Thanks to everyone for their input on this topic. I hope the discussion won't end here as there is still more to be discovered. I am particularily interested in trying DJ's proposal to run a Sabertooth/Kangaroo combination as a servo! My parts won't be here for few days so if anyone has them laying around and can make this work I would like to hear about it!

Castle

Woo-hoo i win this round!

@Castle, if you do run into challenges using it in r/c mode, consult the manual and if that doesn't help, contact dimension engineering - i hear they have a great support line.

@DJ, Thanks for the help. I have read in some strange places around the forum cautioning about using R/C mode but I can't remember where. Is there something different about R/C servos? Can a large high power R/C servo be used by EZ-B? Is there anything different that I need to know to use one or different controls or settings in ARC or are all servos basically the same?

You can find out how a servo works here: https://synthiam.com/Tutorials/Lesson/48

There is a LEARN section on the top link of the website. You will choose your ez-robot product and learn information about it. That's a great place to start.

As for how a servo works regarding the "power" is irrelevant. This is because a servo is nothing more than a motor with a measurement that tells what position it is in. And a circuit runs to keep the motor in that position. The measurement is usually taken with a potentiometer, as i have mentioned.

The signal that tells the motor to move is not powered by the ez-b. The ez-b is only transmitting a 3.3v signal. This signal tells the kangaroo or servo what position to hold. This signal does not power the motor. The motor, in your case, will get it's power from the battery directly.

There is a datasheet regarding the EZ-B, like all electronics. And in that datasheet defines the max current it will provide - obviously not enough to power a motor. However, signalling a controller to move a motor is a different story - which is what the purpose of an HBridge is.

There is absolutely no reason why any servo ever made will not work with an EZ-B, unless it is engineered incorrectly or not following servo specs. Dimension Engineering is a great reputable company and i am certain their product works as described. Any situations from past user experiences would be due to mis-understanding the documentation. If that is the case, contact Dimension Engineering customer support.

Again, contact dimension engineering customer support for questions about using their product. EZ-Robot has absolutely no additional detail about Dimension Engineering products outside of what is presented in datasheets and product sheets.

@DJ, Wonderful news! Thank you for the clarification on servos - I need to source a high power servo, probably from an R/C off road car for part of my robot so it is good to know that I don't have to be looking for some particular kind of servo!

I hate to be a wet blanket here but.. I put a lot of time and effort trying to get the EZB to work with the Roo in RC mode. I couldn't get my motor to respond as like a servo or even move in a reliable manner or even at all most of the time. It could very well it was as DJ says and I was misunderstanding the documentation. The thing is there is very little documentation on this function. It really didn't seem to hard though I set the dip switches on the Roo and attached it to a digital port on the EZB. I then sent it regular servo commands from ARC. For example:

Servo(D1, 98)

I would like to give it a try again now that I have more experience with both ARC and the Kangaroo. I was pretty green back then. One thing I'd like to try to get it to work is to set the ServoSpeed() at different times t see if it would make any difference. To this day I still have problems getting regular servos to move because I've set the servospeed() at the wrong time.

One other thing that should be brought up. If you are able to get the Sabertooth/Kangaroo to operate in RC mode and attach it to a digital port you'll be setting it up like a regular servo. You will not be able to get feedback from the Roo. It will operate like a regular blind servo. If set up to use a microcontroller you will be sending simple serial commands through the Uart ports. This will allow you to receive speed and position info back from the Roo.

Thanks Dave / lots of insight for me to capitalize on / my problem is that I think I know what I want my robot to do / it is about figuring out the most elegant way to do it - and there are a lot of gaps in my knowledge base that I don't know what I don't know / For example / if I have he servo move to 98 and the Roo does it / why do I care about the value being reported back to the controller? Because the next position I want the robot to move to is just another set of coordinates that when fed to the Roo would be executed... So I have a lot to learn and discover ...Update - my Roos should arrive on Friday so I may be playing earlier than I thought / then I will probably have lots more questions

you got it castle - ARC doesn't care about the position from the servo because it tells the servo what to do.

As for dave's experience and others... this is why i have repetitively mentioned "contact dimension engineering customer support" - because no one has done that. We seem to be acting for their support line I know i have most of the answers but for this one, I can only quote the documentation and product information. They made the product and will have the answers you seek