Filawinder servo mod idea (Page 1 of 2)

Hobby servos have a defined range of motion, typically limited by the pot that is used to indicated its position.

There are some continuous types available from various sellers. There are also some tutorials out there that show how to mod an existing position based motor.

Once you get into continuous types though, you need something to tell the servo to rotate opposite once it reaches its desired position. (end stop switch, optical etc.)

You could also use a stepper motor to do the same thing.

Continuous rotation servo:
https://www.adafruit.com/product/154?gc … LUQAvD_BwE

Some servos use an encoder disk instead of a pot. I have never seen a 360 pot. Do they even exist?

I was just going to say the same thing about the screw. That is how filabot does it.

The guide runs to and fro on a screw like the Z axis of a printer. A limit switch at each end triggers the direction change.

This works till something happens that causes the motor to miss a step or more. Then the whole thing is thrown off. That's why printers still use switches instead of steps due to reliability.

For the continuous rotation servo mod, IIRC, a gear is removed from the servo that connects the motor to the pot. Then another gear still connected to the pot is super glued in place to prevent the pot from ever turning again. This then forces the PID position loop in the servo to never reach its destination, and therefore it always remains turning until you send it a PWM command to stop.

The basic idea is, the pot is glued into place using super glue, and preferably glued into its middle of rotation position. Motor is commanded to turn in CW or CCW direction via PWM signal, and magnitude can be adjusted by how much PWM is sent. Since the pot never changes position, the motor never stops turning until you send it a PWM signal that adjust its "error" back to 0.

This is one way to do it:

https://www.instructables.com/id/Conver … -Rotation/

This is another way to do it:

https://learn.adafruit.com/modifying-se … n/overview

Does Tim know what PWM is output in the firmware?

Frequency and width?

I am working on replacing SERVO with a basic 12V motor that powers my own guide system.

Motor is triggered by 5V Relay.
5V has to come as ON and OFF from somewhere so i decided to use UNUSED pin from the board A4

Pin A4 is analog pin. It has output on the board (see picture below)

This works ONLY in AUTOMATIC mode.
Using modification in firmware from 2017 (see modification below) i added A4 pin as LOW (no power) by default
When filament drops low enough to activate the spool motor, A4 pin becomes HIGH (5V is ON)
That will trigger 5V relay.
5V relay will pass 12V coming from [Fan] pins through and activate my filament guide system.
The now 12V will enter into 2 sets of relays. Those relays are very special because they allow me to reverse motor direction by utilizing momentary switches. I tried multiple relays and countless switches, nothing will work but latched/bistable relay (see picture below explaining it)

I think i need to have 2 of those relays in order to reverse polarity to the motor based on which momentary switch is pressed at which relay.
Maybe i can use just one of those to trigger another basic 2 channel relay to to deversing ? Will see.

I have yet tested the mechanism using these relays so i dont know yet how i will wire it. No diagram as of right now.
But i have tested other relays and countless types of switches so i know those wont work no matter what you do.

I use Arduino 1.8.9
Required library: QTRSensors by Pololu
Library can be downloaded from Tools/Manage Libraries
=====================================================
=====================================================
Select:
Board/Arduino Nano
Processor/ATMega328p (old bootloader)
COM/What ever number device is connected to
Programmer/ArduinoISP
=====================================================
=====================================================
Open filawinder.ino
Locate:        pinMode(12, INPUT);
Add under:    pinMode(A4, OUTPUT); //added line

Locate:        digitalWrite(12, HIGH);
Add under:    digitalWrite(A4, LOW); //added line
=====================================================
=====================================================
Locate:    
void setMotorSpeed(int thisspeed)
{
  if (thisspeed<minimumPullerSpeed && (millis() - timeToMinimumSpeed < maxTimeMinimumSpeed)) {thisspeed=minimumPullerSpeed; }
  else { timeToMinimumSpeed=millis(); }

Change to:
void setMotorSpeed(int thisspeed)
{
  if (thisspeed<minimumPullerSpeed && (millis() - timeToMinimumSpeed < maxTimeMinimumSpeed))
  {
    thisspeed=minimumPullerSpeed;
    digitalWrite(A4, LOW);
  }
  else
  {
    timeToMinimumSpeed=millis();
    digitalWrite(A4, HIGH);
  }
=====================================================
=====================================================

How ever i am facing a problem.
Due to my lack of knowledge for Arduino programming, this was the best i could come up with.
Every 2-3 seconds there is a spike in voltage on pin A4. Its very small and nothing to worry about, but its annoying to see.
IF someone can suggest to place my custom parts of code elsewhere so there wont be spikes ? That be great.

The below image is a circuit that should allow you to do what you want and needs no logic to control it. Once it is started it should run by it's self. This is for 12 volt relays but there is no reason any other voltage can't be used. Just substitute 12 voltage line for whatever voltage you need.

Are those switches momentary or they have to be pressed/flipped ?
Can you word the process so i can understand it better ?
I am using arduino relay modules.
Thanks !

Easier said then done. I am a mechanic, not an electrical engineer like most of you. Some programming experience and basic electrical knowledge got me this far but not far enough to understand your setup with diodes.
Can you, using my picture, give each pin # a description ?
Thank you.
I'd rather use your system them mine. Mine is too complicated as i overthink allot of things in life including this.
This IS a 12V relay by the way.

Each channel is switched individually by connecting either 8 or 9 to 7 Gnd.
Is that what you need to know ?

I tried following your diagram.
Pretty sure i did it all right but its not working.
As soon as ground touches the coil, i get short circuit if diodes present.
Without diodes i basically get relay to trigger. I dont understand how grounding the coil through momentary switch would be any different.

Also its kinda hard to follow your diagram with the relay i have. I think i got the pins correct. Correct me if am wrong.