Re: Basic question about LEDs with USB chip
- From: feebo
- Date: Tue, 01 May 2007 22:31:37 +0100
On 29 Apr 2007 04:25:12 GMT, jasen <jasen@xxxxxxxxxxx> wrote:
On 2007-04-28, Dave <onlinefuel@xxxxxxxxx> wrote:
BTW a PIC will sink or source 25mA - the outputs are designed to
direct drive LEDs and 25mA is about as much current as you'll ever
need for a stock LED - I find I can get good brightness with much less
- hate LEDs so bright (as indicators rather than light source) they
make you squint.
One more question if you get around to it.
When you say 'direct drive', is it possible to not use resistors at
all to power 2 LEDs in parrallel? Thanks a lot for your help.
paralllel leds are unlikely to work with resistors, without, you have a
chance, if they are identical and you get the voltage right. In general
parallel leds are a bad idea
yes - well spotted... sorry put them in series
.
Relevant Pages
- Re: Controlling hundreds of LEDs
... >4017 at different rates from a pin of the parallel port would simply ... >make the 4017 cycle through the stages faster or slower. ... Connecting LEDs ... Since the duty cycle would be constant, the brightness would remain ...
(sci.electronics.basics) - Re: Digital Current Control for LED array
... >> brightness of all the LEDs should track. ... >you change the power supply voltage the brigtnesses will not track unless ... >match to be sufficient for small voltage drops in the resistors. ...
(sci.electronics.design) - Re: Controlling hundreds of LEDs
... Just note that different frequencies are ... There is no reason a single pin from your parallel port could ... Connecting LEDs ... necessarily change the brightness of each LED. ...
(sci.electronics.basics) - Re: Vehicles damaged by rising bollards
... normal current without flashing. ... controlling brightness. ... Even those white LED torches that you buy are flashing to increase the apparent brightness (the flashing is done by the LEDs themselves). ... I hadn't heard of this use of modifying the duty cycle of LEDs to make them "brighter" - other than in optical links where the receiver had little or no persistent vision. ...
(uk.legal) - Re: Vehicles damaged by rising bollards
... normal current without flashing. ... power output there is no apparent brightness difference between any kind ... Another application where there is no need to control the brightness. ... varying the mark to space ratio of the driving current to the LEDs. ...
(uk.legal) |
|
