Programming/wiring an Arduino countdown? :)

[Scott.Burns]

@Christopher

If you didn’t have the resistor in the left schematic, the pin would just be floating. However, with the resistor in there, and the switch open, the path of least resistance is to V+ (compared to arcing across the air gaps in the switch to go to ground) and would register HIGH. But when the switch is closed, then the path of least resistance is through the switch to ground instead of through the resistor to V+, registering LOW. Did I reiterate this correctly?

You got it!

[Christopher]

Awesome! So helpful

[chris1]

This is a classic trap I have fallen into. I was prototyping something once with a shift register, which requires an annoyingly large number of connections, so I only hooked up the minimum necessary for my application. I spent an inordinate amount of time trying to figure out why it wasn’t working properly when I eventually realized I had left the RESET pin unconnected. I had no use for the RESET pin, so it didn’t even enter my mind as I was going through everything again and again… ok: power, ground, enable, latch, data… but the damned reset was floating and of course that means the chip is welcome to randomly reset on a whim.

[JeremyNielsen]

Guys! This is amazing. Thank you soooo much for the help! Sorry I haven’t been responding. My life just got flipped upside down (got a bill the size of half my annual income… Yay for misfiling taxes…) but I ended up just animating a countdown to play on the screen. Haha. But eventually (when I have the time to think about this again haha) I plan on making these!!
Thanks again! I love this community

[ihermit2]

Ouch. good luck with the tax people. Maybe you can offset the amount they say you owe with some expenses you didn’t claim or donations?

[JeremyNielsen]

I tried that route. Haha. Nothin really panned out. Haha. Good thought though!

[paulw]

Good luck on the taxes! (This is a time when, if you can, a good accountant is definitely worth the cost, both because of what they do and because of what you don’t have to…)

I once got a tax bill for about 3X my annual income, but that was back in the paper days when writing something in the wrong column could lead to really interesting results.

[ian]

Edited the typo in the title

[JeremyNielsen]

Thanks!