I'm using an ESP8266 so I'm limited to 3.3v. I've found a number of inductive proximity sensors but they require 5v or more. Does a 3.3v sensor exist?

I recently dropped some tiny screws on dark carpeting and would like to find them instead of just vacuuming them up. Stupid project? Maybe. But a good excuse to buy another sensor.

  • 4
    Have you tried using a magnet?
    – Gerben
    Feb 21 '17 at 9:22
  • i've not had many problems w/ 5v sensors w/ESPs. If its a digital output, that's easy enough to use a transistor or dropper diode on (or nada). w/analog output, it's easy enough to use a voltage divider...
    – dandavis
    Feb 21 '17 at 14:18
  • 1
    Why use a magnet when I could build something?
    – acpilot
    Feb 21 '17 at 15:15
  • if you want really cheap, try some of these ideas: newark.com/pdfs/techarticles/microchip/… if none of the doezen or so ideas work, bite the bullet and get some 2-way level shifters on ebay like these: ebay.com/itm/132091293479
    – dandavis
    Feb 21 '17 at 17:52
  • An inductive sensor may not see "tiny" screws very well, and if it does it may well also see things you don't care about, like nails in the underlying flooring. In contrast a magnet will pick up the screws. Then you can use them to make a more suitable project. Jun 21 '17 at 18:13

I don't know what voltages inductive proximity sensors use, but in general it's inexpensive to use 3.3V–5V logic level converter modules. These typically are bi-directional interfaces that use an N-FET and pullups to the two supply voltages to interface different-voltage logics. See the "Bi-directional level shifters" section of the TAKING IT TO ANOTHER LEVEL: MAKING 3.3V SPEAK WITH 5V article at hackaday.com for a circuit explanation. See gearbest.com and sparkfun.com and Adafruit for inexpensive modules.

Note, for finding small screws in carpet, a search coil as used in a metal detector might be a better choice than a proximity sensor. The coil is part of a tuned LC circuit; metal near the loop detunes the circuit slightly, producing a tone by heterodyning.

  • Those "inexpensive" devices cost more than an ESP8266 MCU...
    – dandavis
    Feb 21 '17 at 17:51
  • @dandavis, can you give a link to an ESP8266 MCU that costs less than $1.21, the gearbest module cost delivered? Feb 21 '17 at 19:16
  • I wish! haha ;) tbh, I didn't see that one, just the paytafruit and the other...
    – dandavis
    Feb 21 '17 at 20:13
  • You could probably just use a resistive divider to bring the 5V down to 3.3V.
    – Alex
    May 23 '17 at 2:06

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