Electronic – Simplest remote IR

infraredwireless

What I need is: when I turn on a IR led, a receiver circuit in the other side would have 5V or 0V depending on the state of the transmitter. Simple.

I have a IR transmitter and a photo-diode for receive, those used on every IR control and receiver. I don't know how the photo-diode works so how should the circuit be? Should I use a transistor configured in saturation / cut-off working with the receiver?

Feel free to recommend me. Thanks

Best Answer

Phototransistor configured as an inverter:

5V ----+
       |
       /
       \  47k
       / 
       |
       +----- Logic output (inverted)
       |
  \   /
  \  |    NPN
      \>  Phototransistor
       |
      ---
       -

A phototransistor is like a photodiode, but has a significantly increased gain. So when light shines on it (or IR, if it has an IR filter) it will pull down the output, conducting a few mA. A photodiode could do the same job, but you'd need a much greater (x100-1000) resistor, and this might be overwhelmed by the any load impedance.

You could put another inverter on the output to get a logic signal of the correct polarity (or to buffer it, as it won't take much load current.) Here is one possible inverter circuit:

          5V ----+
                 |
                 /
                 \  10k
                 / 
                 |
                 +--- output
                 |
          10k   /
Input ---/\/\/--|   NPN
                \>  2N3904
                 |
                ---
                 -

Related Solutions

Electronic – arduino – Virtual Wire Control

Unless I misunderstood the question, it should be as simple as extending the code where you print out what's in the buffer with some if-then statements. For example your code:

for (i = 0; i < buflen; i++)
{
    Serial.print(buf[i], HEX);
    Serial.print(" ");
}

goes through the received string and prints it out bit by bit. If, instead, you want to know if you received an "A", you can use:

if (buf[0] = "A")
{
  //flip bits here
}

You could also use a Case-Switch block to define several letters. There are many ways to improve this code, including using strcmp so that you can send full words and not worry about case or terminations, but it's best to worry about that once you're off the ground.

If I misunderstood the question, I apologize. I'll be glad to try again with more information.

Electronic – How does temperature affect wireless transmission

Temperature isn't going to matter to the antenna or the RF field it creates. The issue is most likely with your circuit or what is powering it. Are all components you are using rated for under 0C operation? Some are only 0-70C, although going down to -20C is fairly common. Don't assume. Check all the datasheets.

The most likely problem is the battery if that's what you're using to power this unit. Both output voltage and capacity drop with temperature for most batteries. What kind of battery are you using? What voltage range does your circuit need? Are your batteries fresh or fully charged?

You may have to rethink your power supply to be able to run from a lower battery voltage than anticipated.

Added:

One other possibility occurred to me, especially since you say everything is running from a 12V battery and you are only using 8V and 3.3V. A bad solder joint can work at some temperatures then fail at others as the metal expands or contracts. If this is a small device, try reflowing all the solder joints and see if that changes anything. Preferably add a tiny bit of solder to every joint, but definitely make sure the solder gets molten for a second or so at least. Then check each joint with a jeweler's loupe and redo anything that looks suspect.

Let us know if this changes anything.

Best Answer

Related Solutions

Electronic – arduino – Virtual Wire Control

Electronic – How does temperature affect wireless transmission

Added:

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