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I have a project where I need to send a wireless signal to one of several receivers to turn on an LED.

One transmitter, several (many) receivers, each with an LED. The receivers need to have low power consumption.

Transmitter side:

  • Raspberry pi
  • HT12E encoder
  • 433 mhz transmitter

Receiver side:

  • 433 mhz receiver
  • HT12D decoder

Each individual receiver would have a unique, fixed address.

I was hoping I could use the raspberry pi to dynamically set the address of the encoder to match the relevant receiver, but I cannot figure out if this is possible. The address of the HT12 is adjusted by connecting Ax pins to ground. Can I do this with

Is there a better alternative to this? Can I use the Raspberry to simulate the signal from the encoder? The system must be possible because it is similar to restaurant pagers

This is how I am envisioning it now. Is my understanding correct? Does the address on the transmitter side match with the address on the receiver side?

enter image description here

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  • \$\begingroup\$ Is there a better alternative to this? - yes but define what "better" means. Can I use the Raspberry to simulate the signal from the encoder? - almost certainly with the odd extra part or interface. \$\endgroup\$ – Andy aka Mar 4 '20 at 10:58
  • \$\begingroup\$ I use better and not a more specific definition because I am in search of a good approach to handling the problem defined. Maybe a solution I haven't thought of or don't know about. How would you build a restaurant pager system with the Raspberry Pi? One transmitter sending to a specified receiver out of many. The receiver side should light an LED. Receiver side should be cheap (say 10 USD) in components and have low power consumption and the system should be stable. \$\endgroup\$ – Hjalte Mar 5 '20 at 11:06
  • \$\begingroup\$ Well, I did build one back in the day of the Psion organizer (1990s) so I can't help you with the raspberry pi. It could be used by the server to take orders too. \$\endgroup\$ – Andy aka Mar 5 '20 at 11:08
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You can use the GPIO pins on the Pi to set the address and the data to send.

The HT12E uses 8 address and 4 address/data pins to select the address and data. You'll need 12 GPIO pins from the Pi to drive the data and address pins. The Pi has 25 GPIO pins, so that's covered.

The Pi operates on 3.3V. If you power the HT12E from 3.3V, then you'll have no problems with digital signal levels.

You'll need an additional GPIO pin to drive the /TE pin (transmit enable.)

Entirely possible with a standard Pi and a bit of software.

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  • \$\begingroup\$ Thank you very much for this, @JRE. I think I have sufficient experience on the programming part to implement the solution, and the way you describe it is exactly what I wanted, but what do I set the GPIO pins to to actually deactivate/activate an address pin on the HT12E? As I understand it, a pin is not activated when it is untouched, but is activated when it is connected to ground? \$\endgroup\$ – Hjalte Mar 4 '20 at 17:12
  • \$\begingroup\$ Set a GPIO to low. Take the addresses. Set the address on a receiver by setting some of the address pins low. Transmit to it by setting the same pins low with your Pi GPIO pins. \$\endgroup\$ – JRE Mar 4 '20 at 17:20
  • \$\begingroup\$ Just to make sure, that I understand this, here's an example. Is this the same address: Transmitter side: All address pins connected to GPIOs. A2 and A3 set to low, the rest set to high(?) Receiver side: A2 and A3 connected to ground, the rest left untouched(?). \$\endgroup\$ – Hjalte Mar 4 '20 at 17:27
  • \$\begingroup\$ Yep. That's it. \$\endgroup\$ – JRE Mar 4 '20 at 18:34
  • \$\begingroup\$ Okay, great! And there's no problem in sending current into all the address pins that are not set to low? \$\endgroup\$ – Hjalte Mar 5 '20 at 8:15

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