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Induction Probe and Bed leveling systems
I am not really an electronics guy, but I will put down here what I have been able to find about adapting the Printrbot inductive probe to a new Controller board (Motherboard) The main Adaptrboard Wiki does not seem to be getting updated with these so I am trying to fill that need here (I am probably not commiting them properly).
There are a number of ways to adapt the Induction Probe to operate on a new board. First we need to understand why you cannot just plug it in and hope it will work. The Induction Probe operates at a wide range of voltages. The one in the Printrbot is 6V to 36V range. But the Z switch you would normally connect it to is 5V at best and could be 3.3V. (YOU NEED TO CHECK THE LIMIT SWITCH VOLTAGE SPECS FOR YOUR PARTICULAR BOARD see note: 1) When tested these probes will not normally operate at all, or reliably at 5V. (There are a number of times it has been commented that they will work at 5V, but I remain confident this will lead to trouble, sooner or later, and better to avoid problems.) If you power them at 6V, 12V, 24V the sensor output is at that same voltage. Connecting directly to the board at any of these voltages WILL damage your board. Conversely the probes are more accurate at the higher voltages. Voltage does NOT increase their detection distance. So we have to get higher voltage to the probe, but not let that voltage be seen by the board.
NOTE: The easiest method will be an Adaptrboard by Philip Mally. Designed to be plug and play and should work on a number of different boards. This board uses a transistor according to Philip Mally.
These are the methods I have seen listed; Use an optocoupler; Use a voltage divider; Use a diode; Use a transistor; Use a voltage regulator;
This is the method I chose on my upgrade. It was well documented and the parts were easily available. It is not the cheapest method due to the cost of the optocouplers but they respond very quickly and are reliable. They also can be done without soldering. I recommend you not use one of the relay style boards as they may not respond quickly enough to reliably set your Z Height. Because it acts like a switch, e.g. it is 0V until tripped and whatever the Logic voltage is when tripped (3.3V or 5V most common) it should not be effected by the Logic voltage of the board. It is powered by the same voltage as the probe high end. How to setup auto bed leveling, induction probe wiring an optocoupler
The only thing I noticed wrong in this video is that he stated that higher voltages increase the detection distance, it doesn't. Plus he shows a Normally closed rather than the Normally Open. Remember this video is for a different board and may or not have pullups or pulldowns activated that will effect the operation. These differences are handled in the firmware settings. "Normally Open" is what is set in Philip Mally's firmware already, as that is what the induction probe is in a stock printrbot. So you just need to get the voltage down to a safe level. You must determine the "Logic voltage" of the board you intend to use with this. If the logic is 5V then you have to bring it down to that voltage. If it is 3.3V, again you have to bring it down to this voltage. Different resistors will be needed for each voltage. Induction sensor, voltage divider.
Again I did not choose this method as I could not find enough sources to give me confidence in protecting my board. Lots of mentions of using a diode, very little information on how. Induction probe with a diode.
Truthfully I have found nothing about how to use a transistor to run the inductive probe. But this is what Philip Mally uses in his Adaptrboards. I am sure I could figure this out screwing around on a breadboard. Basically when the sensor is triggered the transistor will act as a switch does, sending voltage to ground. Not sure But I think the transistor will handle 3.3V or 5V logic.
Not a lot on this either, but have seen it mentioned here and there plus have seen the sensors being sold with a regulator in Amazon and other stores. The Regulator is always a 7805 (5V). I found this one article that has a diagram of wiring up the regulator in a rep rap wiki article. If the Board Logic is 3.3V you will need to use a 7803 Linear regulator instead of a 7805 Linear regulator. Always check the logic voltage of the board to determine the correct parts for your build. Z probe Rep Rap
The BlTouch is a servo driven probe. The servo lowers the probe into the detect position. Then the z lowers until this pin is tripped. The BLTouch is not as accurate as an induction probe. That said, IT is accurate enough. The BLTouch is tolerant of 3.3V logic and 5V logic So it can work on many boards. BLTouch V3.1 specs
Really need someone that is an avid electronics hobbyist, to step in, to fill the canyon sized gaps in this page!
NOTE:1 SKR Mini E3 V2.0: It has 3.3V logic instead of 5V. I don't think this will effect my Optocoupler, it acts like a switch anyway, but it will effect a voltage divider circuit resistors choice and maybe the Diode choice. Not sure, but I think the Adaptrboard will be fine also Philip Mally will know. And if you are using BLTouch you will be ok as it can operate at 3.3V or 5V. This is why it is important to read the Board Specs before you buy it or to accommodate its Logic voltage.