Electronics Projects, Expansion to 32 Channels Parallel Port 74HCT573 LPT Relay article
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I previously shared circuit “Computer with Device Control” writing output thanks to the integrated circuits have been replicated so 74hct573 (32) also with source code control program has two This circuit allows connecting up to four power control modules to the same parallel port. This port need not be bidirectional, so any PC oldest will be to control this system.
The soft PC can be written in the language you want, provided that it has the ability to use the parallel port of the PC. Since we know that the state is parallel and hence our expansion board, the first thing you have to do is initialize the soft circuit. For that, set to 0 the data bus parallel port, so that all its pins (2 through 9) are grounded. Then wait 10mS for the data entries is set to integrated. Actually, with 1mS is more than enough, but as the weather here better give us spare some extra time. After the 10mS after activate the four integrated setting high four control pins of the parallel port. Then waited another 10mS for the latches retain data on outputs and finally put low (zero) all the control pins of the parallel port so that the integrated outputs left on all the pins off (ground) regardless the data that appears in your posts from now on. With this module will be initialized and all outputs off.
LPT Port Relay Circuit
Also in 74hct573 based on the output of the control board to control devices required for high power driver circuit to output information about the 74hct573 given in opto, triac or relay can connect by adding ULN2803
source : pablin.com.ar LPT control circuit Power control for PC circuit program files
alternative link: expansion-to-32-channels-parallel-port-74hct573-lpt-relay.rar alternative : link 2