On 08/03/2012 11:32, John Rehwinkel wrote:
I'd be tempted to make an old A-scope style radar display with a few
lines of shark-fin looking pips (hours, minutes, seconds), and have
the pips slowly meander across the screen. A few index marks would
make it easier to read. I don't know how hard that would be to code
up, but the existing displays cover a lot of ground, so I'm guessing
it would be feasible.
A-Scope:
Horizontal traversing pips/triangles, off a horiziontal line, taking (1
second,) 1 minute, 1 hour, 12/24 hours to go L/R or R/L - easy! I'll
code it when I have the pingpong clock finished.
I'm hoping to get a look at the code soon, idiosyncratic or not. I
have a fondness for strange real-time code.
I'll try to put the current draft code up tonight, so look back in about
24 hrs and the code.zip file should be there. Head straight to crt.c
and .h as that is where all the low level driver stuff is. Then look at
say, klingon.c and .h, and you'll see a simple case of how the lowlevel
stuff is called (each clock face lives in its own .c and .h files so it
should be easy to find an individual clock face's code). Then the main
code (sc01.c) where the clock face being displayed is called under 20mS
interrupt call. (BTW the 20mS is mains derived which I hoped would
avoid the display "swimming" in an external magnetic field as the clock
has no shielding. So far no problems.)
They don't? What are you using as rectifiers? I can imagine a 50Hz supply
with 5642s as rectifiers, but that would involve adding quite a few filament
windings to the power transformer.
Yes, I was being a bit loose, just 1N4004, semiconductors of course. No
chips or MOSFETS to fry is what I meant :o)
Which reminds me, the article mentioned adding a heater winding, but I didn't
find a description of how it was implemented.
The heater winding details are lost on the schematic. Basically about
120 turns for the toroidal transformer I used. I wind on a measured
length (1m typically) and count the turns and load it to 0.3A and
measure the voltage. I discard this length. This method gives me the
turns per volt and the total length of the wire to wind on. I add about
10% more and then trim back to get the 6.3V. I was thinking of putting
a bit of text on the webpage about it. The extra winding is "easy" on a
toroid and avoids a second transformer or special, so is cheap. I used
multicore hook up wire that has a > 1kV insulation (PVC) and a couple of
amps capacity so is overkill for the duty.
I think brass on both ends would look really sharp. I'd be tempted to make a
slide out light shade as well, either a hood like a traffic signal, or a tube
like the old Waterman pocket scopes. Not that it's necessary, but it's another
fun thing to fiddle with, if you actually want peoples' fingers near the CRT.
Only, I'm trying to close the project down to get on with the next! The brass
and copper is lacquered to avoid finger markers appearing - the copper tube
forms a natural handle to pick it up with unfortunately. The light shield is a
good idea, for this tube in particular, as it has no separate focus anode - the
brightness control is both brightness and focus, and the best focus is when the
tube is not bright.
I love the Latin markings too. Fiat lux, indeed!
My wife's contribution. Getting her to contribute to projects is my
technique (not always successful) that permit projects to leave the
workshop and enter the house.
Thanks for the feedback - as always very good with this group
Cheers Grahame
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