[time-nuts] TNS-BUF update

Didier Juges shalimr9 at gmail.com
Sun Aug 19 09:15:57 EDT 2018


That's a very good point. I have used LEDs as photocells many times, the
first time was in 1974 when it was easier for this university student to
get LEDs than photocells.

I have also made a bi-directional optically isolated data link using a
single fiber optic cable and two fiber optic transmitters (LEDs) in the
HFBR-500 series.

A couple coats of black paint, or a dab of black epoxy covering the LED
should work. Include the back side of the PWB for good measure, this is
time-nuts :)

Didier KO4BB


On Sun, Aug 19, 2018, 3:38 AM Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

> --------
> In message <1818735266.3837388.1534666949194 at webmail.xtra.co.nz>, Bruce
> Griffit
> hs writes:
>
> >It exploits the fact that for a RED LED at least the difference
> >between the LED forward voltage and the transistor Vbe is ~ 1V and
> >has a fairly low tempco and has low noise (at  least for RED LEDs).
>
> ... in darkness.
>
> When using LEDs this sort of way, they should always be totally
> shielded from all external light.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
>


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