DIY Prop Controller for $25 USD

November 15, 2016
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Custom Prop Controller PCB

For animated props more complex than your basic ghost attached to a gear motor, you need some way to give it life – this is where your prop controller is going to come into play.

I spent a couple of months this summer developing my own prop controller. It provides similar functionality to some of the better known mainstream brands, at one-third the cost. In this post, I will provide you with all the information you need to have to build your own board, including schematics, parts lists, code and enclosure. From here on out I will simply refer to the Mini Prop Controller (my name for it) as the “MPC”.

While the component costs vary slightly over time, at the time of this writing you should be able be build three boards for $75 – maybe cheaper depending on where you get your parts, and if you can split the board production costs with someone else (if you need less than three) you can do it for about $25 a piece.

Here’s what my design has to offer:

  • 1x Trigger Input
  • 2x 5 Amp (DC) Relay Outputs
  • Up to 68 Seconds of Animation
  • Up to 68 Seconds of MP3 Audio Playback
  • 3 Watt Internal Amplifier (Stereo)
  • Audio Line Out
  • Can provide external 12v power to other devices
  • Operates from a 12v 1A power supply


The ATTiny85 Microcontroller

Atmel ATTiny85 Microprocessor

The heart of this prop controller is the ATTiny85, a cousin to the microprocessors used on the Arduino boards (i.e. ATmega328P on the Arduino Uno), and a much cheaper alternative. When I first started working on this project, the ATTiny85 was $1.85 on Mouser.com. It requires no special external hardware for timing, such as an oscillator crystal, and its 8-pin footprint make it very agreeable for placement on a PCB where space is always tight.

The greatest challenge in this project was trying to figure out how to manage all the I/O on only five pins. I had to figure out how to send serial commands, control two relays, control the indicator LED, and detect input from four tactile switches (buttons) using only five pins.

The DFPlayer Mini MP3 Module

DFPlayer Mini MP3 Player

The DFPlayer Mini is a low-cost MP3 hardware module I used to incorporate sound into my board. I bought it for $7 USD off of Ebay and they’re relatively easy to find. It requires the use of a separate micro SD card for storing whatever track you want to play whenever the animation is triggered.

The DFPlayer is controlled via serial command output from the ATTiny85. The audio quality is very good for being such a small, low voltage decoder and amplifier. It comes with a powered stereo outputs (~ 3w each channel) and stereo “line out”. I was originally suspicious of the powered outputs, thinking they would be too wimpy to be of any use, but it turned out not to be the case. On Halloween night this year I used the powered outputs with a single 3″ speaker and it was just right.

Resources

Here are a number of resources that will help you build your own MPC:

Order this board from OSH Park