New Project – Convert The KHR-1 Robot To The RCB-3 Controller

Robot controller board RCB-3
Well, after a couple of months working with the new Kondo RCB-3 robot controller that came with Mondai-Noid, our MANOI AT01 robot, we have to admit that we've really become spoiled. Compared to its ancestor, the RCB-1, the new controller is actually fun to program and to see what we can make it do. It's a breath of fresh air.

It's not that the RCB-1 was that hard to program - it wasn't. But the RCB-3 is so much more powerful and easy to use that we find ourselves really looking forward to the chance to create new motion sequences and programs. At the same time, we found ourselves ignoring Gulliver, our KHR-1/RCB-1 robot. So, what would rekindle our interest in Gulliver, and make some drastic improvement in his KHR-1 level performance?

After a little thought, and checking back through our notes, we remembered that at the original RCB-3 pre-release seminar we attended at RT Corp. last Spring they mentioned that it 'might' be possible to use the RCB-3 with the KHR-1. There was some mention of a 'booster', but we were so excited about the new robot controller at the time that we didn't dig into the details.

It turns out that it is definitely possible to replace the two older RCB-1 controllers in the original KHR-1 humanoid robots with a single RCB-3 controller. And there are a multitude of reasons why we, and others, would want to make the swap. First, and foremost, is the ease of programming. Many of the features built into the RCB-3 and the Heart to Heart 3 application weren't even dreamed of when the RCB-1 was first designed. Things like the ability to scale, link, or mirror servo positions as a group, or to duplicate then quickly modify poses to create a complex motion sequence or scenario.


The RCB-3 controller handles up to 24 servos along with 3 analog sensor ports, plus high and low speed interfaces. Note - you'll see the Red Rabbit popping up all over the robot community since it's the corporate symbol for RT Corporation, a great source for robot training, kits, parts, and custom development.

We also expect to see a noticeable improvement in the robots motions since the RCB-3 should provide about 3X improvement in position control - at least that's what our initial estimates indicate. Hopefully we won't be disappointed. And the ability to use analog gyro sensor inputs to modify multiple servos should give Gulliver a lot more stability. We'll see.


The RCB-3 controller is surprisingly small. That 100 yen coin to the left is roughly the same size as a US quarter. Our only concern is our big fingers and the small spacing. Plugging all the servo and sensor connectors into the board is going to be challenging without a doubt.


The flip side of the robot controller doesn't waste a single square millimeter of space.

It turns out that the 'booster' is only needed if you want to mix the older standard voltage servos with the newer HV (high voltage) types. In Gulliver's case, all his servos the older, lower voltage, so the booster shouldn't be required (knock on wood).

We have a couple of other 'hacks' in the works for Gulliver that should really boost his performance and add several additional degrees of freedom, Hopefully we'll be able to free up some time to make them a reality during the upcoming Christmas/New Years holidays.

Related links:

RT Corporation Website

Kondo RCB-3 Introduction


3 thoughts on “New Project – Convert The KHR-1 Robot To The RCB-3 Controller

  1. Hello,

    I am new to robotics and I would like to make an attempt at building my robo one style robot. I have 21 futaba digital servos. The specs say that they are Pulse WidthControl. Two questions, Is pulse width control the same as pusle width modulatio? And two would the new RCB-3 work with these servos if they are not pulse width modulation? Thank you for any help you can give me.

  2. Hi,

    Are you saying it’s possible to drive the RCB3 with only 6 volts?
    I have a KHR-1 and i’m interested in upgrading to RCB3 without upgrading all my 6v servos.
    So please give my some info

  3. Meltdown-
    Yes, it is possible to swap out the RCB1s for a single RCB3 running at the standard KHR-1 voltage. There are several KHR-1 users here that have done it without a problem. We’re documenting the conversion and will post it as soon as we finish. Converting the motions, or creating new ones, is our biggest challenge at the moment.

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