Using A Vending Machine Bill Acceptor With Arduino

We’ve all seen, and occasionally wrestled with, bill acceptors like the one [Another Maker] recently liberated from an arcade machine. But have you ever had one apart to see how it works? If not, the video after the break is an interesting peak into how this ubiquitous piece of hardware tells the difference between a real bill and a piece of paper.

But [Another Maker] goes a bit farther than just showing the internals of the device. He also went through the trouble of figuring out how to talk to it with an Arduino, which makes all sorts of money-grabbing projects possible. Even if collecting paper money isn’t your kind of thing, it’s still interesting to see how this gadget works on a hardware and software level.

As explained in the video, a set of belts are used to pull the bill past an array of IR LEDs. The hardware uses these to scan the bill and perform some dark magic to determine if it’s a genuine piece of currency. [Another Maker] notes that these readers actually need to receive occasional firmware updates to take into account new bill designs. In fact, the particular unit he has is so out of date that it won’t accept modern $5 bills; which may explain how he got it for free in the first place.

Years ago we saw one of these bill acceptors used to make a DIY Bitcoin ATM. Of course back then, a few bucks would get you a semi-reasonable amount of BTC. These days you would skip the paper currency and do it all digitally.

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Chatty Coaster Agitates, In A Friendly Way

Awkward silences can be highly uncomfortable. Thankfully, they’re a problem that can be solved by technology. Chatty Coaster aims to do just this, detecting pauses in conversation and interjecting with helpful questions to move things along.

The coaster is built around an Arduino Micro, which uses a microphone to detect audio levels in the room. When it detects an extended silence, it then fires off a sound clip using a SparkFun audio breakout board. The questions vary from plain to politically sensitive, so there’s a good chance you could get some spicy conversation as a result. Any talking device runs a risk of being more annoying than helpful, and there’s certainly a risk that Chatty Coaster could fall into this category. Choosing the right content seems key here.

Overall, while this may not be the ultimate solution to boring company, it could get a laugh or two and serves as a good way to learn how to work with audio on microcontrollers. Video after the break.

We’ll admit, when we were reading this one, we thought we had déjà vu. But this one’s a lot less blamey.

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A Really Garbage Project

No matter who you are,  you produce garbage of some kind or another. Two students decided they wanted to create a smart garbage can that could alert them when the can is full or even when it is stinky.

We will go on on the record: we didn’t know that an alcohol sensor could tell if your garbage is stinky, so if that works, that’s a new one on us. However, it makes a certain kind of sense because garbage ferments. We thought garbage smelled because of hydrogen sulfide and methane.

Trash cans have a tough life, so if you really want to duplicate this, you’ll probably want to mount things a bit more securely. The software, however, runs everything through a cloud service and from there can use Blynk for a phone app and IFTTT to ship things to a spreadsheet, should you care to track your garbage history statistics.

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Self-Playing Whistle While You Work From Home

In ridiculous times, it can help to play ridiculous instruments such as the slide whistle to keep your bristles in check. But since spittle is more than a little bit dangerous these days, it pays to come up with alternative ways to play away the days during lockdown life.

Thanks to some clever Arduino-driven automation, [Gurpreet] can maintain a safe distance from his slide whistle while interacting with it. Slide whistles need two things — air coming in from the top, and actuation at the business end. The blowing force now comes from a focused fan like the ones that cool your printed plastic as soon as the hot end extrudes it. A stepper motor moves the slide up and down using a printed rack and pinion.

Here’s a smooth touch — [Gurpreet] added a micro servo to block and unblock the sound hole with a cardboard flap to make the notes more distinct. Check out the build video after the break, which includes a music video for “My Heart Will Go On”, aka the theme from Titanic. It’s almost like the ship herself is playing it on the steam whistles from the great beyond.

Speaking of, did you hear about the effort to raise and restore the remains of her radio room?

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Measuring UV-C For About $5

Looking to sterilize something? Give it a good blast of the old UV-C. Ultraviolet radiation in the shortest wavelength band breaks down DNA and RNA, so it’s a great way to kill off any nasties that are lurking. But how much UV-C are you using? [Akiba] at Hackerfarm has come up with the NukeMeter, a meter that measures the output of their UV-C sterilizer the NukeBox. It is built around a $2.50 sensor and a $3 Arduino.

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Automating Hand Sanitizer — If You Can Find Any

We once saw a Romeo and Juliet production where the two families were modern-day mob families with 3-piece suits and pistols. If they made King Richard III set in this week, the famous line might be: “Hand sanitizer, hand sanitizer, my kingdom for hand sanitizer!” Even if you have a supply stashed in your prepper cache, you have to touch the bottle so you could cross-contaminate with other users. Public places often have automatic dispensers to combat this, and now you can too. [Just Barran] shows the device in a video, you can see below.

Sourcing parts for projects is sometimes a problem, but right now we are betting the hand sanitizer will be the hardest component. Of course, the Internet is ripe with homemade brews that may or may not be effective based on beer, grain alcohol, or a variety of other base materials.

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Another PC Power Supply Project

Economy of scale is a wonderful thing, take the switch-mode power supply as an example. Before the rise of the PC, a decent multi-voltage, high current power supply would be pretty expensive. But PCs have meant cheap supplies and sometimes even free as you gut old PCs found in the dumpster. [OneMarcFifty] decided to make a pretty setup for a PC supply that includes a very nice color display with bargraphs and other niceties. You can see the power supply in action in the video below.

The display is a nice TFT driven by an Arduino Nano. The project uses ACS712 current sensor modules, which are nice Hall effect devices that produce a linear output for current and have over 2 KV of voltage isolation.

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