Simple way to count darts thrown (not keep score).

I'm looking for a way to simply count how many darts are thrown. I was thinking of using a microphone to listen for the "thud" on the dartboard. Is there a better way?

What would be a good way to eliminate external sounds from affecting the microphone?

I plan to use three 7-segment displays for the counter. And a button to reset.

If I run all of this off a 9V battery, what would be the estimated lifetime of the battery? I have no idea if it'll run for 30 minutes or 30 hours on a fresh battery.

Thanks.

Piezo ("knock sensor") behind the board.

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spycatcher2k:
Depends on the current draw of YOUR circuit & the capacity of YOUR 9V battery, but as you have told us nothing about either then how would you expect anyone to know.

True.
Standard Duracell 9V.
Using a piezo sensor (thanks wvmarle) and three 7-segment displays.

Just looking for an estimate ballpark figure. If I'm changing the battery every hour then it's not feasible for me to do this.

Such a small battery can probably not supply enough current for all your LEDs. Use a few AAs instead, or a 5V power bank.

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I'd use accelerometer for darts detections.

spycatcher2k:
What one? I see 3 types available! Also WHY? you have a 5V device, and you want to burn off 35% of your power for nothing.

OK! What is the current consumption you have chosen for these 7 segment displays? What microcontroller set are you using? e.g. An UNO? a stand alone ATMEGA-328? What drivers are you using for the seven segment displays?

I would use a stand alone 328, 3*AA batteries, driving the segments using 74HC595s, expecting to get 12-24 hours continuous use.

On a 9V PP3 battery with 350mA capacity, I would expect 3-4 hours.

Thank you for the estimate.
Since I can't answer all your questions I see I have more to learn than I had originally thought. I'll look further into this and see if it's something I should even bother tackling.

From a practical view it must be a bother not being able to find someone to count to three.

One...Two...Four!

Three Sir!

And they weren't even drunk.