# Electronics, Lighting, & Gadgets - Resistors in the 2-mode P7 torches

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shuffles
03-13-09, 09:02 AM
Howdy all,

I want to make my 5-mode MTE (DX 12060) a 2 mode by removing the driver and adding resistors to the tail switch. I'd like to be able to run at full power and at 75%. Currently, the medium mode is reported to be about 30%.

There's been some discussion in the past about what resistor values to use, and I'm currently thinking I would need about a 1 Ohm resistor to bring it to 75%.

It's also been suggested to use a 2 watt resistor for this application. A 2 watt resistor is huge, and I cannot believe that it would actually fit in the tail cap of this flashlight. :wtf:

What value and capacity resistors are included in the 2-mode lights from MTE, Aurora, Trustfire, etc?

Let's discuss.

Thanks!

Unknown Cyclist
03-13-09, 09:35 AM
I have the 2 x 18650 Aurora P7 (and very good it is too).

Here's some of the measurements I've taken:

On high:
Runtime = 2 hrs 16 mins (continuous)
Current draw from battery = 1.16A (measured) Voltage unmeasured
Voltage at P7 = 3.34V (measured)
Current at P7 = 1.42A (calculated)
Estimated Watts @ LED 4.7W
Lumens = 400 ?

On low:
Runtime = 5 hrs 43 mins (continuous)
Current draw from battery = 0.6A (measured) Voltage unmeasured
Voltage at P7 = 2.99V (measured)
Current at P7 = 480mA (calculated)
Estimated Watts @ LED 1.4W
Lumens = 140 (estimated)

Resistor in tailcap = 7.5 ohms (measured)

Battery recharge time 7 hrs 50 mins

Weight inc. batteries 374 g (13.2 oz)

Hope this is of some help to you, see my signature for the review thread or ask if there's anything else I can let you know.

shuffles
03-13-09, 09:43 AM
Thanks UC. 7.5 or 8 Ohms is about what I figured for these stock lights. What current value is it? Is it a standard wire wound resistor?

Unknown Cyclist
03-13-09, 10:03 AM
I'm not an expert, however, it looks the same as some metal film and carbon resistors I have.

http://images.maplin.co.uk/full/dk2.jpg

When you say standard wire wound, do you mean the white ceramic block type ?

What are you hoping to achieve ?

shuffles
03-13-09, 11:32 AM
No, I mean just like you pictured here, whatever that kind is. From my googling, it looks like the body of a 2 watt resistor would be about 15mm long (length of 0.688 inch and diameter of 0.318 inch), and a 1 watt would be about 11mm long. Which one does yours look like?

So, how big is your resistor? :)

Oh, and I'm hoping to achieve the same functionality that you have in your 2-mode flashlight. The 5-modes don't have any resistors, they just have the driver which I intend to remove. So, they resistor would be connected to the clicky and would be used to dim the circuit.

Unknown Cyclist
03-13-09, 11:41 AM
No, I mean just like you pictured here, whatever that kind is. From my googling, it looks like the body of a 2 watt resistor would be about 15mm long (length of 0.688 inch and diameter of 0.318 inch), and a 1 watt would be about 11mm long. Which one does yours look like?

I'll check and get back to you.

Is your torch 1 x 18650 or 2 x 18650 ?

Are you going to direct drive the LED ?

There's little reason to consider that a similar size resistor will get the same results, as my 2 x 18650 torch is regulated, so unless you have the save regulator and same voltage in, you won't get the same results.

shuffles
03-13-09, 11:42 AM
I have a 1x18650. (http://www.dealextreme.com/details.dx/sku.12060)

Unknown Cyclist
03-13-09, 11:44 AM
Are you going to use a regulator ?

shuffles
03-13-09, 11:47 AM
Not planning to.

Unknown Cyclist
03-13-09, 11:56 AM
The resistor in my torch is doing a subtly different job then.

You currently have a 5 mode driver which is operated by a momentary switch.

As well as removing the driver you'll need a different switch.

Calculating the correct value for the resistor would be easy if the LED had a linear response, which it doesn't, trial and error might be the easiest solution.

Rather than destroying the torch you have just buy a torch body kit from DX for \$11.50 and play with that.

Torch Body Kit (http://www.dealextreme.com/details.dx/sku.15946)

EDIT: Scratch that...it's not P7......

Or just buy a torch that suits you. :thumb: