Alt-BEAM Archive
Message #09241
To: beam@sgiblab.sgi.com
From: Wilf Rigter rigter@cafe.net
Date: Sat, 15 Jan 2000 19:23:20 -0800
Subject: [alt-beam] Re: D1
You did not mention a resistor in series with the LED. Your first report was : It
works! A 74HC14 with a +4V power supply driving a LED without current limiting
can probably source 50mA so the LED would be very bright for a short time. Do
you observe such a change in brightness? Have you tried a different LED?. Without
a series resistor it is possible that the LED was damaged after which it became
dim. A normal resistor value for that 4V supply voltage and a high effiiciency
(2mA) LEDs is 470-1000ohm. For less efficient LEDs use 100ohm which will result
in about 15-20mA initial current.
wilf
Bumper314@aol.com wrote:
> In a message dated 1/15/00 1:38:55 AM Mountain Standard Time, rigter@cafe.net
> writes:
>
> > Tell us a little about the connections of the LEDs, series resistors, the
> C1
> > size
> > and other circuit connected to the SIMD1.
>
> a 1F cap charged by a 5.5v solarbotics cell. 1n4148 diode. 74HC14 (i tried
> it will the HCT too). and the led is hooked up to V+ and the output from
> second inverter. after charging to 4v last night I set it solar cell face
> down and it glowed for over an hour but very very dimmly. Any thoughts
>
> Steve
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