Hi,
We are going to be running the Orbit Odyssey camp and are prepping our hardware for it. We have been playing around with some designs posted to Printables and in particular the “forklift”. While doing that we have run into one potential issue and a question.
Issue: the block code appears to only support rotating the servo to a specific angle. I don’t think the amount of total degrees of travel is going to be enough to be able to make the forklift go all the way up. Is there a way, assuming we have a servo that supports continuous rotation, to drive the serve continuously?
Question: are there any limitations on the sizes of servos we can use? The kit comes with a sub-micro servo and I am wondering if there is any reason we cannot use a standard servo such as the one that Rev robotics sells (REV-41-1097).
Thanks, in advance, for you help!
update - I did a little searching for a possible motor that could be used on the XRP other than the ones that come with the kit instead of trying to use a continuous servo. Sparkfun has these motors and the description indicates that they work with XRPs. Has anyone tried them and if so how well do they work? N20 Motor With Encoder and Cable (Pair) - SparkFun Electronics
@SparkFro or @jrw4561 can you answer this?
@SparkFro It might be good if we created a table that showed the parameters to look at when selecting a servo.
@schindm
About continuous servos, there are a few different ways they are controlled. Some interpret a 90 degree signal as stop, and 0/180 degree signal means full forward/reverse. These would work with XRP.
All standard hobby servos that use PPM signals should work with XRP, the only limit may be that if the servo is too big, it is going to draw too much current and brown out the robot.
Those N20 motors are designed to work with XRP, they are a really cool motor choice, I recommend them.
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Hi there! Sorry, was on vacation last week.
Is there a way, assuming we have a servo that supports continuous rotation, to drive the serve continuously?
Yes! All servos with a 3-pin header use the exact same electrical PWM signal to command the servo. Doesn’t matter if it’s a standard servo, continuous rotation, or even ESC motor controllers; they all use the same PWM signal. The provided servo blocks are intended for use with standard rotation servos, but it will still generate the a PWM signal that can be used by other devices.
Question: are there any limitations on the sizes of servos we can use?
The main limitation is power. Most servos operate on a range of 4.8V to 6V, and different servos will draw different amounts of current depending on their size (and what they’re actually doing). The servo headers on the XRP Control Board provide 5V, so any servo that accepts 5V power should work fine. The single 5V regulator on the board can supply up to about 3A total, assuming your batteries can provide that much current as well.
I am wondering if there is any reason we cannot use a standard servo such as the one that Rev robotics sells (REV-41-1097).
I’ve not tested that specific servo myself, but the product page lists a 4.8V minimum, so I assume it would work fine!
Sparkfun has these motors and the description indicates that they work with XRPs. Has anyone tried them and if so how well do they work? https://www.sparkfun.com/n20-motor-with-encoder-and-cable-pair.html
They’re wonderful! This project made by @jrw4561 makes use of them: NanoXRP (half scale XRP Robot) by Experiential | Download free STL model | Printables.com