HT-12d decoder

Thread Starter

denison

Joined Oct 13, 2018
328
Hi, I am using the decoder in a RF project. I am transmitting temp readings from a remote location. All works ok until transmitter turned off. Then decoder continues to show the old temp readings.
The data sheet states that if no transmission should be a low on the data pins. I have tried dragging down the pins to a low with 10k resistor connected to ground. Doesn't work.
If I turn off power to the decoder and power up again I get the lows at the decoder data pins. This is not the solution I want as the receiver will be in a remote location.
I am using the arduino nano boards for encoder and decoder. Anybody got a fix for this?
Please note this is not a cross thread as my previous post covered the encoder ht-12e.
 

DickCappels

Joined Aug 21, 2008
10,152
Can you put the controller in charge of interpreting the temperature data from the decoder and then setting it to zero when the transmitter turns off? (f it has a way to tell when the transmitter turns off).
 

Thread Starter

denison

Joined Oct 13, 2018
328
Hi Dick, When transmitting the receiver shows a blinking led. No transmission and the led is off. The problem is the blinking led. If it was continuous on and continuous off no problem.
Several possible solutions. Using Arduino millis program for timing the off period. If it is off for more than 5 seconds then the receiver knows transmission has stopped.
Another possible solution is for the transmitter to send an off data message just before turning off power on the transmitter.
The ht12d retains the last transmission of data on its data pins. So if the last transmission was say for 20c the data pins show the code for that even when the transmission has stopped.
 

Ya’akov

Joined Jan 27, 2019
9,071
Can you send an end of transmission code before taking shutting down the transmitter? That way it would be clear the last thing sent was not a current valid temperature. Possibly a timestamp would simplify it further.
 

Thread Starter

denison

Joined Oct 13, 2018
328
Can you put the controller in charge of interpreting the temperature data from the decoder and then setting it to zero when the transmitter turns off? (f it has a way to tell when the transmitter turns off).
Thanks for your interest Dick. Problem solved now. From the transmitter before shut down of transmitter I send data 0000 to the decoder. This is latched by the decoder and held at the decoder even after transmitter shut down. This tells the microcontroller it can shut down all control it has over external devices. I guess you can't tell the microcontroller to shut down its own power source. That would be like suicide for it. It would save power at that end although the standbye power is probably negligible.
 
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