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LMR14050: 24VDC or 3.3VDC line will generate sparks when it got shorted with Ground?

Naveen K1
Intellectual 870 points
Part Number: LMR14050
Other Parts Discussed in Thread: LM1085

Hi,

We have one important question, it should be a safety solution. We need sensor to install in two applications.

  1. Indoor Application: In this case, sensor will be installed in a room near to the Nitrogen, Ammonia gas cylinders. Sometimes leakage(or normal small leakage) may happen. Leakage may cause corrosion.
  2. Outdoor Application: In this case sensor will be installed in outside open space environment near to the Nitrogen, Hydrogen, Ammonia gas cylinders. Sometimes leakage may happen and rain will fall on the sensor.
Sensor will be connected to our CC3220MODSF board and Using LMR14050SDDA for 24V out , LM1085 for 3.3V out. Sensor supply voltage range will be 6-36VDC, We will supply 24VDC. We need to provide safety solution due to leakage gas may present in the environment and should not cause firing due to sparks from DC short circuit.
Query:
1. If Sensor cables(24VDC and Ground lines) got shorted accidentally, Any spark will generate? 
Kindly suggest us to install and power up for the sensors in a safety methods.
Thanks and regards,
Naveen K
  • 0
    TI__Mastermind 46081 points

    Hello Naveen 

    Yes, a spark can happen by shorting any two live wires. Even if a low-voltage system has a potential for igniting explosive materials/gas as high-voltage system. In general, designers try to use lower voltage rails , minimize the stored energy in the system and coat/cover/isolate the circuit which is exposed to hazardous location in order to minimize the risks. I haven't had a chance to design a system following IEC/EN 60079, NFPA497, but you may need to read these through and follow the standards.  

    (This information is for reference purpose only and TI does not guarantee the accuracy. Buyer/User is solely responsible for the design, validation, and testing of its applications as well as for compliance with all legal, regulatory, standards, and safety-related requirements concerning its applications.) 

    - Eric Lee (Applications Engineering) 

  • 0 in reply to EricLee
    Intellectual 870 points

    Hi Eric Lee,

    Thank you for the information.

    Sure, we will consider your advices for reference only we do take care all safety related.

    1. We are using proximity sensor, There is no extra SAFETY benefit either if it is a Capacitive or Inductive type, right?

    2. To reduce the power, we will supply 9V to the sensor from external adapter with a 100 ohm series resistor, It will reduce the chances to generate sparks when short, right?

    3. Coat mean, Conformal coating? What material could you suggest?

    4. Am not sure, found right documents/links for IEC/EN 60079, NFPA497. Could you please share the datasheet/link.

    Thanks and regards,

    Naveen K 

  • 0 in reply to Naveen K1
    TI__Mastermind 46081 points

    Hello Naveen

    1. I think this is outside of Power Management forum's topic. In general, you have to select the type of the proximity sensor depending on which object you want to detect. Non-metallic object can be detected by Capacitive sensor. 

    2. A current limit resistor can reduce the chances to generate a spark, but the potential for igniting explosive materials/gas still exist.

    3. I think this is outside of Power Management forum's topic. Please follow the IEC / NFPA standards. 

    4. Please visit https://www.ul.com/      https://www.nfpa.org/ 

    (This information is for reference purpose only and TI does not guarantee the accuracy. Buyer/User is solely responsible for the design, validation, and testing of its applications as well as for compliance with all legal, regulatory, standards, and safety-related requirements concerning its applications.) 

    - Eric Lee (Applications Engineering) 

  • 0 in reply to EricLee
    Intellectual 870 points

    Hi Eric,

    Thank you for the information.

    It's intension is to protect the device/power supply as well as safety by adding any possible additional component on power lines to avoid/minimize the chances of issue.

    We will tack care on Assembly safety precautions, but we want to know/implement the design in safety manner as possible/available. Main concern is power lines.

    Last clarification on your advice.

     "A current limit resistor can reduce the chances to generate a spark, but the potential for igniting explosive materials/gas still exist."

    1. Please see the attached circuit, All 4 cases generates spark, if point A-B got shorted? Which case may reduce the chances to generate a spark ?

    2. Not possible to avoid the sparks even if same line on point A-B got shorted (Case1,2) ?

    Thanks and regards,

    Naveen K

  • +1 in reply to Naveen K1
    TI__Mastermind 46081 points

    Hello Naveen 

    The chances to generate sparks reduce by limiting the current, reducing the voltage and minimizing the parasitic inductance of the cable. 

    The chances to create a flame exist  when the short is caused by a thin material which cannot handle 5mA (Case1), 2.5mA(Case2), 24mA(Case3), 12mA(Case4)

    (This information is for reference purpose only and TI does not guarantee the accuracy. Buyer/User is solely responsible for the design, validation, and testing of its applications as well as for compliance with all legal, regulatory, standards, and safety-related requirements concerning its applications.) 

    - Eric Lee (Applications Engineering) 

  • 0 in reply to EricLee
    Intellectual 870 points

    Hi Eric,

    Thank you for the information.

    Thanks and regards,

    Naveen K

  • 0 in reply to Naveen K1
    TI__Mastermind 46081 points

    Thanks for choosing TI. Please feel free to contact us if you have any questions.
    - Eric Lee (Applications Engineering)