25 Jun
2007
25 Jun
'07
1:31 p.m.
On 24 Jun 2007 at 22:18, Gordon JC Pearce wrote:
<mumble> years ago, I rescued much of the control electronics from some
kind of X-ray diffraction instruemnt. The parts I really wanted (and got)
were the paper tape punch and reader and the printer, but I grabbed the
electroncis units too.
The punch and reader are the mechansims from a Friden Flexowriter,
mounted on 19" rack pneals, with their own drive motors hehind. The
printer is a Comptometer adding machine (I am not sure if any mods were
done to it) with solenoids mounted over the key levers.
The control electroncis is all discrete transsitors on plug-in PCBs.
There are a couple of rows of DM160 valves [1] used as status
indicators. And one of the units has a plugboard on the front to
configure the instrument.
[1] I am not sure what the US equivalent is. It's a little glass envelope
about 1.25" long by .25" diameter. It has 4 connections, 2 of them are
the ends of a 1.1V directly-heated cathode, one is a target (run at about
+30V wrt cathode, the last is the control grid. With 0V bias on the grid
you get a bright green glow from the target (and thus from the side of
the valve), with -3V bias, it's cut off, and dark. They wrre used as
logic status indicators before there were LEDs.
-tony
I used to fit microwave links onto the tops of
tall multi-storey
buildings. The lift controllers I saw tended to run from a small rack
the size of a MicroVAX 3300, up to several wardrobe-size racks full of
relays.
Let's not forget interesting control systems in other devices, such
as jukeboxes (Seeburg used core memory, I believe), scoreboards and
combination actions in pipe organs.