Comments on: Lowering power consumption tip #2 – modulate LEDs

By: shg

shg — Fri, 27 Jan 2012 14:02:49 +0000

There’s also another method of reducing power consumption. Use high efficiency (often marked with HE suffix) and reduce the current below 1 mA, or even less with low beam angle LED. I really have no idea, why designers are pushing maximal current through LED, are they want me to go blind?

By: Tom Evans

Tom Evans — Thu, 15 Oct 2009 12:10:23 +0000

LEDs that are turned off can consume power too.I remember a story about a board with LEDs connected to pins that were tri-stated when the LEDs were meant to be off. When light shone onto the LEDs they pushed the pins into their input threshold levels, resulting in a major (milliamp or two) increase in power supply current.

By: Tom Evans

Tom Evans — Thu, 15 Oct 2009 12:05:54 +0000

If you want to do ramp-fading of LEDs or one of those cool ramp-on-ramp-off activity lights, 8-bit PWM doesn't cut it at low illumination levels. You need 16-bit PWM to avoid a stair-step effect.

By: Nigel Jones

Nigel Jones — Wed, 23 Sep 2009 11:58:55 +0000

Agreed. I use devices from Taos for this. They work well.

By: GregK

GregK — Wed, 23 Sep 2009 08:05:35 +0000

Auto-magic brightness control (depend on brightness come up on screen) can be achieved by add some kind light sensitive element next to screen. Of course if you have spare pin with ADC.