Arduino 433MHz transmission fails if falling edge is less than 122ms

Question

I am trying to control a LED using a high-power 433MHz transmitter receiver pair, with transmitter connected to my Arduino Nano.

Here is the transmitter (XLPCF20): http://www.colorapples.com/rf-wireless-transmitter-module-315-or-43392mhz-xlpcf20-p-38493.html

Here is the receiver (CDR 5 B): http://www.amazon.co.uk/433MHZ-115dbm-Wireless-Receiver-CDR-5-B/dp/B00COD96UG

I can send HIGH to a data channel at the transmitter (it has 4 channels) and receive the HIGH input at the same channel at the receiver, successfully lighting up a LED. This is my current test sketch:

void setup(){
  pinMode(8, OUTPUT);
}

void loop(){
  digitalWrite(8, HIGH);
  delay(122); //this is the important line
  digitalWrite(8, LOW);
  delay(100);
}

This works well, however, if I change the 122ms delay at the falling edge to 121ms (or anything below that) I have no output at the receiver. The LED doesn't light at all. It's the same for all channels, there's a sharp change at that very border between 121ms and 122ms (found the exact value by trial and error). At the transmitter/Arduino, the output signal is clear so it's an error with the transmitter or receiver. I've used other, much simpler/cheaper 433MHz transmitter/receiver pairs in the past with no such issue. At the rising edge (second delay call, the one with 100ms), there's another issue when I drop below 13ms. At exactly 12ms, the LED is unstable, it sometimes blinks as expected, but sometimes just lights up. Anything below 12ms, the LED is constantly high, not a single blink.

UPDATE: If I use _delay_ms instead of regular delay, I get about 1ms more room for both edges, but below that, it's still the same.

UPDATE 2: I've tried changing to different output pins on my Nano, both PWM and non-PWM ones. Nothing changes.

What would be the problem?

Answer 1

You need a bare transmitter and receiver pair with one channel. Photo is super regenerative receiver. You can use superhetrodyne type for better anti interference. Generally, these works up to a few kHz switching, put Hi in tx and Hi come out at Rx.

The one you got has additional encoder MCU. It read 4 key lines, wait 120ms for key debounce, so shorter input are ignored. It then send a coded message to the receiver where another MCU decode the message and send out hi /lo on 4 channels.

Your module is generally used inside these 4 key remote control (car door opener, etc.) Note more pin, as out1 to out4. The bare is out1 only.