I have a 1Khz clock and a one second gate time which feeds a four
digit display. The one second clock is counted by a four bit counter
to give 1, 2, 4, 8, seconds delay using diodes and a switch to select
1 to 16 seconds.
The display is four digits fed from the 1Khz clock gated by the 1
second clock. This is started by a monostable triggered from the
delay timer and triggered back by the stop button.
This works fine. I just don't seem to be able to see the wood for the
trees !
---
For some reason I didn't get your email addy, so if you'll send it
again (or post it here with sufficient munging to foil the
harvesters) I'll be able to send you my circuit.
BTW, here's the PRSG in LTSPICE, with a fix so it has a minimum
delay of 1 second (the "feature" was fixed
:
Version 4
SHEET 1 2076 1144
WIRE 480 -816 -352 -816
WIRE 592 -816 480 -816
WIRE 752 -816 672 -816
WIRE -416 -768 -592 -768
WIRE 240 -752 -352 -752
WIRE 240 -704 240 -752
WIRE 592 -704 240 -704
WIRE 752 -704 752 -816
WIRE 752 -704 672 -704
WIRE 240 -640 240 -704
WIRE 240 -640 -352 -640
WIRE 0 -608 -352 -608
WIRE -416 -592 -528 -592
WIRE 0 -592 0 -608
WIRE 592 -592 0 -592
WIRE 752 -592 752 -704
WIRE 752 -592 672 -592
WIRE -256 -576 -352 -576
WIRE -592 -528 -592 -768
WIRE -528 -528 -528 -592
WIRE -256 -496 -256 -576
WIRE 592 -496 -256 -496
WIRE 752 -496 752 -592
WIRE 752 -496 672 -496
WIRE -128 -480 -384 -480
WIRE 128 -480 -128 -480
WIRE 368 -480 128 -480
WIRE 512 -480 368 -480
WIRE -384 -432 -384 -480
WIRE -128 -432 -128 -480
WIRE 128 -432 128 -480
WIRE 368 -432 368 -480
WIRE -544 -384 -544 -464
WIRE -464 -384 -544 -384
WIRE -256 -384 -256 -496
WIRE -256 -384 -304 -384
WIRE -208 -384 -256 -384
WIRE 0 -384 0 -592
WIRE 0 -384 -48 -384
WIRE 48 -384 0 -384
WIRE 240 -384 240 -640
WIRE 240 -384 208 -384
WIRE 288 -384 240 -384
WIRE 480 -384 480 -816
WIRE 480 -384 448 -384
WIRE 752 -384 752 -496
WIRE -496 -336 -624 -336
WIRE -464 -336 -496 -336
WIRE -208 -336 -240 -336
WIRE 48 -336 16 -336
WIRE 288 -336 256 -336
WIRE -624 -320 -624 -336
WIRE -496 -256 -496 -336
WIRE -240 -256 -240 -336
WIRE -240 -256 -496 -256
WIRE 16 -256 16 -336
WIRE 16 -256 -240 -256
WIRE 256 -256 256 -336
WIRE 256 -256 16 -256
WIRE -624 -208 -624 -240
WIRE -384 -208 -384 -288
WIRE -384 -208 -624 -208
WIRE -128 -208 -128 -288
WIRE -128 -208 -384 -208
WIRE 128 -208 128 -288
WIRE 128 -208 -128 -208
WIRE 368 -208 368 -288
WIRE 368 -208 128 -208
WIRE 512 -208 512 -480
WIRE 512 -208 368 -208
WIRE 752 -208 752 -304
WIRE 752 -208 512 -208
WIRE -624 -176 -624 -208
FLAG -624 -176 0
SYMBOL Digital\\dflop -384 -432 R0
SYMATTR InstName A1
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL voltage -624 -336 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(0 5 0 50e-9 50e-9 .5 1)
SYMATTR InstName V1
SYMBOL Digital\\dflop -128 -432 R0
SYMATTR InstName A2
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\dflop 128 -432 R0
SYMATTR InstName A3
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\dflop 368 -432 R0
SYMATTR InstName A4
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\xor -400 -720 R180
SYMATTR InstName A5
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\and -384 -672 M0
SYMATTR InstName A6
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\xor -496 -480 R90
SYMATTR InstName A7
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL res 688 -832 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R1
SYMATTR Value 160k
SYMBOL res 688 -720 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R2
SYMATTR Value 80k
SYMBOL res 688 -608 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R3
SYMATTR Value 40k
SYMBOL res 688 -512 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R4
SYMATTR Value 20k
SYMBOL res 736 -400 R0
SYMATTR InstName R5
SYMATTR Value 330
TEXT -584 -184 Left 0 !.tran 20
When you run it, The horizontal axis corresponds to successive
pressings of the START switch (after the STOP switch has been
pressed) and the vertical axis corresponds to the numerical value of
the shift register's output, where 10mV = 1, 20mV = 2, and so on.
The resistor network is a DAC used to generate the vertical data and
isn't used in the actual circuit.