So I’m constructing an RF link alarm for a Receiver RWS-434 and Transmitter TWS-434 with encoder and decoder. I have a sound buzzer along with a NAND gate at the Receiver side that sounds when not within range. My problem is that the sound is not very consistent. In other words, when I am approaching the cut-off range it gives short intermittent beeps and then finally it sounds once I’m completely away until you get back within range. I’d like it to sound once I reach the cut-off range without doing those stupid intermittent beeps like if it’s still picking it up the signal slightly. Can anyone help me find a solution for this?
Maybe add a timer (555 chip) to ensure that the receive signal is present or absent for more than a preset time.
That sounds great but what if I want it to immediately stop once I get back in range. Isn’t the 555 timed only? So even if I’m back in range it’ll still be sounding until the end of the set interval?
Depends on how you set it up.
When the signal is detected the 555 timer is reset. Then when a signal drops out the 555 timer starts and if the signal hasn’t been detected when the 555 times out the alarm is tripped.
Any signal detection resets the 555 and kills the alarm.
You may need a couple of logic chips as well.
Another way is use a 12F508 PIC and program to timing and logic in the PIC.
or, arguably better, this
your recevier does not have a RSSI output. Otherwise you could have connected it to a microcontroller and then programmed the micro to average out the RSSI reading to get a more smooth feeling of the range and then trigger on it.
The Range is a “grey area” with RF comms