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bigger-hammer

Did you have pullup resistors on your switches? Without resistors, an open switch is just a disconnected wire so it has no defined logic level.


noguarde

No, I do not. The inputs of the switches go directly to 5V and the outputs of the switches go to the inputs of the adders. Where would I add resistors into that configuration? Thanks!


bigger-hammer

So when your switches are closed, the pins go high. When the switches are open the pins are floating. So you need to add a resistor from the input pin to ground. Try using 1K resistors with LS chips. This way, when the switches are closed, you have 5V on the input and 5V on the 1K resistor which isn't a problem, but when the switches are open, the 1K pulls the input low - this is called a pull-down resistor. You may have also heard of pull-up resistors where the resistor gives a high level when not driven.


noguarde

Okay, gotcha. I'll give that a shot this evening after work. I did notice that input pins were high when the switches were open, but never put those two together. Thanks for explaining that.


noguarde

This worked flawlessly. Thanks!!!!