I have a Useless Machine by Spikenzie Labs, and it's been very entertaining for my kids and I, but it does the same thing every time and gets old quickly. I wanted to build a programmable, Arduino controlled useless machine that has an attitude. I've seen many online, but couldn't find a kit, so I set out to build one.
Since I'm new to using servos, I wanted something that would "just work", so of course I turned to Adafruit. I've been wanting to try out their new line of Feather microcontroller boards, and saw that they now have a Servo FeatherWing (shield). I debated which Feather board to use, and decided on the 32u4, since it's fairly inexpensive, simple, and likely has the lowest power consumption. I don't need Wi-Fi, BLE, etc.
I really like the physical construction/layout and "animations" of this Useless Box by Sally71. I managed to find a Wooden Recipe Box at Michaels with similar dimensions. It seemed large enough to contain all of the electronics, and has a magnet to keep the lid closed instead of a latch like most of their other boxes.
My code is currently a heavily modified version of "Moody Useless Machine" by Lamja Electronics. I had to modify it to use the Adafruit Servo Driver library, change the pulse length (positions) for the servos I used, and my very different physical layout.
| Cost | Name | Description |
|---|---|---|
| $12.00 | TowerPro SG-5010 standard servo | Servo for the arm that turns off the switch. |
| $5.95 | TowerPro SG-92R Micro servo | Servo for the arm that opens the door/hatch. |
| $19.95 | Adafruit Feather 32u4 | Any microcontroller should work. |
| $9.95 | 8-Channel PWM or Servo FeatherWing | Any servo shield/breakout should work, and may not even be required. |
| $2.95 | 4 x AA Battery Holder with On/Off Switch | To power the servo shield. |
| $9.95 | Lithium Ion Polymer Battery - 3.7v 1200mAh | To power the microcontroller. |
| $5.99 | Wooden Recipe Box | |
| $3.49 | SPST Flat Lever Toggle Switch |
| Various bits of thin wood. | For servo support, arms, etc.
$70.23 | Total
I'm going to try to reduce the parts cost by $30 by replacing the Feather with a 5V Pro Trinket and omitting the Servo FeatherWing and lithium battery. I think the 6V (4 x AA) battery pack can power both the Trinket and servos. I might add a capacitor to prevent the Trinket from seeing a voltage drop when driving the servos.