V1 Introduction to KT2 (kickstarter quadruped)

[Alan Timm]

I hadn't realized that it was possible to make a 1dof quadruped but here we are.

I'm not posting this to recommend it, but to say how easy it would be for any one of us to recreate the design.  It's cute but I fee like it could be redesigned to be even smaller.  enjoy.

https://www.youtube.com/watch?v=-jo0ZcBD9yA

[Chris Albertson]

of course now that someone has pointed out that you can build a 1-DOF quad, replicating that idea would only require 4 cheap $9 servos and for a prototype you would make a long cable to the electronics.  You could literally use hot glue to stick four sevos into a brick and srew sticks to the servo horns and have a working quadruped in 15 minutes.

Lots of credit has to gop t=o the person who figured out this could do something interresting.

OK, yopu could build it but could you make it walk?  It would not be a natural gate at all.     Legs motion has two phases.  Stance phase when the foot is in contact with the ground and a swing has when the foot is in the air, moving forward.  The question is how to lift a leg off the ground.  It seems they do that my using two diagonal legs to lift the robot body and the other two legs with it.

This is relly interresting as a beginner project.   We usually bud a diferential drive mobile platform because it is the easiest thing to build.  But this could be done, at least the mechanical part, for under $20 in an hour or so.

<meet kt2 kickstarter.jpg>

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<meet kt2 kickstarter.jpg>

[Chris Mayer]

The servos are interesting - looks like they are 360, like an SG90-HV, but they can also set a specific position like a regular PWM servo?  I didn't know these existed.  Or do they?

[Chris Albertson]

On Aug 8, 2024, at 10:50 AM, Chris Mayer <cmay...@gmail.com> wrote:

The servos are interesting - looks like they are 360, like an SG90-HV, but they can also set a specific position like a regular PWM servo?  I didn't know these existed.  Or do they?

Yes, you can buy them for between $15 and $20 on Amazon.  Go to Amazon and look up “‘serial bus servo”.  “Hi Wonder” is the maybe the top supliers of these.   Software to run them is on their google drive page.

But this picture shows what that can do.  What is good about them is you only need one bus to control all four servos.  (in theory up to 256 servos but that is not realistic)

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[Chris Albertson]

On Aug 8, 2024, at 10:50 AM, Chris Mayer <cmay...@gmail.com> wrote:

The servos are interesting - looks like they are 360, like an SG90-HV, but they can also set a specific position like a regular PWM servo?  I didn't know these existed.  Or do they?

You can modify almost any servo to turn them into simple gear motors by removing the internal PCB and removing the physical stop.    But the resistive position sensor will still only work within the old range.     To use them both ways at once you’d need to use your own microcontroller in place of the built-in one.    

You can also buy “serial bus” servos that come like this from the factory for $17.      But I have not seen them in the micro size.   These servos are a little like Dynamical servos but the price and size of the standard ones.  

[Chris Mayer]

Cool, thanks!  I like that we can swap legs for wheels to quickly convert from a JARR to a walker.  

Maybe even have a 2 DOF leg with the knee just inside a wheel's OD so the robot can bend it's knee and have both functions!

Looking at their videos it looks like they use something else as they aren't daisy chained together and have an SG90 size.

I did discover cheaper servos with a 4th feedback pin, and also some YouTube tutorials on how to easily solder a feedback pin to the center of the potentiometer, thus converting a 99 cent servo. If anyone buys one, I'd love to see what they actually use.