With your hexapod setup, what battery life were you seeing?
I generally don’t worry about battery life (on this particular robot). I have a 2S 5Ah LiPo pack and it has always lasted as long as I’ve needed it. I generally don’t run the robot for more than 15 minutes at a time and the 5Ah pack can easily last that long. If I were to take a wild guess, I’d say the battery pack would last an hour is the robot were very active. Under normal use with the robot walking a bit and the stopping to “look around” (it presently doesn’t have any sensors), I think the battery would likely last a few hours.
I always use a LiPo meter/alarm with my battery packs so if a cell starts to get too low, the alarm will warn me before the battery gets damaged.
I purchased several 2S 2.2Ah packs I plan to use with the hexapod. I think 2.2Ah is enough for occasions when I want to use the robot, and the smaller pack will be easier fit inside the frame.
How well did your servos work and how much current did each draw during actuation? Is there anything you would have done differently in that area?
I haven’t measured the current draw. While each servo is capable of drawing over an amp of current, I don’t think (on average) the whole robot draws much more than the a few (3?) amps in most situations. While the average current demand isn’t extremely high, servos draw current in huge spikes. The big regulators and large battery supply are required to deal with these current surges.
I’ve only measured the current with the robot powered from my bench supply. While on the bench the robot is supported on a box. I could be way off on my estimate about how much current the robot draws. I should measure the current under load. I have the gadgets to measure the current, I just haven’t taken the time to make these measurements.
The main thing I’d perhaps do differently would be to research the voltage regulator options in more detail. I’m not thrilled with the two giant regulators I’m using. There are likely more compact solutions. The regulators I’m using work fine so I don’t feel much pressure to find an alternate solution.
One thing worth mentioning is the possibility of using servos capable to connecting to a 2S LiPo pack. I was told the servos I used should be safe when used with a 2S LiPo and the servos didn’t burn out when powered this way but the servos jittered severely at the higher voltage. I’ve had a few small servos emit their smoke when powered from a 2S LiPo. I think the only servos I have which work okay on a 2S LiPo are the CR high speed servos I purchased from Parallax.
If you can use servos capable of being powered from a 2S LiPo, you’ll save yourself a lot of trouble having to deal with voltage regulators.
How would you describe the Parallax community?
Extremely friendly and helpful.
The more I read about this, the more I feel inclined to perhaps start with a hexapod as it seems to have significant documentation in the community, and is somewhat more straightforward than my my project goal (the scope of which is perhaps too ambitious for a first project).
I guess I don’t understand what you wanted to accomplish with your original plan. IMO a robot arm is a bit easier to manage than a hexapod. I don’t know how you planned to use the six arms but a robot arm is (generally) stationary so you don’t need to carry around your power supply. Power supply issues are a big challenge when dealing with lots of servos.
One aspect of a robot arm project which is harder than most people realize is how much torque is required to support an arm of any significant length. I have one of Crustcrawler’s “Smartarms” which uses a bunch of Dynamixel AX-12+ servos. If I’m careful with how I manipulate the arm, I can sometimes manage to pick up a soda can. I can’t do this consistently but if the can isn’t too far out of alignment with the arm’s claw, I can get the arm to pick up the can. The can needs to be EMPTY to do this. A full can of soda would be much too heavy for this sort of arm. I should add I used the original claw. A claw with a different shape would likely have an easier time lifting a can but I’d be surprised if the arm could pick up and pour a full can of soda.
A robot arm capable of doing real work would likely be expensive to build. You’d need more than just hobby servos to power it.
I’m not sure what you mean by “significant documentation” when it comes to hexapods. I’ve documented the mechanical aspect of my hexapod pretty well but I haven’t posted the code for my hexapod. I’m pretty sure there is Arduino hexapod code available but I don’t know where it is.
I was just looking at the Stubby code on GitHub and don’t see any indication it uses the Arduino bootloader.
I believe Bajdi published his code (I’m not sure about this) but it had likely been published on Let’s Make Robots which has since been purchased by the (IMO) evil corporation. Badji didn’t accept the new terms of service (aka selling one’s soul to the devil) so all his posts were deleted from the site (all my posts were also deleted). So I don’t know where Badji’s hexapod code is. I’m sure there are other sources for hexapod code but I’m not sure if I’d call this “significant documentation” (though I’m not saying it’s wrong to do so).
I think the Stubby code would likely be a good place to start if you wanted to make an AVR based hexapod.
While I think I did a good job programming my hexapod (I wrote the code myself), I think Stubby out performs my hexapod in several respects. I haven’t added the ability to have my hexapod tilt and twist the way Stubby can.
TL;DR - A hexapod is a good robot project but it’s far from easy.