murray@src.dec.com (Hal Murray) (08/03/90)
Years ago, somebody told me that the eye responds more if the available energy is clumped into bursts. This was during a discussion of multiplexing LEDs (or LED decoders). The idea was that multiplexing LEDs actually increased the apparent brightness for a given average current. I looked around, but didn't find anything to confirm this. Has anybody seen any charts eye response vs duty cycle? Any suggestions as to where I should look?
commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) (08/04/90)
murray@src.dec.com (Hal Murray) writes: >Years ago, somebody told me that the eye responds more if the >available energy is clumped into bursts. This was during a >discussion of multiplexing LEDs (or LED decoders). The idea was that >multiplexing LEDs actually increased the apparent brightness for a >given average current. >...Has anybody seen any charts eye response vs duty cycle? Any >suggestions as to where I should look? See _Modern Electronics_ magazine, June and July 1990, (Forrest Mims' monthly "Electronics Notebook" columns) for nice reference articles about LEDs, including the new high-output types. It doesn't have the specific info that Hal is looking for, but does discuss driving LEDs with high-current pulses: "...diode can be driven by current pulses having a peak amplitude of 300 mA, as long as the pulse diration does not exceed 1 millisecond and duty cycle remains below 5 percent. At 300 mA, the diode emits more than 10 times the optical power it emits at 20 mA..." -- Frank Reid W9MKV reid@ucs.indiana.edu
Nandu@cup.portal.com (Narendra J Kulkarni) (08/04/90)
If I remeber correctly, the persistance of vision allows eye to see the stabl e display ( flicker free ) even if the LED is pulse driven, The advantage of multiplexing is strictly for saving the components, actually at very high current, more current is wasted in heat generation in the LED, most LEDs have a linear region in which light output is proportional to drive current and by calculating the duty cycle one can determine the peak pulse current