Michel
Ambient light based brightess control is something I have been playing
with. I remember, as a nipper, we had a valve B&W TV set with a LDR in
the front panel so it had a sort of "automatic" brightess control.
But I would certainly do the control by varying the grid voltage wrt the
cathode not by varying the heater/cathode temperature. My
understanding, although I don't know the physics involved, is that is
bad to underrun a heater. Overrunning is perhaps more obviously wrong.
The main problem I have at the moment is that as the beam current is
varied it pulls the focus off, adjust the brightness, adjust the
focus... I've not gone far enough into finding out whether its the true
CRT charactertics that are doing it or my crap PSU being pulled around :(
Cheers Grahame
On 11/12/2012 21:15, Michel wrote:
Great design and source of information Graham! Fantastic.
Just wondering about 1 thing, is it possible to adjust the brightness
of the scopeclock according to the ambient light? Usually you would
use the control grid of course, but what it you would adjust the
current through the filament? It would both lower the power
consumption and increase the life of the tube, I would expect?
The IN9 / IN13 bargraph clock is my next project!! Tubes are on the
way but hope I will have some time to work on it :-)
Michel
On Dec 12, 12:51 am, Grahame Marsh <[email protected]>
wrote:
Hi
I have added a webpage where I test a variety of other small CRTs with
the scope clock 2 hardware.
http://www.sgitheach.org.uk/scope2a.html
This page will continue to carry updates as I trial other CRTs and other
PSU configurations. I'm still extending the range of clock faces and
adding multi language support.
The rubidium oscillator clock workover is completed and the designs are
all here. The complete software including the source code written using
the free GCC -AVR C complier is available for download.
http://www.sgitheach.org.uk/atomic.html
The Giant 7 "Jon Ellis" Segment Clock page now has the software (again
GCC-AVR) available for download.
http://www.sgitheach.org.uk/ss.html
Cheers Grahame
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