Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Electronics, Lighting, & Gadgets HRM, GPS, MP3, HID. Whether it's got an acronym or not, here's where you'll find discussions on all sorts of tools, toys and gadgets.

Reply
 
Thread Tools Search this Thread
Old 03-13-09, 09:02 AM   #1
shuffles
Embracing my inner Fred
Thread Starter
 
shuffles's Avatar
 
Join Date: Jun 2007
Location: Pretty far west of Alpe d'Huez
Bikes: Early 90s Specialized Epic Pro carbon/DA
Posts: 360
Question Resistors in the 2-mode P7 torches

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.

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

Let's discuss.

Thanks!
shuffles is offline   Reply With Quote
Old 03-13-09, 09:35 AM   #2
Unknown Cyclist
Senior Member
 
Join Date: Jul 2008
Location: UK
Bikes:
Posts: 1,757
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.
Unknown Cyclist is offline   Reply With Quote
Old 03-13-09, 09:43 AM   #3
shuffles
Embracing my inner Fred
Thread Starter
 
shuffles's Avatar
 
Join Date: Jun 2007
Location: Pretty far west of Alpe d'Huez
Bikes: Early 90s Specialized Epic Pro carbon/DA
Posts: 360
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?
shuffles is offline   Reply With Quote
Old 03-13-09, 10:03 AM   #4
Unknown Cyclist
Senior Member
 
Join Date: Jul 2008
Location: UK
Bikes:
Posts: 1,757
I'm not an expert, however, it looks the same as some metal film and carbon resistors I have.



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

What are you hoping to achieve ?
Unknown Cyclist is offline   Reply With Quote
Old 03-13-09, 11:32 AM   #5
shuffles
Embracing my inner Fred
Thread Starter
 
shuffles's Avatar
 
Join Date: Jun 2007
Location: Pretty far west of Alpe d'Huez
Bikes: Early 90s Specialized Epic Pro carbon/DA
Posts: 360
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.

Last edited by shuffles; 03-13-09 at 11:41 AM.
shuffles is offline   Reply With Quote
Old 03-13-09, 11:41 AM   #6
Unknown Cyclist
Senior Member
 
Join Date: Jul 2008
Location: UK
Bikes:
Posts: 1,757
Quote:
Originally Posted by shuffles View Post
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.
Unknown Cyclist is offline   Reply With Quote
Old 03-13-09, 11:42 AM   #7
shuffles
Embracing my inner Fred
Thread Starter
 
shuffles's Avatar
 
Join Date: Jun 2007
Location: Pretty far west of Alpe d'Huez
Bikes: Early 90s Specialized Epic Pro carbon/DA
Posts: 360
I have a 1x18650.
shuffles is offline   Reply With Quote
Old 03-13-09, 11:44 AM   #8
Unknown Cyclist
Senior Member
 
Join Date: Jul 2008
Location: UK
Bikes:
Posts: 1,757
Are you going to use a regulator ?
Unknown Cyclist is offline   Reply With Quote
Old 03-13-09, 11:47 AM   #9
shuffles
Embracing my inner Fred
Thread Starter
 
shuffles's Avatar
 
Join Date: Jun 2007
Location: Pretty far west of Alpe d'Huez
Bikes: Early 90s Specialized Epic Pro carbon/DA
Posts: 360
Not planning to.
shuffles is offline   Reply With Quote
Old 03-13-09, 11:56 AM   #10
Unknown Cyclist
Senior Member
 
Join Date: Jul 2008
Location: UK
Bikes:
Posts: 1,757
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

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

Or just buy a torch that suits you.

Last edited by Unknown Cyclist; 03-13-09 at 12:01 PM.
Unknown Cyclist is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 07:03 PM.