In comparison with using MC4011 NAND gate and tie two NAND gate forming a flip-flop as data selector. 74HC221 has alreday build in dual mono-multivibrator is much easier. Is that true?
- posted
18 years ago
74HC221 application
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- posted
18 years ago
-- Maybe. What are you trying to do?
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18 years ago
What I am trying to do is simply a data selector. Either a or b. In order to drive red or yellow LED and select a or b oscillator(MC4060),
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- posted
18 years ago
--- This should work:
(View using a non-proportional font like Courier:
Vcc | [R] | |A [LEDB] | | OSCA>---|-----------A _ | nand Y--+ A/B>----+-----------B | | +--A +--A nand Y--->OSC OUT |nand Y--+ +--B +--B | | +--A | |nand Y--+ OSCB>------------|--B | [LEDA] |A | [R] | Vcc
The gates are all NANDs (a quad dual input nand like a 74HC00 will give you all the gates in a single package) and comprise a 2 line to
1 line multiplexer. _ When A/B is high, the signal appearing on OSCA will appear at OSC OUT and LEDA will light. If you use a 5V supply, HC logic and high-efficiency LEDs, like an HLMP-4700 for the red and an HLMP-4719 for the yellow, the current limiting resistors will be:Vcc - Vf 5V - 2V R = ---------- = --------- = 1500 ohms If 0.002A _ When A/B is low, the signal appearing on OSCB will appear at OSC OUT and LEDB will light.
-- John Fields Professional Circuit Designer