[sdiy] SMD LED intensity and lenses

[Ben Bradley]

Speaking of "analog" PWM:

On Thu, May 25, 2017 at 5:44 PM,  <rsdio at audiobanshee.com> wrote:

> PWM can be accomplished with an entirely analog circuit.

I haven't looked closely, but I suspect it could be done using only a
555 timer chip (and passives) for a single LED. For many LEDs it could
be done with a single 555 for the oscillator and a comparator for each
LED.

To isolate any generated noise, put an electrolytic cap (maybe 10uF to
100uF and parallel a smaller ceramic cap) across the power and ground
of the LED oscillator/drive circuitry (and make sure the LED return
current path goes directly to the ground connection at that
electrolytic cap), and put a small resistor (scaled to drop maybe one
volt at max current) in series with the VCC line from the power
supply. This assures the VCC line (and the ground line!) won't see the
instantaneous current changes of the LEDs being turned on and off.
Also, keep this LED drive circuitry physically as far away as
practical from anything that handles audio signals.