My Nybble is working after carefully following all the instructions and watching the assembly videos. It's just that it seems that my cat has a bit of a shake as he is walking and performing behaviours some of the servos seem to stutter a bit causing his movements to be shakey. I am using the recommended 14500 3.7v 800mAh batteries.
I have tried the following with limited or no success:-
1. Dialing up the power a bit from the nyboards potentiometer
2. Tried Adding a 220 / 1000 / 2200 micro Farad capacitor accross the power connectors.
3. Added ferite rings arround sevo leads
If any one has had a similar problem or sugestions for a working solution please let me know.
Absolutly love this project, thanks Rongzhong!
Great discussion on an important topic. Just wanted to cross-link to a comment that @Rongzhong Li posted here about how Tower Pro servos (in the original Nybble that I have) are commonly cloned and counterfeited so it is difficult to get genuine Tower Pro servo.
Hi all, I with purchase I received some servos that are not marked with any brand, in plastic casing and I am considering replacing them and servo arms as well. Namely after 3 min. Kitty legs are unscrewed and I have to mount them again. I wanted to replace servo arms with alu that are stronger and hold much better. I have some quesitons for you:
Did anyone tried this and is it really helping?
Did anyone mounted better servos such as Savos or similar?
For Alu arm how many tooth have your recommended servos that is which servo spline is used? I think you said somewhere 25 teeth which should be then B1 mini spline. - is that correct?
Thank you, I will try this and get back to you.
You were right my PWM ranges were initialy wrong I got them from some documentation on a site that sells the servo. But I don't trust them to be correct. It says they use standard PWM range. The Sketch program via the Arduino UNO works well and the servos moved, and responded to the inputs. After following the text prompts from the serial window, The program reported these PWM ranges for the 2 servos. As in my above post.
I'm still not there, I think I have the PWM ranges correct NOW, but the Nybble moves so SLOWLY and the movements are REDUCED in there range. For example in the WAVE or HI behavior. I can see Nybble attempting to wave and his left paw moves up and down but the shoulder position is not moving far enough, and the paw is not moving up and down enough. it just wiggles up and down a small amount.
It looks like I need to increase the range of movement and speed up the movement.
Can I increase the amount of movement per position say in 6 degree increments instead of 5 degree? I'm not sure how to achieve this.
I used the Sketch code you provided with my Arduino UNO to get the PWM ranges of the two servos:
Shouldder servos K-Power DMC809 = 283 - 2080 replaces MG92B
Knee Servos Power-HD HD-1810MG = 490 - 3100 replaces MG90D
Uploaded modified sketch code to cat.
Cat performs all behaviors VERY SLOWLY and with LIMITED RANGE OF MOTION
Should I change the constant in the code ?
#define MG92B_RANGE 150 to #define MG92B_RANGE 180
#define MG90D_RANGE 150 to #define MG90D_RANGE 180
Is there a way to speed up the servo movement? at the moment it is very slow?