29 Aug
2008
29 Aug
'08
1:30 p.m.
William Blair wrote:
If for some reason I can't get any of the most
common and cheapest
high B+ dual triode tubes to work in a logic circuit at low plate
voltages, then I'll have to go with something like the dual diode,
single triode "space charge" car tubes that aren't in demand by audio
enthusiasts making them much more readily available and much cheaper.
A functional hobbyist demonstration of tube logic that's cheap and
uses low voltages is my goal.
I've updated my web page about the ASM with some commentary about the gate
design, if interested (http://www.cs.ubc.ca/~hilpert/e/ABC/asm.html). Following
from what is written there, if one is setting out to
create a tube logic gate
design with resistive inputs I would lean towards a
positive-logic-NAND /
negative-logic-NOR approach where there is only one condition (input state)
driving the tube to saturation. Resistor values would still have to change
depending on the number of gate inputs.
Neon bulbs for each input were one of the other techniques used to avoid the R
problems (no help for a low plate voltage design obviously). "DVL" logic might
be interesting at low plate voltage.