Gadget Dreams…

I wanted to make a Biped Robot ‘from basics’ instead of a kit, using some sheets of metal that I could saw and bend myself, standard strong servos and an Arduino based development environment.

This is the result so far. It’s a work-in-progress, so I’ll probably make changes to it. The software isn’t done yet, but it can at least crouch and stretch, lift a leg etc.

Here is a video of it’s first steps. It fell forwards after the video was over. Will improve the software and then post it here later.

First steps

The version 1 plans of the robot are as shown on the image.

I basically cut along the solid lines and bend along the stapled lines. In fact I didn’t quite do it as on the plan, but it’s pretty close. There’s a full size pdf available here. The drawing is drawn using CadStd Lite and if you ask you can probably have the original file.
The main components are A and B. The servos are attached in A.

Some comments:

• Component A could be made a bit narrower (30mm/35mm/30mm instead of 35mm/35mm/35mm), which might help the servos a bit. The servo could be placed along the ‘wall’. Maybe other components could be optimized also.
• It’s quite tall (about 35 cm or about a foot). That together with no torso, makes it hard to balance. (and no feedback from servos).
• It requires 12 really strong servos. I’m using Power HD 1501MG, which is said to have 17kg.cm torque. The one that struggles the most is the hip that lifts the leg outwards. It might be that the design could be changed to make it easier for that servo.
• I used a 1mm thick aluminium sheet, but it can probably be done with other materials also, for example steel or plexi glass.
• I put some bigger feet on it to make it a bit more stable and easy to program, using plexi glass (see the picture).
• Cut it with a jig or contour saw, drill the holes and bend the pieces along the dotted lines (check YouTube on how to bend sheet metal without special tools). It doesn’t take long to make. Before you drill, use a nail and hammer to make a mark where you want the hole. This makes the placement more accurate and makes it easier to drill.
• The controller board is a self made AtMega328 board using Arduino as the development environment. It’s using 12 digital outputs to drive the servos. I’m using the servo library that’s part of Arduino. I can share more on the software later, but if you have questions or suggestions, please comment below.
• I’m using separate batteries for the servos and the electronics to prevent voltage drops caused by the servos to reset the controller. For the servos I’m using a 6V NiMH battery. These servos draw a lot of current, in total somewhere between 5 and 10 A. I wanted to use LiPo batteries, but they’re quite high voltage and will probably damage the servos unless I use a regulator. There are LiPo capable servos, but they’re quite expensive.

If you want to try also, please go ahead using the Attribution + Noncommercial + ShareAlike (by-nc-sa) Creative Common License. Let me know if you have improvements, questions or comments. If you want to make your own biped robot and you find the kits too expensive, this is the way to go. It works, it’s not toooo much work and you learn a lot.
If you’re wondering where the parts go, here’s a picture trying to explain it.

I’ve used a 1mm thick aluminium sheet. It’s probably possible to use both steel and plexiglass instead. Some of the joints would benefit from thicker aluminium or steel.

As the project progresses, I’ll put in some more info here and maybe post a video and some code. If you have comments or questions, please post. I’ve got an antispam on that may make your comment take some time to appear.