current, you'd have twice the brightness (2 LEDs), but 19 times less wasted energy via the resistor.
BUT it the battery drops by that same 0.1V, there would be no voltage across the resistor, no current, no light.
Instead of the brightness dropping by 5% you'd get nothing - 100% less light!

 

[SawMaster]

IIRC, the Nitecore "Tube" can be had with an IR emitter I'm seeing parasitic drain problems being noted with the "Tip" though, best avoid that one for now. There's no point in 'rolling your own' unless you simply want to. You can usually buy better than what you can put together for the same money or less. Drivers can be had so cheaply now there's no real point in using direct resistance for current control, and as I already pointed out, going without a driver means the light begins dimming from the moment you turn it on. Since you won't be able to see that IR light you'd be better off with a driver which ensures you of a steady output so that the cam settings will remain optimal during use. Just the last few years has seen LED flashlight technology mature with efficiencies undreamed of in the past in all parts: cells, drivers, and emitters. The cheap lights and cells are a minefield of fakes but nearly top-level lights can be had for so little more there's no point in buying the cheap stuff and modding it or making your own.

If you decide to buy a pre-made light, PM me and I can probably get you a substantial discount from one of the Chinese mega-stores. If you want to do a build I can help you there too

Phil

 

[Dashmellow]

I'll bet the Mecarmy SGN3 XP-G2 would make a great companion illuminator for the Mobius. It puts out white (160 lumens), red or UV light and could probably also be fitted with an IR filter.
The similar form factor and similar size would make for a nice little "system" if held together with Dual-Lock tape.

USB rechargeable multifunction flashlight
Quick charge in 90 minutes
Standard micro-usb port
Built-in 280mAh lithium polymer battery
Three selectable LED outputs (White/UV/Red)

Dimensions:
Length: 59mm / 2.32in
Width: 23mm / 0.9in
Height: 10mm / 0.39
Weight: 38g / 1.34oz (excluding battery)
Charging time: 1.5 hours (charging current 100mA)