I just received my new Vex Signal Splitters last night and installed one in an existing robot. The robot has two motors (ch1+2) driving tank treads, and two servos (ch3+4) driving a camera tilt/pan assembly.
When using the signal splitter, I am having trouble with lots of “jitter” on the servos. I tried adjusting the trim on the transmitter and I can sometimes get the jitter to stop for a few seconds, but it always returns.
Both the Tx & Rx batteries were freshly charged, and the RF link seemed stable (the robot drives with no problems). When the remote is switched off, the jitter immediately stops, so it only seems to happen while a valid carrier is being received.
The tilt/pan mechanism works perfectly when driven by a Vex Micro Controller module; the servos hold steady if the joystick on the remote is held steady.
I will run several more experiments tonight (switching out all the parts to isolate the problem) but I wanted to ask here if this is expected behavior?
OK, I’ve retried this now with:
[LIST]
*] 2 Different Transmitters
*] 2 Different Signal Splitters
*] 3 Different VEX Servos, and 1 Hitec HS-55
*] 2 Different Batteries
[/LIST]
I plugged the Signal Splitter directly into the transmitter to eliminate the RF link as a variable.
In all cases, channels 1-4 exhibited significant jitter everywhere except at the servo travel limits. I was able to sometimes trim out the jitter, but it always came back within 30s or any time I moved the stick. Sometimes it was very regular like a 1Hz heartbeat and other times it was more random.
The interesting thing is that Channels 5 & 6 were rock solid. They did not present any jitter at all. I wouldn’t have expected them to jitter at the travel limits, but in the center I would have expected to see some jitter.
If I use a Micro Controller, there is no jitter on any channel or at any point of travel.
So, I have to conclude that the signal splitter PWM is less stable than the Micro Controller. This seems to matter very little with motors, but it makes servos jitter and vibrate in a way that makes them unsuitable for any mechanism that requires a steady hand (like a camera tilt/pan mechanism).
If this is expected behavior, then you need to update the Signal Splitter documentation to make this limitation clear. (I bought these expecting the PWM performance to match the Micro Controller.) If this is not expected behavior, then please work with me to figure it out.
Has anyone found out how to stop the jitter in the splitter?
It seems to do it real bad on the servos, But not hardly at all on the motors.
I wonder if it’s connected to a motor controller for larger motor, If it will jitter also.
Calvin
**There is nothing that the User can do to improve jitter. We are working to develop a replacement unit. We will let you know when replacements are available.
For now the Signal Splitter web page has been changed to show that with the current unit, Servos can only be used on Outputs 5 and 6.**
I could not add this to the previous thread, But If Vex is working on a replacement splitter will they post a thread on how to get this splitter replaced by Vex?
Also I no longer have the package it came in, Will this be a problem?
I need all channels to be free of jitters or the splitter is no good for me.
I’m glad to see they stand behind they’re product.
Calvin
Yes, we will make an announcement on how to get a replacement. You will not need your original package to get a replacement. Jitter will not be a problem on any Output on the “New and Improved” Signal Splitter.