Dear Forum members,
This is my first time dealing with robotics related project, and I want to implement the Hexapod Walker project - https://www.pololu.com/docs/0J42. Despite my lack of experience,I know some programming and the Hexapod Walker project seems not too hard to start with. All that to say, that my question may seem basic. I want to make the Hexapod Walker work much longer, let say for at least an hour for exhibition purposes.
So one way that I thought of ,is if you plug it the USB of the servo controller to a computer or wall outlet as the power source, will that work?
Another solution that I thought of is, to program the robot so it will work for 5 seconds every one minute, so it will work for one hour or so without switching the battery pack. Will that be possible?
I want the robot to work actually for three hours, but If would need to change batteries 3 times during that time, or just plug it off to give it a rest, then it will be fine as well.
Dear Forum members,
Thank you for your interest in our Hexapod project. You will not be able to power servos connected to the Maestro with the USB. Instead you could connect the servo power to a DC barrel jack. Then you could power the servos with a wall adapter.
You can also program the Maestro so that the servos are only powered for short intervals by enabling or disabling the servos. Once you get basic code for your hexapod working, the Maestro User’s Guide will be helpful for figuring out how to do that.
A third option is to scale up the battery so that you can power your hexapod longer. The battery pack we recommend for that project has been discontinued. The nearest alternative that we offer is a 2/3-AAA cell pack, but you might also consider using a 2s Li-Po battery with a 5V regulator. Since you are new to robotics, this blog post might be helpful for learning about batteries and how choose one for your project.
Thank you for your elaborated answer.
I have a few question regarding your reply:
- What kind of wall adapter should I buy to this project? how much V and is there anything else I need to know about before purchasing this item?
- Do you have any approximation of the running time of the robot using the 2s lipo battery?
And “The masestro User’s Guide” and “this blog post” links you wrote does not seem to work for some reason.
Many thanks again
Sorry about the link not working. I fixed the blog post link it in my original post and have added it again here.
To answer both of your questions, you need to think about how much electrical current your system will draw. The biggest factor in your system will be the servos. As a simple example, if your servos have a 1 A stall current, then you will want a wall adapter that has at least a 2 A output (since your hexapod has two servos). The servos are not going to draw their stall current all the time, but you want your power supply to be able to handle current spikes when the system powers on and when the motors change directions.
If you use a battery, then you can divide your battery’s capacity (reported in amp-hours) by the average current draw you expect. You could measure your system’s current draw using a multimeter set in current mode in series with the multimeter probes in series with your power supply. So if you measure that your powered system draws 500 mA on average, then a battery with a 4 Ah capacity will be able to power the system for 8 hours.
I managed to build the Simple Hexapod Walker using a DC Barrel Jack, and also program it to work with breaks, thank for your helpful guidance!
Now I want to add another feature to the robot: I want to add a servo engine that will be powerful enough to push objects, ball objects in the weight of 20 gram or similar.
So which servo should I buy that could be powerful enough to do this action, could do 360 degrees spin and could be connected properly to the maestro without or with an additional power source?
If you need the servo to move 360°, then you should probably consider one of our continuous rotation servos. Any of these could be controlled by the Maestro, but keep in mind that since these are continuous rotation servos the control commands will direct the servo’s velocity, not position. Since the objects you want to push are only 20 grams, you will probably be fine using one of the micro servos. This blog post might be helpful if you want to learn more about how you can evaluate these types forces and torques.
Thank you for your answer.
I thought it through, and I could actually use a servo engine, that does not need 360 degrees spin. Is there any more powerful servo engine that is recommended and will work with this project ? I tried using the small one and it actually worked, but I think I’ll need something that can push heavier weights.
You can use the specifications table at the top of this web page to review specifications for all of the servos we carry and look for which servos have more torque than what you are currently using. The physical dimensions are also listed, which can be useful to help narrow down similarly-sized servos. Specifically, if you are using the generic 3.7g sub-micro servo that the Simple Hexapod Walker guide recommends, this servo should be able to provide twice as much torque for the same form factor.