A mint tin that gets angry when his mints are taken!
I was thinking about video game controllers, and what fun parts there are inside them. In particular, they have really nice buttons and analog sticks to be salvaged. It then occurred to me that there’s something even cooler in them- vibration motors! I’d been wanting to do something with a mint tin for a while, and I thought that making it vibrate unexpectedly to startle people could be some good wholesome family fun.
Mintzilla is a mint tin that notices when mints are removed, grows quietly resentful for a while, then lashes out in anger by buzzing futilely around the table.
You turn him on before going out for dinner/drinks/etc with your victim. When the time is right, you offer a mint, close the tin, and put it down on the table. Imagine their shock when, minutes later, in the midst of pleasant non-mint-related conversation, Mintzilla springs to life and buzzes in a furious rage!
Here’s a video demo of Mintzilla expressing his pitiful outrage at the selfish humans.
Alright, let’s see how he works! First, the schematic:
Now let’s look at the construction:
Here’s a little test-run. Note that the 555 is configured with a much shorter (two second) duty cycle for testing. It’s not fun to sit around staring at the breadboard for two minutes, waiting to see if it worked.You can see that when the photoresistor is exposed to light, there’s a delay, then the motor begins running. Since the delay is short for this test, you can also see how the motor is pulsed by the 555 if left running. In the final circuit, this would not occur, since the pulse is very long, and you wouldn’t want to let it run for a full cycle of the 555. Two minutes would certainly burn the motor out.
So, ready for final assembly, right? Well, that’s what I thought too. I made a real rookie mistake, though. I had intended to (and budgeted space for) a pair of coin cells to get the 6V needed to run this dog and pony show. I knew from testing that the motor needed about 180mA, so the 2N3904 can drive it with no problem. The coin cells would go dead pretty quickly with that kind of draw, but the motor will only run for a couple of seconds at a time, so it should be fine, right? Wrong. The veterans and pros reading this are laughing right now, because they know you can’t draw 180mA at once out of a coin cell. Or, frankly, anything smaller than a AAAA alkaline cell. Sure, the coin cells I have are rated for 240mAH, but the maximum continuous draw is more like 7mA. When I tried to drive Mintzilla with my coin cells, I got…. nothing. It was sort of neat hooking up a voltmeter and watching the potential on the cells drop to zero immediately as the motor tried to draw enough current out of them to start. The cells would recover once the load was removed, but the motor would never get going.
After doing my homework on battery drain, it was clear I needed something much bigger- like a 9V. However, that was too big and had more voltage than necessary. What I really needed was two thirds of a 9V battery.
So that’s precisely what I used:
There you have it! Be careful out there, and don’t make Mintzilla angry!