I'm trying to build a medium sized robot that can react to commands, speak, and move it's arms, but I am having a lot of trouble figuring out the components I need. I studied the Polyro, Rooby, and a few other butlerbots, but am having trouble figuring out what parts I need to connect everything to a laptop and external power supply and have it work. I also would like to find an alternative to the AX-12 the Polyro uses, what do you guys use?
edit: So people don't have to go through a bunch of responces:
I'm planning on building a 2ft robot, similar size to aformentioned robots.
I already built several small robots, and rebuilt them.
I'm trying to step up from the little guys, and building an upper body to start, and moving towards the legs after I figure out the top.
Get a couple of cheap 360deg servos from ebay, Pololu or the like and an micro controller like an Arduino. Use one of the many start here bots as a template and get a feel for what it takes and learn from it. In no time you will be on to bigger and better bots.
The start here robot was really fun to work with, and I had a lot of fun upgrading it with my own chassis. Blender works really well if you use European measurements. I’ve made a couple small robots already, and rebuilt at least two a couple times. I wanted to study and start working on larger machines. Hope this helps and clears things up a bit.
The size of the servos for your arms really depends on
the the mass each servo will need to move. Tower Hobbies says the Futaba S3003 is rated for 44 oz-in @ 4.8v and 57 oz-in @ 6v. The servo at your elbow will have to move the forearm and nothing else. Let’s say the forearm is 12 inches of 1 inch (ID) PVC tube. The page I looked at says about 1/3 lb (5 1/3 oz) for a 1 foot section. The 6v spec will move 4 3/4 oz a foot away from the center of the servo arm. Because the weight of the whole tube is just over that, I would believe the S3003 @ 6v would be sufficient. The servo will weigh about 1.3 oz. Now, you are at 6 2/3 oz at least a foot away from the shoulder servo. An S3003 will not be able to move the upper arm, the servo, and the forearm. A bit more searching suggests that either one of the TowerPro MG995 or MG996R (both metal geared) servos will easily move the mass that I laid out above. Both servos have 130 oz-in + of torque @ 4.8v.
Fair warning any standard size servo with that kind of torque will require a good deal of current. Bajdi has used those servos in his multi servo hexapod. He built a special board to supply the current he would need for them. I believe the current draw is an Amp or better per servo. Your 6-8 servos would likely want 6-8 Amps for the group, minimum.
That’s very interesting. These are really a lot cheaper that I thought they would be. 10-15$ right? That’s a fantastic price drop from the ax-12a, which is around 44$. I might look into using all the same servos to make repairs easier. After looking at Polyro, it looks like it just feeds off of the create’s battery at 14~ volts. The wiring on that thing is a little confusing. What controller and battery setup would you suggest?
The ax-12 servos are likely worth most every penny they ask for
them. They are addressable. The servos can report current draw. I’m sure they can report their position. I believe their wiring setup allows them to be easier to use as multiples.
Re: controller and battery. I am guessing you are asking about microcontroller/computer. Use whatever you feel comfortable with. However, it is likely that an RPi would require at least an extra microcontroller of some decent size to give you all the pins you would need to access other hardware. As for the battery/s, use whatever will supply enough current to move your creation for a fair amount of time. Look at what others have used.
I was asking about a motor control board, but I noticed some robots that use laptops don’t need them? Alfred doesn’t seem to use one : https://www.robotshop.com/letsmakerobots/node/37592, but I’m not sure if I’m not noticing it. Most of the robots I look at don’t seem to tell me much about how the motor systems are set up. What would be needed if I used the aformentioned servos motor control wise, or can it really be done with just using an adaptor and the computer?
