LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 04:53AM |
Registered: 6 years ago Posts: 15 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 05:15AM |
Admin Registered: 13 years ago Posts: 7,005 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 06:01AM |
Registered: 6 years ago Posts: 15 |
What happens if I don't do this step?Quote
Dust
but make sure you turn off the pull up resistor of your probe pin in firmware.
I don't have these resistors I only have 10K and 3.3K and these:Quote
Dust
use 3.6 kΩ and 9.1 kΩ for 12v to 3.1 volt
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 06:26AM |
Admin Registered: 13 years ago Posts: 7,005 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 07:12AM |
Registered: 6 years ago Posts: 15 |
Quote
Dust
"What happens if I don't do this step?"
The pull up resistance becomes part of the voltage divider ( Arduino Due, it is between 50kΩ and 150kΩ. in parallel from signal to vcc) and the output voltage is wrong. (higher than wanted, worst case 3.4v enough to damage a 3.3v IO line)
"But with 10K and 3.3K I get 2.977 volt will that be enough or does it need to be closer?"
should be fine, anything over 2v should be accepted as a high.
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 02:57PM |
Registered: 6 years ago Posts: 265 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 03:43PM |
Registered: 6 years ago Posts: 15 |
Thanks for the tip about the 1N5817!Quote
MMcLure
Another possibility is to just use a reverse-biased schottky diode like a 1N5817 instead of a divider network. Connect the cathode (striped end) of the diode to the signal wire from the sensor, and the other end of the diode to the microcontroller pin, and turn ENDSTOP_PULLUP_Z_MIN on. When the sensor is not sensing anything, the diode will block the voltage and the pullup will pull the signal pin high, when the sensor triggers it will pull the signal pin low through the diode. No need to calculate resistor values for a divider.
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 04, 2019 04:53PM |
Registered: 6 years ago Posts: 265 |
Quote
unf0rg0tt3n
Thanks for the tip about the 1N5817!
What microcontroller pin do you mean, because by "ENDSTOP_PULLUP_Z_MIN" I think you mean the endstop Z_min?
I't still on I have my mechanical end stop still connected.
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 05, 2019 02:34AM |
Registered: 6 years ago Posts: 15 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 05, 2019 02:37AM |
Registered: 10 years ago Posts: 14,672 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 05, 2019 06:58AM |
Registered: 6 years ago Posts: 15 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? March 31, 2019 09:51PM |
Registered: 6 years ago Posts: 265 |
Re: LJ12A3-2-Z/BX onto RADDS 1.6 Board? April 01, 2019 02:01AM |
Registered: 6 years ago Posts: 15 |
I got it all working now, at around 2v is measured high, your idea will work just fineQuote
MMcLure
I measured a 1N5819 at a reverse leakage current of 61uA at 12.5V. Is that really enough of a leakage to be concerned about in this application? I'm wondering because I'm planning to upgrade to a 3.3V board myself.