I need to send data over a wireless link, not far - max 50m. I have plenty of laser diodes, 1-5mW, with glass lenses that can be adjusted. I would rather avoid buying a 'receiver', since I can probably build one faster than it can be shipped. I understand that LEDs can generate a few microamps when hit with a weak laser beam. What's the best colour LED for this? And what's the best way to build a minimal amplifier? I would prefer not using an op-amp.

My MCU responds to 3V3 and 5V, though I can probably make use of 1-2V as well.

Thanks in advance.

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    \$\begingroup\$ That is probably not going to work. Some leds can generate some current, but with those small currents also the capacitance of the led has influence. Try a photodiode. I think the lower colors are sensitive for that color and for higher colors. Blue is sensitive for blue. Red is sensitive for Red, Green, Blue. \$\endgroup\$ – Jot Jun 10 '17 at 2:07
  • \$\begingroup\$ @Jot Will do. Post it as an answer please. \$\endgroup\$ – user2497 Jun 10 '17 at 2:09
  • \$\begingroup\$ Any transceiver design MUST include specs for data rate, BER error rate, line of site, beam angle and wavelength then sensitivity in terms of uA/uW of signal after Friss Loss calculations ( inverse square loss) Then understand you need high gain and high impedance to receive low current which with a diode that has self capacitance results in an RC = 0.35/f slew rate limit, thus forcing you to consider a video amp or high GBW TIA amp configuration. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 10 '17 at 2:18
  • \$\begingroup\$ It's just output from a serial port at 9600 baud, amplified with a 2N3904 NPN. Known to work fine, even up to 115200 baud with a proper design. Can't use cable for this. \$\endgroup\$ – user2497 Jun 10 '17 at 2:22
  • \$\begingroup\$ I've posted several logarithmic-compression TIA circuits within the last few months. \$\endgroup\$ – analogsystemsrf Jun 10 '17 at 3:18

I think you rather look for photoresistor or phototransistor. It will fit your need more than LED.


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