Comparing lights
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footleg
New member
potholer said:
For example, I recently discovered that LED lights which use PWM* to provide their lower power settings can generate interference patterns on footage recorded on my HD video camera. The result is horizontal bands which are darker than the rest of the image moving upwards across the frame. So for my needs I require something that runs the LED on full power constantly. In terms of lumens/? you will find it hard to beat the MagicShine bike lamps http://www.dealextreme.com/details.dx/sku.25149 which really do run the SSC P7 at full power and cost around ?50 (subject to exchange rate fluctuations). The P7 LED torches mentioned above do not run the LED at full power, as the power in the battery cannot last the run times quoted for them. The MagicShine light lasts 3 hours off 4 Lithium cells. Handy for video and photography, but only suitable for short trips if used as a caving light. Probably a good thing as they also rely on airflow over the lamp for cooling, so you have to cave fast with them to stop them overheating!
* PWM = pulse width modulation. Basically the light is turned on and off repeatedly by the control circuit so that it is only on part of the time, but too rapidly for the human eye to detect. By being off part of the time the power consumption is reduced, extending battery life but giving an apparently lower brightness level.
Burt
New member
Footleg - Very interesting. I was recently cleaning the inside of my central heating boiler (oil fired) after a "sooty cloud in the kitchen" incident and using a Tikka to light the firebox. As the light got close to the soot deposits on the metal (within 3") the soot buzzed quite loudly. Any idea why?
footleg said:
Lights using PWM cause a strobing effect in my peripheral vision (and a couple of others I have spoken to have noticed this effect too). These include scurions, and is the main reason I went for a Stenlight.
It's very noticeable with the new generation of LED Car tail lights too, if I end up stuck behind one I have to slow up and let it get well away from me. Good job I'm not epileptic, though it's very annoying.
Flicker does depends on what the frequency is.
I think I'm running a PWM of around 300Hz for low power modes, and that doesn't seem to cause flicker.
Trying to get regulation at really low power can be pretty hard without using PWM.
Currently, I'm playing with sticking an extra-low-power 'moon mode' into a light, and the currents involved are tiny (more a case of how many weeks of runtime than how many hours).
Running that power level at constant current wouldn't be easy without adding circuit complexity. With PWM, it's a doddle.
I think I'm running a PWM of around 300Hz for low power modes, and that doesn't seem to cause flicker.
Trying to get regulation at really low power can be pretty hard without using PWM.
Currently, I'm playing with sticking an extra-low-power 'moon mode' into a light, and the currents involved are tiny (more a case of how many weeks of runtime than how many hours).
Running that power level at constant current wouldn't be easy without adding circuit complexity. With PWM, it's a doddle.
mountaingoat
New member
The Scurions use it only for the lowest setting. The upper 3 settings don't.Maggot said:
I thought Tikkas used a pretty simple unregulated PWM with just transistors/resistors, not anything fancy using inductors.footleg said:The evidence would appear to point to the circuitry in the light causing the buzzing, but I have no idea why or how! Maybe the light causes magnetic interference and the soot particles were charged due to static electricity?
As a result, magnetic fields would seem likely to be tiny at even short distances.
caving_fox
Active member
It's one of the minor things I quite like about the Scurion - if you're waiting around at a pitch you get to enjoy strobed mist particles dancing in the beam. It's far nicer than just watching a cloud. YMMV.
The Bisun
http://www.bisun.co.uk/
http://www.bisun.co.uk/
There's no Bisun mining lamp insert in the latest set of shots, and shots from the previous test last year with a P31 would be limited use for a purchasing decision, since I'm migrating across to newer (brighter) LEDS, and I'm also currently reconfiguring the drive electronics to add a couple of things I wanted in there, giving options for more light and for increased battery economy.
The only light I had in the recent comparisons was my nice new Duo spot conversion.
The only light I had in the recent comparisons was my nice new Duo spot conversion.
menacer
Active member
Potholers Bisun was included in the first round of Lights, and did very well in terms of costs and light output value for money IIRC.
It will take time for Wookey to put the next batch together, (maybe for hidden earth as a guess)
In the meantime there is an online comparison of the lights tested on the darkplaces website, I'll try find the actual link.
http://www.darkplaces.co.uk/lampbeamcomparison/
It will take time for Wookey to put the next batch together, (maybe for hidden earth as a guess)
In the meantime there is an online comparison of the lights tested on the darkplaces website, I'll try find the actual link.
http://www.darkplaces.co.uk/lampbeamcomparison/
big-palooka
Member
Potholer - when is the retro fit super led for the petzl duo likely to be available for us to purchase
:bow: :bow:
Paul C
:bow: :bow:
Paul C
