I am using a SN74LS32N as an OR gate in a project, and I have hooked it up to an Arduino, but even when none of the inputs are powered, the LED that I hooked up to the output turns on. Why is this chip not working correctly?
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74LS32 is a LSTTL series chip (really DTL). If you leave the inputs unconnected they are effectively at "1". You need to ground each input to get a "0".
Each input has a 20K typical pullup resistor.
answered Apr 17, 2014 at 12:47
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\$\begingroup\$ If my inputs are grounded, how am I able to set them to 1? \$\endgroup\$– jonathanCommented Apr 17, 2014 at 12:57
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\$\begingroup\$ You need to actively pull them to ~0V with the Arduino outputs, not leave them open. \$\endgroup\$ Commented Apr 17, 2014 at 13:00
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\$\begingroup\$ Thanks. I was able to get this working with the OR gates, and an AND gate. \$\endgroup\$– jonathanCommented Apr 17, 2014 at 13:01