Components:
SparkFun Servo Trigger WIG-13118 https://www.sparkfun.com/products/13118
Servo - Hitec HS-805BB (Giant Scale) ROB-11881 https://www.sparkfun.com/products/11881
The components are working as expected, but the servo jitters around the commanded position. This is happening at both position A and B regardless of the position and timing set. The servo moves slightly back or forth every few seconds rather than simply holding position.
Any way to eliminate the Jitter? Is this servo not compatible? Any help appreciated!
Hi Owen,
As far as I can tell, there should be no issue with using that servo with the SparkFun Servo Trigger. An initial guess would be that it is possible the pulse duration being sent by the Servo Trigger is outside of the range of the HS-805BB but according to the specifications of the servo and the servo trigger, that should not be an issue. The only other thing I could think of would be a power issue. Make sure your power source can supply at least 700mA at 5V if you have no load on the servo. You will most likely need 1A or more if you have a load attached to the servo.
To make sure there is no issue with the pulse duration, I am going to test this servo with our Servo Trigger and I will get back to you with those results. Another test you could do (assuming you have the parts to do it) would be to connect the servo to a microcontroller like an Arduino and test it with some code like this [example code from our Hobby Servo Tutorial. That way you can identify if the issue is with the servo itself or something else. One note, you’ll need to power the HS-805BB from either the Vin pin on your Arduino if it is between 4.8-6V or a direct power supply since the 5V pin on an Arduino can realistically only supply about 500mA.
I hope these suggestions help and I will follow up on this post after I have gotten a chance to test the Servo Trigger with the HS-805BB.](Hobby Servo Tutorial - SparkFun Learn)
A quick update:
I tested the Servo Trigger with a brand new HS-805BB and it works without issue. I was able to get smooth motion from A to B regardless of the start/stop position or travel time. One thing I did notice is I was able to possibly recreate your issue with it not holding a stable position. Initially, I was using some stranded wire soldered to the IN and GND pins for the input and touching those together. It worked okay but was not creating a solid connection so sometimes it would “jitter” because the connection was not sufficient. I switched to using some solid core wire to get a better connection and that resolved the issue.
I would recommend checking that your connection for the input is soldered well and is making a good connection when closed. That will most likely resolve the issue but if not, please reply to this post and we can continue troubleshooting.
Update: Thanks for the feedback. Ultimately I was able to trace the issue back to a noisy power supply (there was zero jitter when powered from a battery). On the advice of my electrical engineer father in law, I added a capacitor between GND and VCC on the power cable and was able to fix the issue. With a 470uF capacitor, jitter is now completely eliminated. One other note, I am using a high voltage signal as the trigger after soldering SJ2.
Hey again Owen,
Thanks for the update and that’s a great idea from your father in law regarding the filter/debouncing capacitor for the power supply. I’m glad to hear everything is up and running properly now.
Wow! This fixed my issues with the board as well. Even though I was using the recommenced power supply from Sparkfun, I was seeing jittering like crazy. Now I’m working on running 4 of these boards from the power supply. Can anyone help me determine if I need to put just one capacitor across the power supply before splitting and routing power to each board? Or do I need a separate capacitor for each board? If just one, do I need to switch to a bigger capacitor?
Thanks again, I’ve spent 3 weeks trying to get this board to work and this is the first promising result!