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Monitoring low voltage with NPN transistor — Parallax Forums

Monitoring low voltage with NPN transistor

Luis_PLuis_P Posts: 246
in BASIC Stamp

Hello!!!
I have a device with output pins. One of the pins go high (1 volt) when is running an specific routine. I need to monitor that pin with the BS1 (or BS2). I was told I can use a NPN with a small resistor. I need to know what components to use NPN and resistor values, hook up diagram and Bs1 (or BS2) code. Any help would be really appreciated!!
Thanks to JonnyMac for the suggestion.

Comments

  • JonnyMacJonnyMac Posts: 9,159
    edited 2021-12-31 01:49

    Fair warning: If this circuit breaks something, I take no responsibility.

    On the left are the connections to the signal you want to monitor. It's a simple inverting buffer. When the input goes high, the point at "In" should drop from near 5V to near ground.

  • Luis_PLuis_P Posts: 246

    Thanks JonnyMac.
    A 2N3904 should work right?

    @JonnyMac said:
    Fair warning: If this circuit breaks something, I take no responsibility.

    On the left are the connections to the signal you want to monitor. It's a simple inverting buffer. When the input goes high, the point at "In" should drop from near 5V to near ground.

  • kwinnkwinn Posts: 8,697

    @Luis_P said:
    Thanks JonnyMac.
    A 2N3904 should work right?

    @JonnyMac said:
    Fair warning: If this circuit breaks something, I take no responsibility.

    On the left are the connections to the signal you want to monitor. It's a simple inverting buffer. When the input goes high, the point at "In" should drop from near 5V to near ground.

    2N3904 would be fine.

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