Designing a Circuit to Detect PNP and NPN Sensors

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Discussion Overview

The discussion revolves around designing a circuit to detect whether a sensor is PNP or NPN. Participants explore the requirements for powering the sensors with batteries and how to indicate the type of sensor using LEDs based on the output type. The conversation includes technical considerations and circuit design challenges.

Discussion Character

  • Homework-related, Technical explanation, Exploratory

Main Points Raised

  • One participant outlines the project requirements, specifying the need for a circuit that uses two 9V batteries and indicates the sensor type with two LEDs based on whether the output is sourcing (PNP) or sinking (NPN).
  • Another participant suggests starting with a circuit that uses one LED, proposing that adding a second LED should be straightforward with an additional transistor.
  • A different participant expresses the desire to maintain three wire inputs for the sensor, indicating that both LEDs should be connected to the same point and activate based on the output type from the sensor.
  • One participant proposes converting the PNP/NPN distinction to a low potential/high potential distinction to simplify the design, suggesting that having both LEDs share a common connection to the power source could be feasible.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the specific circuit design. Multiple approaches and ideas are being discussed, indicating that the design remains unresolved.

Contextual Notes

There are limitations regarding the assumptions made about the circuit design and the specific configurations of the LEDs and transistors. The discussion does not clarify all mathematical or technical steps involved in the proposed designs.

DSelfridge
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Homework Statement



Workinfg on a project for a teacher currently and need help designing the circuit for how to detect whether a sensor is PNP or NPN. I need to have 2 9V batteries power the NPN or PNP sensor and then have a spot for the third wire, where if it is positive output (PNP) (sourcing) then one LED lights up, whereas if it is negative output (NPN) (sinking), then a different LED lights up. Any help?
 
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Try to make a circuit with one LED first, I think the second one should be easy to add with an additional (known) transistor afterwards.
 
Well I understand that but I only want to have 3 wire inputs for the sensor which then has both LED's tied to the same spot just each turns on depending on whether it gains a sourcing or sinking output from the sensor? does that make sense? I don't really know what to do for that, a bipolar transistor?
 
Just 3 connections for the LEDs? That's still possible.
Try to convert "pnp<->npn" to "low potential<->high potential" (somewhere) first.
Just 3 connections are easy if both LEDs can share a common connection to the power source (positive or negative side).
 

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