A powerful robot awaiting for a verbal command to crush its foes might sound like something from a science fiction film, but now it’s a permanent fixture of the [Making Stuff] garage. (Video, embedded below.) Thankfully this robot’s sworn enemy are aluminum cans, and the person controlling it with their voice isn’t a maniacal scientist, just a guy who’s serious about recycling. Well, we hope so anyway.
The star of the show is a heavy duty wall-mounted can crusher that [Making Stuff] built from some scrap steel and a pneumatic cylinder hooked up to the garage’s compressed air system. A solenoid operated valve allows an Arduino with attached ESP-01 to extend the cylinder whenever the appropriate command comes over the network. In this case, the goal was to tie the crusher into Google Assistant so a can would get smallified whenever one of Google’s listening devices heard the trigger phrase.
Obviously, those who’d rather keep Big Data out of their recycling bin don’t have to go down the same path. But that being said, having to give a specific voice command to activate the machine does provide a certain level of operational safety. At least compared to trusting some eBay sensor to tell the difference between an aluminum can and a fleshy appendage.
After crushing a few cans with his new toy, [Making Stuff] noticed a fairly troubling flaw in the design. Each time a can was crushed he had to reach into the maw of the machine to push its little flattened carcass out of the way. In other words, he was one bad line of code away from having one good hand.
The solution ended up being a new hose that runs from the exhaust port of the valve to the crushing chamber: once the cylinder retracts, the air exiting the valve pushes the crushed can out the rear of the machine and into a waiting pail underneath. Very slick.
We’d never criticize somebody for coming up with a creative way to save a few bucks. In truth, pickings would be pretty slim around here if we deleted every project or hack where cost savings was a prime motivator. That being said, there’s still some things you should probably spend a few extra dollars on. You know, the essential things in life that you need to know will be safe and reliable, like your car and…your flamethrower.
At the heart of this flamethrower is a solenoid valve recovered from a Glade air freshener. Rather than spraying out the smell of lilacs, this valve has found a new purpose in life by squirting out butane from a pressurized can. The butane is then ignited by a spark gap made up two nails connected to a 300 kV boost coil.
[Steve] designed the frame of this creation in OpenSCAD, and printed it out in a single piece. It holds the butane can and solenoid in position, as well as keeping the nails in the proper orientation for the spark gap to function. Admittedly the head of his printed flamethrower does look very cool, but if there was ever a situation where you should be suspect of the heat tolerance of 3D printed plastic, a flamethrower is probably it.
What’s noticeably lacking of course is any method to keep the flame from potentially traveling back up through the valve and into the butane can. The high-speed flow coming out of the nozzle is probably enough to keep that from happening, but we still wouldn’t feel comfortable strapping his device to our wrist as-is.
[James Bruton] is well known for making robots using electric motors but he’s decided to try his hand at using pneumatics in order to make a fighting robot. The pneumatic cylinders will be used to give it two powerful punching arms. In true [James Bruton] fashion, he’s started with some experiments first, using the pneumatic cylinders from foot pumps. The cylinders he’s tried so far are taken out of single cylinder foot pumps from Halfords Essentials, costing only £6.29, around $8.11 US. That’s far cheaper than a commercial pneumatic cylinder, and perfectly adequate for this first step.
He did have to hack the cylinder a little though, besides removing it from its mounting and moving it to a DIY frame. Normally when you step down on a foot pump’s lever, you compress the cylinder, forcing air out the hose and into whatever you’re inflating. But he wanted to push air in the other direction, into the hose and into the cylinder. That would make the cylinder expand and thereby extend a robot fighting arm. And preferably that would be done rapidly and forcefully. However, a check valve at the hose outlet prevented air from entering the cylinder from the hose. So he removed the check valve. Now all he needed was a way to forcefully, and rapidly, push air into the hose.
For that he bought a solenoid activated valve on eBay, and a compressor with a 24 liter reservoir and a decent air flow rate of 180 liters per minute. The compressor added £110 ($142) to the cost of his project but that was still cheaper than the batteries he normally buys for his electric motor robots.
After working his usual CAD and 3D printing magic, he came up with an arm for the cylinder and a body that could fit two more valve activated cylinders to act as a working shoulder. A little more 3D printing and electronics, and he had 3 switches, one for each valve and cylinder. He then had the very successful results his experiment. You can see the entire R&D process in the video below, along with demonstrations of the resulting punching robot arm. We think it’s fairly intimidating for a first step.
The setup uses a Raspberry Pi at its core and a set of USB relay boards to turn the valves and lights on and off to the music. They wrote the program in Python and have posted it on their website to share.
They used common household solenoid valves because they are easy to control by relay, but unfortunately they are on/off only, so variable flow is not possible. A challenge they encountered was equalizing the water pressure — one to make sure the pump didn’t over heat when the fountains were off, and two, to equalize the height of each fountain stream. To solve this they used a pressure regulator for the pump, and organized the plumbing in such a way with additional control valves that the pressure differences were minimal.
The setup doesn’t sound like it cost that much, and now the family has their own music activated water fountain in their garden — how awesome is that! Stick around after the break to see it in action.