wiring proximity sensor LJ18A3-8-Z/BX
i think this sensor is a normally off one
im trying to drop voltage with resistor, when i do so i get full volts from sensor wire , but when i test it like this it works - not sure why or whether it is a problem to wire like my diagram ?
The resistance of the S input is very high, so simply using a resistor in series won’t give much difference. You need to use a voltage divider (which is sort of what you have, but not the right way around). Try the circuit in this diagram I found off an instructables post: https://cdn.instructables.com/FQD/M93F/IGFEL3QB/FQDM93FIGFEL3QB.SQUARE2.jpg
FWIW: That is from the comments on this this post (comment made by mickeypop): http://www.instructables.com/id/Enable-Auto-Leveling-for-your-3D-Printer-Marlin-Fi/
thanks stuart, when i try to do it the right way i seem to get high voltage on S all the time no matter if sensor triggered
…any combination of resistor / divider that are connected back to negative(blue wire) result in full volts through sensor wire (black), but when i randomly sent volt back to brown (as per my picture) it works ?!, problem is i dont know why this happens or if it is safe, cheers ben
Essentially you’re gonna want a voltage divide to bring the voltage down to a 5v level that the board can handle. Some boards have built in protection but if you’re running a 12V setup you need a 15k and 10k. This video explains it:https://youtu.be/EcGFLwj0pnAhttp://youtu.be/EcGFLwj0pnA
Hi Griffin thanks for that, but i didn’t explain my situation very well. I am aware of the need to reduce voltage of signal wire to under 5 volts, i have followed instructions such as Tom’s guide, and instructables, including reading comments. The point is when i wire up voltage divider this way it doesn’t work for me, i get full voltage on sensor wire regardless of whether sensor triggered or not. But if i wire it up alternately, aka -my picture, it works, the difference is voltage divider sends volts back to positive wire instead of negative wire. Not sure why it is working this way for me, perhaps switch is different , damaged or wired up wrong, anyway I might just go with this method if it works and ignore to nagging feeling of naivety re. electronics, cheers Ben
this setup (pic above) ended causing smoke !!
update , i got myself a breadboard and tried again, When i try sensor attached to 9volt the sensor works putting out 9 volt (approx) when not triggered and 0 volts when triggered, light on sensor also works
when i test voltage divider directly attached to battery but not attached to sensor it reduced voltage to 2.4 volts on sensor wire, as per pic
But when i put sensor and voltage divider together all i get is approx 0 volts whether triggered or not
as well as registering 0 volts this setup , when attached to 12v ramps , does not trigger endstop status on marlin, so im doing somethink wrong , or sensor issue, (or perhaps the smoke i made before did something bad! ) cheers ben