ATtiny85: Make sure it’s through-hole.

Otherwise the coin cell can’t provide enough voltage to make any noise.

Buzzer: must have a diameter of 23 mm and (Important!) be rated at 3V or less.You can find it on eBay by searching for ‘Pushbutton 3A/125V’. Pushbutton: must be the one in the picture (with a 16 mm diameter thread), or else it will be difficult to attach to the upper hole.You can make a trip to a local electronics store, but I recommend buying on eBay from Hong Kong sellers (usually the cheapest in low quantities) for most parts.

Usually this is a very bad design choice, because cables are not made to dangle or be under stress, but for an application like this it’s reliable enough.

Notice that the board is dangling inside the enclosure, with the cables acting as dampeners.

I solved this by soldering a 220 ♟ capacitor between positive and negative, which acts as a power buffer during those interruptions (a filter, basically). This causes the microcontroller to lose power and reset, so the explosion never happens.

Notice that, in the perfboard, there is a coin cell battery fitted inside a battery holder? The instant the grenade hits the floor, contact between battery and battery holder is lost multiple times due to vibrations, even if it’s just for a fraction of a second.

They’re not really heavy duty but for now will do.

After having trouble with others I tried the one listed below, which gave good results while still being cheap.

A pushbutton has moving parts inside which may break after a good hit.

Electronics too have ways to protect themselves: If you remember the previous entry, there was a section talking about how to protect the sound grenade against impacts against the floor. Could it be done with a simpler and more robust solution? Sure.

I decided to use an ATtiny85 microcontroller and the Arduino environment because 1) It’s relatively easy for people who know little about electronics and C++, and 2) It allows me to change the behavior at any time by editing the code (such as increasing the countdown duration or disabling warning beeps). For instructions on how to make the 3D-printed enclosure, check out Sound grenade for Airsoft. Let’s get started on the second part of the sound grenade build, this part focusing on soldering, programming and assembling the electronics into the enclosure.

Arduino airsoft bomb code