This is a cool mod that adds a bullet counter to an Airsoft rifle.

“The new circuit was built with the hopes that since the CMOS IC has much lower voltage requirement, it can still operate when the rifle is firing, but I was wrong. Though my second alternative is to use external batteries, and power consumption is an important factor in this case.

As far as power goes, the new circuit uses the Motorola 14533 CMOS to multiplex the three digit displays which saves a lot of energy from having to power all three digits at the same time. Only one LED driver is needed because of that instead of three. ”

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