Capacitive sensor with mechanical endstop

Hello

I want to use my old and very reliable makerbot 1.2 endstop with three wires with my brand new capacitive sensor(I do not trust that It is so reliable)

I am using a circuit with an optoacopler like this one Circuit

I do not know what I am doing wrong, but It does not work....so the question is:

Is it possible to have both endstop and capacitive sensor working ant the same time? what do i have to do?

would it be possible to use the zmax pin as a second zmin switch,....as I am not using it.

thank you all!!

I am using RAMPS 1.4


If this is the right place to ask for these kind of questions let me know.

You could have both endstops connected to the same pins on the ramps as long as they both trigger Normally open (NO) i.e. switch from 0v open to 5v triggered. That way if they are both open, the voltage on signal pin is 0v but if either one triggers the voltage becomes 5v.

If they are normally closed (NC), then they will both be sending 5v to the signal pin. If one sensor triggers and switches to 0v, the 5v will still be supplied by the other so it won't show as triggered. This will offer you no safety or reassurance as it will not work unless both sensors trigger.

I'd do away with the mechanical z-min endstop and configure a NC (PNP type) z-probe sensor and trust it to work. If it fails it will show triggered and your printer will not crash the bed. However that is often a bit more hassle to do than using a NO (NPN) sensor like the one you have. These are easier to setup as they ground the signal pin and do not run the risk of sending 12v down your 5v signal line.With a NC sensor (PNP) use a voltage regulator make sure the 5v is always 5v even if you input 12v from the sensor. The problem with NPN is that is is normally open, which will not give a triggered signal if it fails, therefore can cause head crashes. The solution is just to test it before each print by placing an object under it and sending m119 to check it is working, then home, autolevel and print.

Edited 1 time(s). Last edit at 10/26/2015 01:56PM by DjDemonD.

Thank you for your detailed answer.

In the end I am using the latest RELEASE CANDIDATE OF RAMPS, V2,..which has a new feature, you can have a separate pin for you autolevel device...This feature is what I was looking for...

  // Support for a dedicated Z probe endstop separate from the Z min endstop.
  // If you would like to use both a Z probe and a Z min endstop together,
  // uncomment #define Z_MIN_PROBE_ENDSTOP and read the instructions below.
  // If you still want to use the Z min endstop for homing, disable Z_SAFE_HOMING above.
  // Example: To park the head outside the bed area when homing with G28.
  //
  // WARNING:
  // The Z min endstop will need to set properly as it would without a Z probe
  // to prevent head crashes and premature stopping during a print.
  //
  // To use a separate Z probe endstop, you must have a Z_MIN_PROBE_PIN
  // defined in the pins_XXXXX.h file for your control board.
  // If you are using a servo based Z probe, you will need to enable NUM_SERVOS,
  // Z_ENDSTOP_SERVO_NR and SERVO_ENDSTOP_ANGLES in the R/C SERVO support below.
  // RAMPS 1.3/1.4 boards may be able to use the 5V, Ground and the D32 pin
  // in the Aux 4 section of the RAMPS board. Use 5V for powered sensors,
  // otherwise connect to ground and D32 for normally closed configuration
  // and 5V and D32 for normally open configurations.
  // Normally closed configuration is advised and assumed.
  // The D32 pin in Aux 4 on RAMPS maps to the Arduino D32 pin.
  // Z_MIN_PROBE_PIN is setting the pin to use on the Arduino.
  // Since the D32 pin on the RAMPS maps to D32 on Arduino, this works.
  // D32 is currently selected in the RAMPS 1.3/1.4 pin file.
  // All other boards will need changes to the respective pins_XXXXX.h file.
  //
  // WARNING:
  // Setting the wrong pin may have unexpected and potentially disastrous outcomes.
  // Use with caution and do your homework.
  //
  //#define Z_MIN_PROBE_ENDSTOP

#endif // AUTO_BED_LEVELING_FEATURE

With this I am pretty secure, that I will not make a total failure with the bed....and the sensor...

Thank you...