Controling the On time of a metro object (toggeling 0 1)

I can't help you with the Arduino part but the timing is easy enough:

Thanks but it is doing the opposite . I need that the on time will be 20ms and the off time will be 230ms

EDIT:
ok - if I change the delay time when the metro is active it will flip the operation. How can I avoid that?

post some details about timing of motors.
Are they all independent or follow some
fixed timing ?

To be most flexible, you should address each motor
with some ID prepended, and use that ID in Arduino to address
specific motor output.

Then ... using delays might look ok, but you want to have
definite ON or OFF state.
using delays to toggle is not optimal way.

post some details about timing of motors.
Are they all independent or follow some
fixed timing ?

the timing of motor is unknown - I would like to just build the surface in max to control X amount of solenoids (just for practicing the method of sending multiple data from Max to Arduino) - so it might be that a metro will be constant every 500ms and the other every 1 sec and the other two will pulse each random interval. What I do know is that the ON time for each pulse interval should be around 20ms to 40ms and the rest of the interval should be OFF.

To be most flexible, you should address each motor
with some ID prepended,

Is it how I should do it in Max?

and use that ID in Arduino to address
specific motor output.

This is the difficult part. how can I take all the data I'm sending through Serial in Max and read that in Arduino and translate each solenoid 0 1 state to the gpio outputs?

Then ... using delays might look ok, but you want to have definite ON or OFF state. using delays to toggle is not optimal way.

What do you mean? How would you do it without delay?

I'm getting those errors when trying to send the string from max to arduino via the serial in the above patch:

About your metro question:

About the error message you get using [serial]: of course, [serial] doesn't understand the message solenoid2. I would recommend spending some quality time with some of the Arduino Communication tutorials, for instance these ones that communicate with Max:
- https://docs.arduino.cc/built-in-examples/communication/Dimmer
- https://docs.arduino.cc/built-in-examples/communication/VirtualColorMixer
(Max code is included in the tutorials)

Thanks for your metro patch.
While the dimmer tutorial is great - they show only how to pass 1 sequence of numbers from Max to Arduino.
What happen if I want to pass few of those numbers using multiple slides in max? (to dim multiple leds for examples)
how can I separate each of those values and control different leds using arduino?

here is the max patch from the dimmer example:

Now, if that's clear, then you can do what Source Audio suggested above: send from Max to Arduino a formatted message with a different ID for each motor. For instance, you could decide that 65 is for motor 1, 66 for motor 2, etc. If you send just a 0 or a 1 to the motors, what you send from Max would look like:
65 1 (turn on motor 1)
65 0 (turn off motor 1)
67 1 (turn on motor 3)
etc.
In Arduino, you parse the code and use it accordingly. For instance:
serialvalue = Serial.read();
if (serialvalue == 65){
int motorstate = Serial.parseInt();
analogWrite(9, motorstate); // if 9 is output pin for motor 1}
else if(serialvalue == 66){
int motorstate = Serial.parseInt();
analogWrite(10, motorstate); // if 10 is output pin for motor 2}
etc.
Note: untested code, I'm just typing away here to give you an idea of the process. Basically what Source Audio was saying, I think.

Thanks - so basically we avoiding using string as an ID for each motor, rather we are using integer so it will be much easier to receive that data inside arduino.

Regarding the arduino code:
why to do if statement for each ID ? " if(serial.available == 65) " etc etc

why not just write:
if (Serial.available() > 0
?