Built November 2016
First I want to clarify this is NOT my design. It is from this great model on Thingiverse. Just wanted to clear that up first thing. I liked the design and just added to it with the face and back bone / cover.
I had the urge to build something quite simple to just build a robot and realizing I had not built a two servo walker thought it was worth a try. I have build three servo versions like the White Legged Spider Monkey and Farthing, and all my four servo walkers like TED, NED, Sir Robert, Eyer, SteamPunked, etc. but never a simple two servo bug type.
I decided to see what was available already out there to build and just add my spin on and ran across the Mantis Walker Robot by RobotShed. It looked pretty cool, was fully printable, I had green filament on hand so I printed out the part and then added a few of my own.
The only thing I really did different / added to it was to mod the 9V battery holder to handle a couple paralleled 3.7 240mah lipo batteries I had on hand and build out a new face for him. Otherwise the model printed great and assembled with a couple m8 allen head bolts. I still may design and print my own legs at some point that are more “Praying Mantis” looking but this should get him walking.
My Other Changes
I also decided early on that I didn’t want all the wires spewing all over like the Thingiverse version has and I wanted to add a couple other features to Manty. Early on I decided to use an ATiny85 for the CPU as they are super small, low enough power and I really only needed a few input/outputs to do what I wanted. Taking my Tweety Bot base code, I am reusing the code for the light sensor and speaker output. I am also paralleling the small yellow LED across the speaker output to get some light action along with the sound effects. I am using an old speaker out of some old iPhone so the volume isn’t great but it should make some clicks and chirps hopefully along with some light.
Pin Outs and Uses
1 (5) – Reset – not used
2 (3) – Sonar – single pin use
3 (4) – Speaker Output
4 ( ) – Ground
5 (0) – Front Leg Servo
6 (1) – Rear Leg Servo
7 (2) – Light Sensor
8 ( ) – +Vcc
The nice thing about an ATiny85 is they are, well tiny. It was easy to drop the chip on a socket into a small old round perf board from Radio Shack I had. I did put the Tiny85 in a socket as I have to pull it out over and over to update the code. I decided to hardwire everything instead of using header pins or connectors just to keep in cleaner. Problem if something dies or doesn’t work but he’s not overly complicated anyhow.
As you can see from the pin uses he has a little more function that the Thingiverse version. He can make sounds and light up his light (at the same time only), he also knows what the currently light level is and can stop and be quite in the dark and more active in the light.
As noted I wanted to use a couple little lipo batteries I had so a stretched the battery holder, enclosed it and made it shorter to hold the smaller batteries. I also wanted an on/off and charging port so I glued up a switch with a three pin header up under his front chest area for that purpose.
Hiding the Wires and Stuff
I didn’t want the wires showing everywhere but also didn’t want to completely change the design so I came up with a simple back bone cover soltuion. It works and the wire are pretty hidden but it can still be pulled off from the glue on if really needed.
The cpu fits nicely up inside the rear portion of Manty and the wires run down his spine under the covers I made to pretty much hide most of the wiring.