Testing is done for now. Quick synopsis (TL;DR), don’t get rid of the resistor if you want batteries to last. I tested with the full PWM values from 1-255 and then halved them to range from 1-128 (see chart 1). I quartered them as well but ended up not using it because the half ended up disappointing.
Chart 2 shows the average current versus the resistor value for the different PWM values.
Lastly in Chart 3, I measured the light output of the LED. If anyone cares, using a Sekonic L-508 spot meter.
What this is showing is that no matter which resistor value (or no resistor) you pick when using a lower output PWM, it will never match the light output of the full range PWM values with the existing 220 ohm resistor.
Bottom line, if you want to keep the same quality of light output, you can’t change the PWM to a lower duty cycle.
Oh man this is the best post ever. LOOK AT THOSE GRAPHS! CHECK OUT THAT DATA!
Have an amazing project to share? Join the SHOW-AND-TELL every Wednesday night at 7:30pm ET on Google+ Hangouts.
Join us every Wednesday night at 8pm ET for Ask an Engineer!
Learn resistor values with Mho’s Resistance or get the best electronics calculator for engineers “Circuit Playground” – Adafruit’s Apps!
Maker Business — Transforming Today’s Bad Jobs into Tomorrow’s Good Jobs
Wearables — Make it snow
Electronics — Pseudodifferential Measurement
Biohacking — Soft Artificial Human Heart #3DThursday #3DPrinting
Sorry, the comment form is closed at this time.