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I need to allow two devices to communicate by generating a set of pulses (in the range of 100 to 1K HZ) in one device to be received by another device. The two devices are very near each other (say 5mm) and both devices have their own power.

I could create two pins to connect the two devices, but this means that I need to design a case that connects the two pins and make sure that they always connect in the field.

Can I transfer these pulses using a contact less method? The solution should be very cheap (less than 1USD) and low power (less than say 1mw consumption). So solutions such as NSF and BLE and .. are not suitable due to cost and power consumption.

What are some alternatives to design a way to communicate pulses between two devices sited close to each other without physical wires?

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    As it stands I can't see any connection to IoT in this question, and as such is off topic – hardillb Oct 12 '17 at 16:56
  • Can you explain why this is the only possible means of communication, and there are no alternatives? – Mawg says reinstate Monica Oct 13 '17 at 17:41
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I am not sure as to cost however here is some investigation into using LEDs to communicate light pulses.

How to Use LEDs to Detect Light is a short article with diagrams for using a pair of LEDs to send and receive light pulses.

LEDs can both emit and detect light. This means an optical data link can be established with only a single LED at each end, since separate transmitting and receiving LEDs aren’t needed.

The article does mention some drawbacks to using LEDs in this type of application.

  • LEDs are not as sensitive to light as most silicon photodiodes.

  • LEDs are sensitive to temperature. This can pose a problem for outdoor sensors. One solution is to mount a temperature sensor close to the LED so a correction signal can be applied in real time or when the data are processed.

  • Some LEDs I’ve tested do gradually lose their sensitivity.

The author also mentions that amplification of the receiving LED output may be needed since the light sensitive surface is small.

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  • You may also just use a photoresistor or lightsensor. – Paul Oct 14 '17 at 12:11

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