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Connection of 3.3V PIR sensor on 15-20m cable - interference, voltage drops

Michal8883 594 8
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  • #1 21550677
    Michal8883
    Level 5  
    Is it possible to connect a 3.3v pir sensor on a 15-20m cable without any problems or will there be any problems?
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  • #2 21550731
    viayner
    Level 43  
    Hello,
    it is impossible to give a clear answer:
    - what is the sensor and what is the output signal? What is the output?
    - What is the receiver of this signal? What signals are expected on the receiving side?
    - what cable do you want to use? How routed? The presence of any interference?
    This is as a starting point.
    20 m is already quite a lot for digital signals, but to light up an LED is not a problem.
    Such a cable will bring a lot of delay to the signal edges, so here is the first potential problem.
    Inducing interference and lowering signal levels, meaning it can be difficult to detect whether it's an L, H or Z state.
    With such a long cable it is more likely that the output should be OC/OD type and loaded on the receiver side.
    Regards
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  • #3 21550957
    Michal8883
    Level 5  
    And the use of a relay and a 12v pir sensor
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    #4 21550998
    78db78
    Level 43  
    >>21550957 a signal across the relay contacts will take care of the matter.
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  • #5 21555806
    Michal8883
    Level 5  
    I was still thinking about the PC817 2 4 8 channel optocoupler isolation board voltage converter adapter module driver 3.6-30V photoelectric isolated module
    https://a.aliexpress.com/_EyBMzVk

    I don't know if it wouldn't be better than a relay?
  • #6 21555969
    JacekCz
    Level 42  
    @Michal8883

    You have not picked up the lifebelt given >>21550731 .
    What is the cable, how many wires, can you separate power and signal or not, what is the receiver ?
    You are treating a problem, but you yourself have not well defined what kind of problem.

    If (I infer from the posting in the section) an ESP32 is to mate with this, then 12V or 36V is of no use to you (without additional investment)
  • #7 21556095
    Michal8883
    Level 5  
    JacekCz wrote:
    @Michal8883

    You have not picked up the lifebelt given >>21550731 .
    What is the wire, how many wires, can you separate power and signal or not, what is the receiver ?
    12v pir good.
  • #8 21792354
    Michal8883
    Level 5  
    I want to connect a 3.3v sensor to the Olimex ESP32-POE-ISO-EA Development Board and run an Ethernet cable 30-50m. To the PoE switch and manage it. Will such a design work? Finally a second esp and a raspberry pi zero 2w with touch screen for management.
  • #9 21799169
    waltersalata
    Level 25  
    Michal8883 wrote:
    I want to connect a 3.3v sensor to the Olimex ESP32-POE-ISO-EA Development Board and run a 30-50m Ethernet cable. To the PoE switch and manage it. Will such a design work? Finally a second esp and a raspberry pi zero 2w with touchscreen for management.


    Connect like this.
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Topic summary

Connecting a 3.3V PIR sensor over a 15-20 meter cable can present challenges such as signal delay, voltage drop, and interference, which may affect the detection of digital signal states (Low, High, or High-Z). The type of sensor output, cable characteristics, routing, and presence of interference are critical factors. For long cable runs, open-collector/open-drain (OC/OD) outputs with proper loading on the receiver side are recommended. Using a relay with a 12V PIR sensor can simplify signal transmission over long distances by isolating the sensor output. Alternatively, optocoupler isolation modules like the PC817-based 2, 4, or 8 channel photoelectric isolated voltage converter driver modules (3.6-30V) can provide electrical isolation and signal integrity, potentially offering advantages over relays. When interfacing with microcontrollers such as the ESP32, higher voltage PIR sensors (12V or 36V) require additional components for voltage adaptation and isolation. Proper separation of power and signal lines and cable type selection are essential to minimize interference and voltage drops.
Summary generated by the language model.
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