Coin Acceptor

Posted: August 6, 2017
Updated:October 15, 2017


So... one of my friends contributed to one of my projects by giving me a couple of dolls that her daughter didn't want (I guess she knew the difference between a real Barbie and this dollar store trash). As of this post, I haven't finished that project yet (a poker game of some sorts) but another idea hit me while browsing SparkFun's website and looking at a Coin Acceptor. I wrote a little song, put some electronics together, hot glued some servos, and posted a video below. Hopefully people find this funny :).

The Music

This is a little 30 second clip I threw together early one morning. I simply wrote a drum line using Drums++ and imported it into Apple's Garage Band. Then threw a bass line under it and a rhythm guitar part with a Crybaby Wah Wah pedal both recorded line direct. Just for fun I also recorded a guitar solo over it recorded mic'd with a Digitech RP-55 into a small Bugera tube amp. I'll probably be using that as the base for a song for a future project. For the full mp3s:


This is not the only project I've written my own music for this year... I have a Singing Fish project that I never posted publicly.

Related Projects

Artwork: LED Pumpkin Candle, XOR Gate, Motion Eyes, Clay Figures, WS2812 LED, LED Panel, Half Adder, Gingerbread House, Cyborg Chicken, Electric Cat Fight, Iced Electronics


The first video I posted with the original circuit.

Here's an updated video which uses the blonde doll (as seen the Electric Cat Fight project) instead of the brunette. This video also demonstrates that the coin acceptor will reject a coin that isn't a US quarter. Even a Swedish krona, which is similar to a quarter, is rejected. The audio in this circuit is done with a SparkFun TPA2005D1 board.


I used a TI Launchpad board with an MSP430F5529 chip that I originally for a VGA Java project. I was originally trying to just use an MSP430G2553, but the only way to get the song to fit was to downsample it to 3000 samples per second, which sounded terrible. What's heard in the video is 11,000 samples per second. For a DAC I used an MCP4921 as I have for many other previous projects. Since I have schematics showing how to use that chip on other projects on my website, I decided not to post schematics for this one. The sound amplifier used here is an LM386, which again I have other examples of.

Now the coin acceptor :(. Oh boy. This thing had really really bad documentation. I found some other people explaining how to set it up so I just did what they said. The cable that comes with it really isn't the correct cable for this set up and falls out a lot. It was pretty awful to work with. That said, it did work. I originally had a video showing it rejecting a dime and only accepting a quarter, but that video didn't come out very nice and the coin acceptor factory reset itself after that from the cable partially falling out.

As for the doll, she's dancing in a shoebox (hence the song being called shoebox.mp3) which has a servo hot glued at the bottom with a wooden platform to stand on. Two more servos are hot glued to the platform and connected to her hands with paperclips I straightened out. The curtain, which is simply a paper towel I marked up with a Sharpee, is being controlled by a servo at the top which is connected to the paper towel by a popsicle stick and another straightened paperclip. And yes I know that "Free Show" is contradicted by "Insert $0.25".. it's supposed to be a joke.


Coin Acceptor circuit schematic

Schematic for the coin acceptor circuit.

Source code

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