[chbot] Chchrobotics Digest, Vol 141, Issue 4

Helmut Walle helmut.walle at gmail.com
Thu Jun 27 13:05:38 BST 2019

Many if not all do use PWM - you can see it when you are out in the 
rain: the rain drops look like " - - - - -" for the 50% brightness 
setting, and a continuous line for full on. It may just be possible that 
those that go CW for full on do not emit a lot of RF on the "high beam" 
setting... However, if they have a buck converter, then that would still 
emit some RF. But I for one wouldn't bother with a converter at all, and 
instead just PWM-feed DC straight from the battery through the LED. It's 
cheap and easy, and unless optimisation for efficiency, also including 
exploiting the battery's capacity as best possible, are important, PWM 
works pretty well. Most of all it's cheap, and that surely must be a key 
requirement for most of these lights.

There are some more interesting (and higher-priced) lights on the 
market. For example, LED Lenser are proudly marketing some of their 
lights as being dual-mode: they can do brightness control like pretty 
much all the other brands, but you can switch them to an uncontrolled 
mode where they gradually fade as the battery discharges - now I am not 
sure whether that mode is PWM-free, though.

Kind regards,


On 27/06/2019 11:40 PM, ceo at andygardner.com wrote:

> Many LED headsets have selectable intensity. Push once for full on, 
> again for slightly dimmed, etc.
> $10 says the ones they have are using PWM for intensity adjustments.
> [...]
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