Reed Contacts with Distance?
Hey Together!
I have 2 wired reed contacts, the first one is directly wired with my homeduino, the other is wired with ca 2,5-3 meters cable to the homeduino. The first works correctly, the other one changes fast between Open and closed. Can somebody gimme tips, how i can fix it?
Greets
Dodo
@Dodo88 Referring to https://github.com/pimatic/pimatic-homeduino/issues/83 my suggestion to use a lower resistance for the long cable. Try 4.7k or 2.2k Ohms. If you have it at hand, also add an 0.1 uF Capcitor between IN and Ground.
What kind of cable do you use?
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law
@mwittig
i didn’t use any resistor, because the resistor is build in the reed contact i think. I don’t know what resistor is build in…
and the cables, i can’t say the thickness, but it’s a little more than lan-cables i think. i use the same cables with more than 4 meters for the dht22 in my bedroom. if you give me your mail adress, i send you a photo from the reed an the cables?
greets
here is this reed-kontakt. He comes from Automotive industrie, and works normally with 12v as i know. An all the electricity is build-in in this small contact. Should i test it with 12v, and the Data pin to homeduino? or would it damage the arduino nano
This will destroy your hardware. If you want to work with 12V you have too work with a voltage divider at the data pin to the Homeduino and commond ground.
I have tried to look up the datasheet, but I could not find the datasheet for this specific part, but a few others of the same product line:
Note, all NBN4-F29A type sensors appear to be inductive sensors rather than magnetic switches. Such sensors contain a frequency oscillator that creates a field in the close surroundings of the sensing surface. The presence of a metallic object in the operating area causes a change of the oscillation amplitude. This amplitude change is identified by a threshold circuit that changes the output state of the sensor. If your sensor matches up with the other NBN4-F29A type sensors it should have an indicator LED and screw to control sensitivity. The input voltage varies from model to model, however, as the sensor basically works with homeduino using the short cables 5V should be with the acceptible input range. I suppose you sensor has three wires, right?
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law
okay thx, i thought it could destroy the nano…can i find out wich resistor is build in? if i connect the original cable on the arduino with 5v, it works great. should i add the 4.2k resistor (zusätzlich) on the long wire?
oh i didn’t see that you already answered. yes my Sensor has 3 cables, but no led or screw for sensibility. @mwittig
@Dodo88 said in Reed Contacts with Distance?:
can i find out wich resistor is build in
Well, possibly you can measure it if you have multi-meter at hand. Anyhow, you can also try to connect a resistor as described above. Did you try this already? Btw, I don’t think the sensor has a built-in resistor, however, you want to try with a small value first, say 1K. Also the capacitor might help as suggested. Moreover, you could also try a different cable, e.g. use a shielded cable (connect shield to ground in case).
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law
That the sensor with the short wire works, shows that 5V is OK. But a wire has allways a resistance.
At the long wire comes maybee only 4V to the sensor (you can measure this with a multimerter) and this is too low that he works correct.
So you can take a bigger wire what reduced the resistance or you have to go with a higher voltage.
But then you have to use a Spannungsteiler or a Zener-Diode on the data line to the arduino.
I don’t think a simple resistor can help you because you don`t use a reed contact.
@V1per said in Reed Contacts with Distance?:
But then you have to use a Spannungsteiler or a Zener-Diode on the data line to the arduino.
The following thread might be helpful which outlines various options.
https://electronics.stackexchange.com/questions/43498/how-can-i-use-a-12-v-input-on-a-digital-arduino-pin
"It always takes longer than you expect, even when you take into account Hofstadter's Law.", Hofstadter's Law
okay my multi meter shows 4,5v @ the end of wire. i think i will use wireless magnet contacts for my project to read the status of my door. found cheap ones on e… for 3€ each one.
thanks for your help, i will test it again with thicker cables anytime 
greets Dodo
