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Currently I'm making a platform for hardware and I'm considering adding the ability to auto detect the required power supply voltage of attached sensors - this will be either 3V3 or 5V.

How can automatic detection of the required power supply voltage for a sensor be achieved?

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    \$\begingroup\$ Your question needs to be rewritten. It is not possible to be certain what you want to do. Do you want to use either 3.3 or 5V power supplies - and what is the system voltage. Or 3.3 or 5v sensors. Or ...? What does "usage" mean? \$\endgroup\$
    – Russell McMahon ♦
    Commented Sep 15, 2013 at 4:32
  • \$\begingroup\$ i want to know what voltage the sensor use is it 3.3 or 5 volt then i could give the right voltage to sensor's vcc. what is the best title then? \$\endgroup\$
    – Rijdzuan Sampoerna
    Commented Sep 15, 2013 at 4:38
  • \$\begingroup\$ May I recommend, "How to automatically detect the required voltage for a power supply sensor?" And in your question you specify that you have 2 sensors, one using 3.3V and the other 5V; and that you need to find out which sensor is connected so that you can supply the correct voltage to it. That's assuming that I've understood the question correctly to begin with, which I can't guarantee. \$\endgroup\$
    – nonsensickle
    Commented Sep 15, 2013 at 5:03
  • \$\begingroup\$ Oneitusatu - the title is fine - but the question wording should contain enough information in it to allow people to understand what you want. When read by itself without reference to the heading the question makes no sense. People like Olin are unable to bring themselves to combine the heading and the body text when trying to understand a question. \$\endgroup\$
    – Russell McMahon ♦
    Commented Sep 16, 2013 at 9:07
  • \$\begingroup\$ Using all small letters or all large letters in your text makes you appear lazy or rude to some people. You can afford to ignore some people if you are very rich, know everything and don't want your questions answered, if you wish. Otherwise it is very wise to stick to standard use of capitals. If there is some good reason why you cannot do this you should explain wh.y \$\endgroup\$
    – Russell McMahon ♦
    Commented Sep 16, 2013 at 9:10

1 Answer 1

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You could

  • use two pins, provide 5V on one and 3V3 on the other, and wire the sensor accordingly.

  • provide 5V, and let the sensor derive 3V3 from it if it needs that voltage

  • use an LM317-style regulator and let the sensor provide one of the resistors that determine the output voltage

  • provide a constant current, and have an appropriate zener diode in the sensor. fore extra points, modulate the drop voltage to communicate the sensor value back to the host.

  • start at 3v3, have a microcontroller in the sensor, which communicates with your host to ask it to raise the voltage to 5V if it needs such for its sensor

If the sensor needs to be low cost and an extra power pin is no trouble the I would choose the fist option. If adding a pin is a nono the second seems a good choice. The third would be OK only when you need a wide variety of voltages, and can't put the regulator in the sensor. The last is for completeness only, there are products that work this way but for a sensor it feels much too complicated.

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