Electronics > Projects, Designs, and Technical Stuff
Is there a circuit for something like a 3-state monostable multivibrator?
Timmy73:
Is there? Im making a video generator (creates a movable and size-adjustable cursor on a composite TV set) and Im wondering if there is a circuit like a monostable multivibrator where its "off" for some time, then "on" for a while, then remaining "off" until the next trigger pulse?
I imagine there is something like a Ring oscillator that would do this. I would prefer that this circuit can be made with 3 discrete transistors.
Thanks,
Tim
ledtester:
Sounds like you want a "pulse delay" circuit.
You can make one with a CD4098 -- a dual monostable multivibrator. Here's the basic idea from the datasheet:
RJSV:
Perhaps way overbuilt, take a glance at my 2 IC plan, uh 3 IC plan. Photo diagram shows a pair of CD4017 counters.
Rotary switch, select your 'off time': then
That pulse coming, second CTR runs, timing out the 'ON timer'.
The 'TRIG in' acts as described, starting (both) CD 4013 back to '00'.
Rotary six POS, plus SPDT, will switch one of 12.
RJSV:
Here is better schematic, has two CD4017, and a 4013 (f/f pair).
Starts out '00', both f/f off, CTRs clear.
Then '01', TRIG in sets f/f 1, that allows CTR1 clock.
With '10', (read the bits rt to left). with count=7 the pulse clears f/f one, sets f/f 2. This allows the
CTR2 clock. Also used for your output.
See pinout, CE must be 0 to count.
R=1 to reset counter.
RJSV:
To avoid the 'TRIG' input from affecting the sequence, I made changes. This schematic features less IC count, by taking both types of counts, in one CD4017 IC.
First, notice the 'state 0' output is unused, as you need to time at least one (clock) count. Next, see the first f/f stays set, usual dual multi-vibrator circuit will also have some way of avoiding a re-trigger, until cycles complete.
Meanwhile, arrival at a first-count sets the output f/f, and a second-count times that (output pulse).
For example, you can set 3 clocks as first timer, that's 500 nSec. (6 MHz clock rate, from video sys).
Then, a second rotary switch, sets T2=3 clocks, also, for a 500 nSec output pulse (followed by all clear state.)
Of course, a 'bug' there, as the rotary settings should be overlapped. Plus, not ideal as rotary mis-settings are possible. Some 'glitches' might literally only cause a slight flicker, as this is for a screen curser timing...
Navigation
[0] Message Index
[#] Next page
Go to full version