This particular IC is known a schmitt trigger inverter, this means that as soon as the input level reaches a logic-one level signal, the turn on is very fast (snaps on if you will), the output goes low.
Same with turn off, if you look at the hysterisis curve on the data sheet it shows it, although it will buffer the output of a printer port, you still restricted to TTL logic.
With buffers like the ULN2803 you can go up to 60vdc loads, to operate relays at 24v for e.g.
The printer port is not intended to drive any appreciable loads, so it is usually recommended to be buffered in some way.
If using external circuitry, the PC 5v or 12v supply can be used, as long as the load is withing reason and does not overtax the PC supply.
Al.
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CNC, Mechatronics Integration and Machine Design.
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E. |