Clearly I haven't installed any holding brakes on the servos. After I filmed this, I tested the holding, and a Hitec 645MG in the elbow caught fire. I switched off the microcontroller and the arm crashed down towards the centre of the Earth. After I replaced it, my friend wanted to see, so I turned it back on and it smashed him in the face.
I have finally figured out how to rig a spring against an electromagnet that activates when there is a pulse to any given servo, so this will eventually result in perfectly amateur holding brakes (another shipment of copper wire reels is on it's way), but I just hoped that there was a servo like the Torxis i00600 that was a lot smaller and simply didn't move without being powered.
I was told that car windows use stepper motors, so even now, after watching many videos of their operation, I keep wondering if all stepper motors are like that: able to hold their position against my arm pressing down hard when I drive. The semi-circular toothed mechanism pressing against the stepper cog doesn't seem like it would do anything to lock it, so either steppers are all internally self locking, there are extra gears inside car window steppers to create a lot of resistance, or there is a holding brake on all car power window motors.
I would definitely like to see any examples of full scale humanoids people have built, especially how they have solved the holding problem. If its worm drives, then I'd be keen to see the dancing speed and hear the volume of the motors together.
To answer your question from the other duplicate thread which has been deleted, you can connect 99 Dynamixels to the EZ-B v4 + 22 PWM Servos.
The power providing through the EZ-B v4 will be limited. However, the number of servos for your custom application will determine how many servos based on current load. The EZ-B v4 datasheet defines the current capacity.
By their nature (internal magnetic cogs, held in place by electromagnetic coils) Stepper motors do not have any holding power without applied power, unless they are geared. In my experience, true geared stepper motors are rare usually you see steppers with a worm gear drive attached. The major problem with steppers, when it comes to robotics, is that they don't have any positional feedback built-in like servos do. You have to add your own in the form of a potentiometer, break-beam encoder, or a limit switch.
Window motors from vehicles are usually DC gear motors, but standards may have changed over the years. I'd like to see if newer vehicles have geared steppers installed instead.
Thanks for the current load reference, DJ, but I never risk my microcontrollers by running the servo power through them. I always use at least a 46 amp power supply and only use the microcontoller power for the pulse lines.
Jeremie, thanks for letting me know that the stepper motors in car windows contain hidden worm drives. That's what Richard R said but I didn't believe him. Sorry Richard. It makes sense, though. They're extremely slow and they sound like worm drives.
I want my robot to be able to dance and do karate at least as well as a human (I'm going to attach him to a wall, floor or ceiling so he won't be doing any running or back flips except on the spot), so there's no way I'll be using worm drives.
Dynamixel series linking seems like nothing more than a neat wiring solution as far as I can see, but they do include position memory wiring in 40 kg.cm+ servos. Even so, they are annoyingly rectangular with an off-centre shaft like every other hobby servo, so I still need to design and manufacture robust housing to correct this major design setback. And the price of dynamixels is higher than some round flange, center-shaft industrial level servos, so I would need to weigh it up. Hopefully I won't need to weigh up anything because after literally thousands of hours of searching the ENTIRE internet (it seems), there will be an existing product that just makes sense.
@Zxen, I'm using both a car window motor and a windshield wiper motor in my robot arm. The both are simple DC motors (not stepper motors), have worm gears and and are nearly silent. They can be found in many torque strengths and speeds. Most are great for holding position with no power (I did however find one once that did not). Visit the Robot Marketplace for a wide choice of motors.
The Robot Marketplace
As mentioned you'll have to find a way to attach a pot or encoder for feedback to get speed and position control and a motor controller like a Sabertooth with a Kangaroo X2 attached.
Here's a video I made of the Car Window worm gear motor running my arm carriage system:
Here's another video where I used a windshield Wiper worm gear motor used for the elbow of my arm:
I have seen inmoov, which is impressive. But I prefer my shoulders to be more basic like this: https://www.youtube.com/watch?v=aUPDsbbNUjM
Clearly I haven't installed any holding brakes on the servos. After I filmed this, I tested the holding, and a Hitec 645MG in the elbow caught fire. I switched off the microcontroller and the arm crashed down towards the centre of the Earth. After I replaced it, my friend wanted to see, so I turned it back on and it smashed him in the face.
I have finally figured out how to rig a spring against an electromagnet that activates when there is a pulse to any given servo, so this will eventually result in perfectly amateur holding brakes (another shipment of copper wire reels is on it's way), but I just hoped that there was a servo like the Torxis i00600 that was a lot smaller and simply didn't move without being powered.
I was told that car windows use stepper motors, so even now, after watching many videos of their operation, I keep wondering if all stepper motors are like that: able to hold their position against my arm pressing down hard when I drive. The semi-circular toothed mechanism pressing against the stepper cog doesn't seem like it would do anything to lock it, so either steppers are all internally self locking, there are extra gears inside car window steppers to create a lot of resistance, or there is a holding brake on all car power window motors.
I would definitely like to see any examples of full scale humanoids people have built, especially how they have solved the holding problem. If its worm drives, then I'd be keen to see the dancing speed and hear the volume of the motors together.
To answer your question from the other duplicate thread which has been deleted, you can connect 99 Dynamixels to the EZ-B v4 + 22 PWM Servos.
The power providing through the EZ-B v4 will be limited. However, the number of servos for your custom application will determine how many servos based on current load. The EZ-B v4 datasheet defines the current capacity.
By their nature (internal magnetic cogs, held in place by electromagnetic coils) Stepper motors do not have any holding power without applied power, unless they are geared. In my experience, true geared stepper motors are rare usually you see steppers with a worm gear drive attached. The major problem with steppers, when it comes to robotics, is that they don't have any positional feedback built-in like servos do. You have to add your own in the form of a potentiometer, break-beam encoder, or a limit switch.
Window motors from vehicles are usually DC gear motors, but standards may have changed over the years. I'd like to see if newer vehicles have geared steppers installed instead.
Thanks for the current load reference, DJ, but I never risk my microcontrollers by running the servo power through them. I always use at least a 46 amp power supply and only use the microcontoller power for the pulse lines.
Here is a link I found to how industrial servo holding brakes are set up, but I still need to find smaller and cheaper ones: http://www.applied-motion.com/news/2012/07/did-you-know-holding-brakes-step-motors
Jeremie, thanks for letting me know that the stepper motors in car windows contain hidden worm drives. That's what Richard R said but I didn't believe him. Sorry Richard. It makes sense, though. They're extremely slow and they sound like worm drives.
I want my robot to be able to dance and do karate at least as well as a human (I'm going to attach him to a wall, floor or ceiling so he won't be doing any running or back flips except on the spot), so there's no way I'll be using worm drives.
Dynamixel series linking seems like nothing more than a neat wiring solution as far as I can see, but they do include position memory wiring in 40 kg.cm+ servos. Even so, they are annoyingly rectangular with an off-centre shaft like every other hobby servo, so I still need to design and manufacture robust housing to correct this major design setback. And the price of dynamixels is higher than some round flange, center-shaft industrial level servos, so I would need to weigh it up. Hopefully I won't need to weigh up anything because after literally thousands of hours of searching the ENTIRE internet (it seems), there will be an existing product that just makes sense.
@Zxen, I'm using both a car window motor and a windshield wiper motor in my robot arm. The both are simple DC motors (not stepper motors), have worm gears and and are nearly silent. They can be found in many torque strengths and speeds. Most are great for holding position with no power (I did however find one once that did not). Visit the Robot Marketplace for a wide choice of motors. The Robot Marketplace
As mentioned you'll have to find a way to attach a pot or encoder for feedback to get speed and position control and a motor controller like a Sabertooth with a Kangaroo X2 attached.
Here's a video I made of the Car Window worm gear motor running my arm carriage system:
Here's another video where I used a windshield Wiper worm gear motor used for the elbow of my arm: