Conductivity between input pins

Support Servo controllers and servos
1

Hello,

I’m working on a robot project for my university. Therefor I’m using Pololus ‘mini maestro 12’ to control some servos.
I use the script modus to run a self-written program. The programm should read two input pins and drive two servos. This works fine exept from one little (big) problem:

I have a strange conductivity between the input pins. When I connect one pin to 5V I get nearly the same voltage on the other input pin, too. But I can’t measure a resistance with a meter. I also tried it with different input pins with the exact same result.
When i use the ‘Step Script’-modus i read ‘1023’ on the pin that is connected with the power source and around
’1000’ (but not allways the same value which makes it difficult to define a threshold) on the other pin that is not connected. That means for the program that one times the ‘right’ pin detects a HIGH and another times the ‘wrong’ pin is seen as HIGH from my program.
At the moment I connected the power directly to the input pins without a pull-up- or pull-down-resistor. But i also tried it with resistors with the following result: Everything works fine in the ‘Step Script’-modus. I have 1023 on the connected pin and 0 on the not connected. The program is doing the right things. But when ich switch on the ‘Run Script’-modus, nothing happens. Either the connected pin nor the not connected one will be seen as HIGH from the program.

I’m working on this problem for hours and hours now but couldn’t fine an solution. I really need some help because the robot has to run next week.
I’m looking forward for an answer and a big thanks in advance.
Greeting from Germany
Michael

2

Hello, Michael.

If you leave an input pin floating, with no outputs or pull-up or pull-down resistors connected to it, then it is normal for its voltage to be affected by the voltage on nearby pins.

I’m sorry you are having trouble with your Maestro script. Please simplify your program to the simplest thing that should work but doesn’t. Then please post here:

  1. The entire source code of your Maestro script.
  2. The inputs (what are you doing to the input lines?)
  3. The expected behavior of the Maestro
  4. The actual behavior of the Maestro.

–David

3

Hello David,
Thanks for the advice with the resistors! I use pull-downs on the input pins now.

The problem was with the input pins and the AD-converters. After a lot of testing I put a delay of 500ms before the ‘get_position’-command. And now it looks like its working. Seems like I polled the AD-values to fast. I programmed a loop where i polled the values all the time without a delay.

Have you ever heart about this problem before?
Michael

4

There should be no problem with polling the values fast, but you might want to add a delay at the beginning of your program to make sure the Maestro has had time to read the inputs for the first time.

–David

5

Ok, thanks for your help.

Michael