~ ANSWERED ~ If this is a repeat, my apologies - 4 servos all turning at once with one potentiometer...This is NOT the way the project is to work.  Please help

@Anna

Q:  What are the resistance values of your 4 potentiometers?  100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms, 10M ohms?

v = i * r

i = 5V / 100 = 50 mA per pot.

And what is the total capacity for the USB port driven supply on the UNO?  I think 200 mA.

The PC/laptop is capable of a maximum current drain of 100mA-500mA(max) and it is overcurrent protected.  Your mileage may vary.

@Anna

Q:  What are the resistance values of your 4 potentiometers?  100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms, 10M ohms?

v = i * r

i = 5V / 100 = 50 mA per pot.

And what is the total capacity for the USB port driven supply on the UNO?  I think 200 mA.

The PC/laptop is capable of a maximum current drain of 100mA-500mA(max) and it is overcurrent protected.  Your mileage may vary.

I had a look at this discussion last night, but unfortunately our IT department does some weird java filtering, so I can't reply.

Thanks Bill for the invite.

The suggestions made so far look correct, but I think the issue is in the analogue reading, not the proximity of the output wiring.

There is one thing that needs to be done.

The 5v supply unless its a large analogue model with knobs and meters, will be suffering from a lack of decent capacitors.

Please try to add one or two 1000uF or larger (multiples also work) across the servo 5v supply close to the actual servo.

Motors draw 3-4 times their running current when starting, and hence your little servos that are 100mA suddenly all turn into 3-400mA devices.

Coupled with the fact they are all incorrectly driving at the same time, and they all beat each other to death.

The Arduino reference has mixed messages regarding the name to use for the Analogue inputs.

A0, 0 all seem to work BUT it has to know its doing an analogue reading.

It does clearly say to connect the other pins.(as Nico pointed out)

If the analog input pin is not connected to anything, the value returned by analogRead() will fluctuate based on a number of factors (e.g. the values of the other analog inputs, how close your hand is to the board, etc.).

Delay

The examples all use a delay(15) to allow the servo to actually get there, before trying to change where it is.

This may be enough but will depend on the loading and performance of the servo.

Annasta

I suggest trying your single pot on potpin0 (A0) but with the others (potpin1,2,3) shorted to ground (or use a 1k to 10k). This ensures their value is known to be zero.

I also recommend sending the value to terminal so you can see what is happening.

I've also added a delay to slow it all down. You need something to allow the servo to get there.

hence

#include <Servo.h>

Servo myservo0;  // create servo object to control a servo
Servo myservo1;  // i added
Servo myservo2;  // i added
Servo myservo3;  // i added

int potpin0 = 0;     // analog pin used to connect the potentiometer (i added the zero to the potpin before the equal sign)
int val0;               // variable to read the value from the analog pin

int potpin1 = 1;    // i added
int val1;               // i added

int potpin2 = 2;    // i added
int val2;               // i added 

int potpin3 = 5;    // i added
int val3;               // i added

void setup()
{

Serial.begin(57600);

  myservo0.attach(5);       // attaches the servo on pin 5 which conicides with A0 object potpin 0
  myservo1.attach(7);       //  i added pin  7 which conicides with A1 to the servo object potpin 1
  myservo2.attach(8);       //  i added pin  8 which conicides with A2 to the servo object potpin 2
  myservo3.attach(12);     //  i added pin 12 which conicides with A5 to the servo object potpin 3
}

void loop()
{

  val0 = analogRead(potpin0);            // reads the value of the potentiometer (value between 0 and 1023)
  val0 = map(val0, 0, 1023, 0, 179);     // scale it to use it with the servo (value between 0 and 180)
  myservo0.write(val0);                  // sets the servo position according to the scaled value

  Serial.println(val0, DEC);

  val1 = analogRead(potpin1);            // i added
  val1 = map(val1, 0, 1023, 0, 179);     // i added
  myservo1.write(val1);                  // i added 

Serial.println(val1, DEC);

  val2 = analogRead(potpin2);            // i added
  val2 = map(val2, 0, 1023, 0, 179);     // i added
  myservo2.write(val2);                  // i added

  Serial.println(val2, DEC);

  val3 = analogRead(potpin3);            // i added
  val3 = map(val3, 0, 1023, 0, 179);     // i added
  myservo3.write(val3);                  // i added

Serial.println(val3, DEC);

delay(300);          //add the delay back in and slow the whole thing down.
}

I also recommend slowing down the loop, as the analogRead only takes 0.001 seconds.

See how this goes, and then we can look at some other diagnostic tricks like forcing the servo to a known value.

Mark

Hi

Just to confirm Mark's statements...

"The Arduino reference has mixed messages regarding the name to use for the Analogue inputs.

A0, 0 all seem to work BUT it has to know its doing an analogue reading.

It does clearly say to connect the other pins.(as Nico pointed out)"

To add to answer on analog pin naming. I was curious about this as I knew the A0, A1 ... etc were constants but I had never checked what value they represented.

Well ...A0 is a constant equating to 14, A1 = 15, A2 = 16 ... and so on but in the analogRead function, A0 and 0 are treated as A0, A1 and 1 as 1, etc

And on A/D pins

-----------------------

Unconnected analog inputs tend to track the value on the connected input(s).  This I proved by experimentation by connecting a pot on A0 and leaving the rest unconnected.  The results were:

A0 = 495

A1 = 486

A2 = 476

A3 = 465

... and as I varied the pot and A0 followed steadily, A1,2,3 all followed along, albeit, shifting somewhat randomly around the A0 value.

This will explain the servos being tied together

Hope this helps

Terry

@Mark -

Hello Mark, I just seen your post, and after seeing everyone go nuts about me using the non digital pins, I figured I would just go back to them.

I posted a pic of my wiring diagram.

I have no problem trying out your coding, its an easy change back to the non digital pins if needed; just a question if I may....if I do use the digital pins, all i need to do is change the int potpin numbers, and the myservo.attach(*) to 3, 5, 6, & 9 ?

I just dont get why these wont work...I am so trying to get this.

As far as the UF's what is the lowest to highest number I can use, and also if I understand correctly you want me to connect one to each servo motors ground?

~Anna

Annasta

I think the servo library documentation gave a hint as to what pins to use, and I believe they were the ones handling PWM.

re capacitors

The general rule with any power supply is you have 1000uF per amp.

Assumming your power supply has some capacitors, then 1000uF should help.

You place them between the 5v of the servo supply and ground as close to the servo as you can.

You may get a way with 4 x 470uF across the 5v and gnd at each servo, and it will work.

Do you have access to any capacitors. (They need to be greater than 5volts).?

Your drawing shows the final configuration with 4 pots installed.

I don't suppose you've tried it with all 4 connected.?

Mark

Anna,

Mark's final question is the one the one that I'm  still not clear on.

Bill,

servo 'standards' are really quite loose and there is no completely accepted standard. Most are close enough to be interoperable. The two biggest radio manufacturers have 1500uS and 1520uS as their defined centre point. Even this is not always true, as some specialised type have a shorter mid point e.g. 760uS so that the updates can be faster. This would be the case for a tail servo for a helicopter where the gyro needs to update quickly to give a good tail control.  Normal update rate is about 50Hz but most digital servos will accept faster than this. Analog ones will burn out. As far as I know, all servos will give a change of output position of about 90 degrees for a change of input pulse of 1000uS. This is subject to manufacturing tolerances. Due to manufacturing tolerances it is not possible for this travel to be at the ends of the internal feedback pot so that they will travel beyond + and - 45 degrees of neutral if the input signal extends beyond the + and - 500uS of the nominal neutral. Exactly how much depends on the individual servo. I do not see any advantage in trying to use this extended range as if the servo motion is being converted into a linear motion by say a push rod, then beyond+/- 45 degrees the motion becomes very non linear. Radio control sets will use a little of this extended travel to allow trimming of the centre position to compensate for manufacturing tolerances in the servo and in the model setup.

I have just tested a random sample of the 40 odd servos of various makes and types that I have and they all conform to these numbers. (judged by eye) In practise the difference between 1500 and 1520 neutral is unimportant as some form of trimming is usually needed. However there may be strange ones out there, some early ones I beleive had a neutral of about 1300uS.

For anyone not sure the difference between analog and digital servos it is in the processing and drive of the motor, not the form of the input signal. (Other than the rate as mentioned above)

Chris

@Mark -

Mark I have approximately 75 capacitors.  Using the line number, can you tell me which ones I can use for optimal performance

Note I have also attached a pdf file if this list doesnt show up nice.

~Anna

Annasta

A single capacitor from Line 18 down will help when placed across the 5v servo supply.

BUT

What happened to the other suggestion and question posed earlier ?

1.     I suggest trying your single pot on potpin0 (A0) but with the others (potpin1,2,3) shorted to ground (or use a 1k to 10k). This ensures their value is known to be zero.

2.     I don't suppose you've tried it with all 4 connected.?

Is there a reason you don't want to try our suggestion.?

Mark

@Mark -

No fears, i wanted to get this over to you..being saturday I had to photograph some students for their senior prom

~AnnA