-I installed all servos and have everything setup. They are lined up with all screws in the correct place. I am assuming that is correct.
-I have been running the servos with ezblock.
- I also have turned off the power and moved the legs manually so they line up with the last page on the instructions.
-what I am confused about, is it would appear that would not calibrate them correctly and this is where I need help
-I have pressed the zero button which supposedly sets the servos to be calibrated correctly if all servos were perfectly set up and I did not move the gears while the power was on or did not move the gears while the power was off, but I did.
-saying that, I am confused how to go about calibrating it when all the servos are every which way once I pressed the zero button
- so now I explained that nothing is lined up correctly.
-what I do not understand what steps do I perform so everything gets set up correctly
-if someone could give me a step by step instructions how to calibrate correctly that would be great because I am confused
The issue is most likely in the way the servo arms were installed: when installing the servos, you need to press the Zero (calibration) button first and then insert and fix the servo arm at a 90° angle. If you adjust the angle by feel while the power is off, or install the servo arm first and then press Zero, the zero position stored in the servo will no longer match the actual mechanical position, which is why all the servos appear to be out of alignment. This does not mean you have damaged the hardware, so please don’t worry.
Please redo the procedure as follows:
First, remove the servos from the servo arms.
Keep the PiCrawler powered on, press the Zero button, and let the servos return to their zero position (90°).
While it is powered on and Zero has been pressed, insert and fix the servo arm at a 90° angle.
For the detailed operation, please refer to our assembly video, at 7:23: https://www.youtube.com/watch?v=vna6QtXPGt4
You can also refer to the PiDog tutorial, which uses the same principle: https://youtu.be/zmN_mGxTKuU
One thing is especially important: any servo angle adjusted while the power is off is invalid. Only the angle set while powered on and after pressing the Zero button is a valid angle.
Please try again following these steps and then let us know the result:
After reinstalling, do the servos now return to zero and align correctly?
If any individual servo still does not move, jitters, or gets hot, please tell us which pin number it is connected to (e.g., P10), and we will help you determine whether it is the servo itself or the board pin.
We look forward to your feedback and will keep following up until the problem is solved.
Thank you for your help. Could you please verify my steps I am going to perform.
-please explain if i can or cannot move the claws if the robot power is off.
-I wrote a lot but please read it carefully. I think this is what I need to do
-I think I understand what I have to do.- I have to disconnect each of the 12 servos from each leg.
-once they are disconnected so the servos, will move but it is not connected to the claws then:
-I pressed the zero button, which lines up the servo so it set to zero so when I attach the servo back to the claws, it is positioned correctly
-once I set the servo to zero, then the gears can not be moved while connected or disconnected to power.
-if I did then the servo gears will not be allied correctly.
-I am going to explain step by step what I have to do. Please verify that would be the steps I have to do.
-what I explain I will have to repeat it 12 times
-I have to disconnect all 12 servos from the hat.
-I have to unscrew servo one from the claw so it is as if it came right out of the box. Nothing connected to it
-I then connect servo one to the hat.
-I press the zero button and the servo gears should be lined up correctly.
-I then disconnect the servo from the hat.
-after that above process is done, the only time I move the gears is by using the zero button otherwise everything will be out of wack again.
PLEASE VERIFY THAT IS TRUE.
-I then screw the servo back on to the crawler and since it only can be connected one way it should be lined up correctly, see below picture.
-I then repeat that 11 times.
-after that is done, I connect the 12 servos to the hat.
-when I press the zero button, the claws should not move because everything should be lined up.
-if I run a program and stop it in the middle, and then press the zero button everything will be lined up again looking like the below picture.
-PLEASE VERIFY IF I TURN OFF THE POWER, I CAN OR CANNOT MOVE THE CLAWS.
-I KNOW I CAN NOT MOVE THE CLAWS WHILE THE POWER IS ON
-is it true the servos are lined up correctly on the below picture
Thank you so much for taking the time to write out every step so carefully, and for being willing to double-check the procedure with us — that really helps. Let’s go through it together and clear it up.
First, let me answer the questions you care about most:
Can you move the claws when the power is off?
When the power is off, yes — you can turn the claws/gears by hand, and doing so will not damage the servo. But please note: any angle you get that way is invalid and cannot be used as the zero position. The servo’s zero position is only set correctly when the power is ON and you press the Zero button. Once you turn the gears by hand while the power is off, the zero position stored inside the servo no longer matches the actual mechanical position — and that is exactly why all your servos appear to be pointing in different directions and completely out of alignment.
One important warning: while the power is ON, do NOT turn any servo by hand, or you will damage the gears inside the servo.
The correct calibration procedure
Please calibrate each servo one by one, following these steps:
Disconnect all 12 servos from the HAT.
Remove the fixing screw between the first servo and its arm, then pull the servo off.
Connect the first servo to any PWM pin on the HAT.
Press the Zero button — the servo gear should now turn to the correct zero position.
Reinstall the servo onto the crawler robot and tighten the servo screw. If you’re unsure about the mounting position, you can refer to the assembly video from 7:23 onward: https://youtu.be/vna6QtXPGt4
Disconnect the first servo from the HAT.
Repeat the same steps for the remaining 11 servos.
When all are done, reconnect all 12 servos to the HAT.
In other words, the key is not to “adjust the angle by feel,” but to “connect one servo to a pin + power on + press Zero + reinstall at the zero position.”
Should the servos be aligned after pressing Zero?
If the servo arms were installed while the power was ON and after Zero had been pressed, then every time you press Zero afterward, the servos should return to the aligned position. If they were installed by feel while the power was off, they will not align after pressing Zero, and you’ll need to redo it using the method above.
Thank you again for your patience — we’ll keep following up until your issue is resolved.
2 things you need to understand. 1/ the servo when powered and set to zero moves the servo mechanism to its central position and no limbs must be attached. Do not power off.
2/ the splines on the servo, where the limb attaches are not precise. An attached limb will seat several degrees either side of the true angle the limb needs to be as it jumps to the nearest spline. That is the reason you have to calibrate. Calibration nudges the servo to a between spline position and records that minute difference for use in the program moving the limbs. Power on. Fit the limb as close to the desired position with the power on. Repeat for all limbs, still with the power on. Calibrate each limb in turn, still with the power on. You should notice only a slight difference in numbers around the central position. At this point, you can power of and power on again and recheck calibration. Apart from a bit of flexing, the initial calibration values should not change, or need to be changed. If limbs have play in them then the servo or fixing is substandard and you will never get it right.
I read your explanation and it makes sense to me except for one thing. This is how I think the servos work
-I unplugged all servos from the hat.
-I unscrewed all three screws from servo one. One bigger screw from the center of the servo and black arm and two tiny screws that connects the claw to the arm
-I left the black arm on the servo because with the three screws that connect the servo to the arm, the arm is not connected to the mettle claw any more.
-that means if I move the arm while the power is off, the servo gears will turn with the arm.
-I then turn on the power with servo one connected to the hat.
-then I press the zero button for servo one
-the servo gears and the arm move to the zero position.
This is where I am confused.
-what I did next is, I turned off the power, unplugged servo one.
-then while power is off and servo unplugged from hat, I manually I turned the servo one arm 1/4th clockwise which also moved the gears.
-now with the power off and the servo unplugged from the hat, the servo is not calibrated correctly any more
-BUT, once I turn on the power and plug servo one into the hat and press the zero button, the arm and the gears move back 1/4th counter clockwise.
-once that happens servo one is then calibrated correctly again
IS THAT TRUE?
-what this tells me, if the above is true, as long as the power is off and I move the arm and gears (to be able to put the two tiny screws back on that connects the arm and the metal
claw) at that point the claw and the servo are not calibrated any more.
-BUT, once I turn the power back on, and plug servo one back onto the hat, I then press the zero button servo one and the claw is now calibrated again.
-if everything I say is true, the servo has a memory and once it gets power again and I press the zero button it will go back to the calibrated position again.
-final conclusion is, while power is off,and the pi crawler is completly assembled again, I can move the claws any way I want, because
-ONCE I TURN THE POWER BACK ON AND PRESS THE ZERO BUTTON, THE PICRAWLER AND SERVOS WILL ALL BE CALIBRATED AGAIN BECAUSE EACH SERVO GOES BACK TO THE CORRECT POSITION BECAUSE THE SERVO AND CLAWS WERE MANUALLY MOVED ONLY WHILE THE POWER WAS OFF
IS THE ABOVE STATEMINT TRUE?
-is any of what I said not true
I know I am very detailed, because I was in I.T. for over 40 years before I retired 10 years ago, if you think this will confuse people on the forum rather than help, you may want to delete this discussion from the forum.
Thank you dlorfel
Actually, you only need to unscrew the fixing screw between the rocker arm and the servo. The other 2 screws used to fix the servo to the structural part do not need to be removed. Please refer to this PiDog repair video: https://youtu.be/zmN_mGxTKuU
Since you have already disassembled it almost completely, I suggest you carefully watch the assembly video we provided again.
I’m not sure why you always want to turn the servo when the power is off. I said before that turning it when the power is off is invalid — as soon as it is powered on, it will return to its original position. Please give up the idea of turning the servo by hand. Just think of the servo as something that cannot be turned by hand — you can only, while powered on, insert the servo shaft into the rocker arm according to the corresponding angle, and then fix it with the servo screw.
