simple PWM generator?

[B30wuLF]

i am bilding a triple P7 6D mag at the moment using wichtels kit and driver.

i ll be using the light mostly for camping... and i need a "low" mode (ca. 20%) in this light. i dont want to put in a ultra mega multi mode dimmer just a small switch for 20=>100% aditionally to the normal on off switch.

any sugestions on a PWM generator circuit to generate a signal for the driver?
i just need the scematics. i can build it myself?

 

[Magic Matt]

PWM is just basically a timed on/off pulse. You can build one with a 555 timer. http://www.dprg.org/tutorials/2005-11a/index.html

The problem I have is that I can't produce surface-mount circuit boards. The issue isn't so much building the circiut, as building it small enough to fit in the light with everything else. You might be able to make that circuit without a board soldering direct to pins on compoenets then sealing it in epoxy. You will need to check frequency and voltage requirements of the board you're using and adjust the circuit accordingly.

 

[B30wuLF]

thx thats what is was looking for.

i have lots of space in the mag to build it on a normal through hole board and cover it in epoxy, even with the driver. i ll just put in a small switch that connetcs the pwm output to the driver and a mini poti to tune the low level.

 

[TorchBoy]

Another way to do it would be to buy an inexpensive dual layer driver, where one layer is the driver and the second layer is the mode driver, and pull them apart to use the PWM controller half. The driver itself will probably find a use somewhere else.

 

[B30wuLF]

also an option.
do you know a cheap DX/KD driver that has just a 20% or so mode i can use ?

fyi: i get the components for free, so it has to be really cheap.

 

[TorchBoy]

How about one of these? http://www.videofoundry.co.nz/ianma...max=5&stock=instock&type=buck&modes=multimode

 

[B30wuLF]

not bad i think i have one of those in my collection.

i build a worklight with the 3V~8.4V 5W Cree 3-Mode Memory Circuit Board for Flashlights (16.7mm*6.1mm) driver and the moode memory with the strobe drives me nuts!!! to get fom low to high you always have to go to strobe mode first.

my idea to build a secons switch in to the mag seems to be rather complicated if i do it at least splash proof.

the ideal solution would be one of those 3 buck dx/kd divers with just low and high mode (in that order) with a separate pwm board. no memory. no sos strobe poop nobody really needs. sady most of them are (if they only have 2 mode) in the reverse order high => low.
if i use a 3x800 lm light for camping i dont want to blind everybody first thing i switch it on.

 

[Magic Matt]

I think the PIC chips you get that the drivers are based on aren't available without memory etc. so they take the attitude that if the capability is there, why not provide it.

Possibly you could reprogram the chip on the driver to just have the modes you want, but you'd need a programmer and a desire to get down and dirty with the code. Personally I love that side of things, I just don't have a clue on the electronics that go around the chip. LOL!

I have plans for driver, but I'm going stir-crazy waiting for the bits to arrive. I'm attempting to program a 'very soft on' feature with a soft sliding up/down in brightness rather jumping to the different levels. I'm going to make use of the hipCC from TaskLED for mine, and build the control system. I will be sharing when I get it working so others can take it further in terms of miniturisation, but it probably wont happen quickly.