Multiple RF transmittal without arduino

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
I know this is a very simple process for all you electrical gurus. Unfortunately I'm not 100% electronically inclined so I'm stuck on a simple project.
How would I connect multiple 433mhz transmitters that have learn capability to a single receiver and have the receiver illuminate a separate led light when each individual transmitter that it has been linked to is triggered? I'd prefer it if I didn't have to use arduino as there is very limited electricity plus it must remain very small and there is no wifi. Thanks!!
 

KeithWalker

Joined Jul 10, 2017
1,778
I know this is a very simple process for all you electrical gurus. Unfortunately I'm not 100% electronically inclined so I'm stuck on a simple project.
How would I connect multiple 433mhz transmitters that have learn capability to a single receiver and have the receiver illuminate a separate led light when each individual transmitter that it has been linked to is triggered? I'd prefer it if I didn't have to use arduino as there is very limited electricity plus it must remain very small and there is no wifi. Thanks!!
We need more information before we can suggest solutions:
Can more than one transmitter be active at the same time?
Is each led assigned to a specific transmitter?
Is any kind information being sent by the transmitters?
A little more general information on the project would also make it easier.
 

djsfantasi

Joined Apr 11, 2010
7,689
If you got one of these, or similar...
https://www.ebay.com.au/itm/CJR-120...976654?hash=item48d0d0980e:g:hyoAAOSwA3ldX5-C
and 8 remotes, then remove 7 buttons from each remote, just leaving one different button per remote, that may be what you are wanting.
I've not used these myself, so I cannot say if it will really work o not.
But more info will be a help.
And what happens when multiple buttons are pressed? For example, button 1 on remote 1 is pressed at the same time button 2 on remote 2 is pressed. What’s the behavior of the receiver in this case?
 

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
We need more information before we can suggest solutions:
Can more than one transmitter be active at the same time?
Is each led assigned to a specific transmitter?
Is any kind information being sent by the transmitters?
A little more general information on the project would also make it easier.
Thanks for responding Keith.
- Yes multiple transmitters can be active at the same time.

- I'd like it if the receiver had an led that was assigned to each individual transmitter when it was linked to the receiver. This would mean the receiver and transmitters would need to have learning capabilities.

- The only information that will be transmitted to the receiver is when a reed switch is activated on each transmitter.

Thanks again Keith for you response.
 

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
If you got one of these, or similar...
https://www.ebay.com.au/itm/CJR-120...976654?hash=item48d0d0980e:g:hyoAAOSwA3ldX5-C
and 8 remotes, then remove 7 buttons from each remote, just leaving one different button per remote, that may be what you are wanting.
I've not used these myself, so I cannot say if it will really work o not.
But more info will be a help.
Thanks Dendad,
I'll have to look into this and see if it can be modified enough to work or if there may be a solution that may be more straightforward and simple.
 

LesJones

Joined Jan 8, 2017
3,172
The transmitters do not "learn". It is the receivers that learn to recognise the code from the transmitter.
Do you want the LED to come on only when a button is held down, do you want a press of the button to toggle the LED from on to off or do you want two buttons to control each LED (One for on and one for off.) ?
How many channels (LEDs) do you require ?
What range do you need between the transmitter and receiver units ?
What voltage and current does each LED require to drive it ?

Les.
 

KeithWalker

Joined Jul 10, 2017
1,778
Thanks for responding Keith.
- Yes multiple transmitters can be active at the same time.

- I'd like it if the receiver had an led that was assigned to each individual transmitter when it was linked to the receiver. This would mean the receiver and transmitters would need to have learning capabilities.

- The only information that will be transmitted to the receiver is when a reed switch is activated on each transmitter.

Thanks again Keith for you response.
You will need to transmit some kind of information for the receiver to distinguish which one is transmitting.
One of the most simple systems would be for each transmitter to transmit a digital code. Most of the problems that would occur when more than one transmitter is activated can be avoided by only turning on each transmitter long enough to transmit it's identity and a status whenever the reed switch is closed and again when it is opened. There will still be rare occasions when two transmitters are sending at the same time. You will lose that information.
The receiver will not "learn" the received signals. A decoder will read the transmitted code and turn on a LED. If the code includes a status bit, the led can be made to stay on from when closed status is received until the open status is received.
The decoding can all be done using digital logic but it would be much simpler to use a microprocessor.
Another simple system would be to use a different tone to modulate each transmitter. The tones can be detected using active filters. If the frequencies of the tones are selected carefully so that the intermodulation products fall outside of the frequency band that is being used, having two transmitters on at once would not be a problem..
 
Last edited:

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
The transmitters do not "learn". It is the receivers that learn to recognise the code from the transmitter.
Do you want the LED to come on only when a button is held down, do you want a press of the button to toggle the LED from on to off or do you want two buttons to control each LED (One for on and one for off.) ?
How many channels (LEDs) do you require ?
What range do you need between the transmitter and receiver units ?
What voltage and current does each LED require to drive it ?

Les.
Hi Les,
- I only need the LED to turn on when a magnetic reed switch is opened. At that point I want an LED to light up on the receiver for that particular switch.

- 4 possibly 6 channels at the most.

- I only need approximately 10 to 12 feet of range between the transmitters and the receiver.

- I'm honestly not entirely sure yet on the voltage and current for each LED. As little as possible at this point as I'd like for this to be as small as possible. Ideally the receiver would be similar in size to a keyfob.

Thank you
 

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
You will need to transmit some kind of information for the receiver to distinguish which one is transmitting.
One of the most simple systems would be for each transmitter to transmit a digital code. Most of the problems that would occur when more than one transmitter is activated can be avoided by only turning on each transmitter long enough to transmit it's identity and a status whenever the reed switch is closed and again when it is opened. There will still be rare occasions when two transmitters are sending at the same time. You will lose that information.
The receiver will not "learn" the received signals. A decoder will read the transmitted code and turn on a LED. If the code includes a status bit, the led can be made to stay on from when closed status is received until the open status is received.
The decoding can all be done using digital logic but it would be much simpler to use a microprocessor.
Another simple system would be to use a different tone to modulate each transmitter. The tones can be detected using active filters. If the frequencies of the tones are selected carefully so that the intermodulation products fall outside of the frequency band that is being used, having two transmitters on at once would not be a problem..
That is all very useful information Keith. Thank you. One of the things that I'll want to incorporate in the programming is a sleep mode so that when a switch is left open for more than say a minute or so it will not continue to run the battery down.
I'm not very familiar with using tones to differentiate, but that sounds like a very good idea as there could be times when both multiple switches are opened simultaneously.

Thanks again!
 

LesJones

Joined Jan 8, 2017
3,172
One way round the problem of two transmitters transmitting together Would be the "receiver" end to actually be a transceiver. It would transmit 6 different codes in sequence. Each "transmitter" would also be a transceiver. It would only respond to it's code if the button was pressed. Weather this was suitable for you purpose would depend on timing. Telling us exactly what you are trying to achieve would probably help us to suggest a suitable solution.

Les.
 

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
Thanks for all your responses. They are all greatly appreciated!
Ok for proprietary reasons I can't completely explain for what company and the exact design of what we have, but I can in a roundabout way tell you what we have and how it needs to be. This should give you a better idea.
On our transfer trucks we have 6 small doors roughly 1'x1' that will be temporarily opened and closed from the outside by different employees. As we are driving we need to know when each door has been opened and then closed so we can deploy the next "item" so they can open the door and have the next "item" waiting for them. We must have wireless as the chambers that the items are contained in are completely sealed off. There is no way to run wires from the doors to the cab of these vehicles.
We don't want 6 different receivers in the cab either for each door transmitter. Ideally we'd have one receiver that contained 6 or 12 LED lights that would either light up when each door is closed with a single LED if we had 6 LEDs or would light up say green when the door opens and turn red when the door is closed if we had 12 different LEDs.
It would be nice also if the transmitters would go in a sleep mode whenever they are in their respective position for a certain amount of time as to not put excessive wear on the battery by constantly transmitting that the door is either opened or closed.

We're going back and forth on using hall effect sensors instead of reed switches as some of areas we go in have some very rough terrain and reed switches have moving parts where hall effect sensors do not. Not sure how much wear and tear reed sensors can hold up to.
We're also considering using the atmega328 microcontroller for this setup.

I hope that this helps in understanding what we are trying to accomplish here.

Thanks again for all your expertise!!
 

LesJones

Joined Jan 8, 2017
3,172
While thinking about a way to implement the method I suggested in post #11 made me think of using HC-12 modules. It then occurred to me that these can be set to a number of channels that fall within the 433 Mhz band. The RF transceiver chip (44631b) used on the HC-12 module could be used to transmit on 6 different channels so they would not interfere with each other. The simple solution for the receiving end would be to use 6 of the 44621B chips but as you insist on a single receiver here is a suggestion for designing the receiver. The first stage would be an RF amplifier with enough bandwidth to cover all 6 channels. This would would be followed by 6 mixers each with a local oscillator that would mix down to an IF frequency (Say 10.7 Mhz) The output of the detector on the output of each IF amplifier would indicate reception of one of the transmitters and this drive an LED.
I don't know if you would consider to meet your requirement for a single receiver. If I was doing it I would use a HC-12 module with a small microcontroller (Such as a PIC12F1840 or ATtiny13A) But you could design your own board around a 44631b chip or reprogram the STM8S microcontroller on a HC-12 module for it to control the 44631B chip to do what you want.
 

Thread Starter

Tomsalwayssmilin

Joined Nov 19, 2019
7
While thinking about a way to implement the method I suggested in post #11 made me think of using HC-12 modules. It then occurred to me that these can be set to a number of channels that fall within the 433 Mhz band. The RF transceiver chip (44631b) used on the HC-12 module could be used to transmit on 6 different channels so they would not interfere with each other. The simple solution for the receiving end would be to use 6 of the 44621B chips but as you insist on a single receiver here is a suggestion for designing the receiver. The first stage would be an RF amplifier with enough bandwidth to cover all 6 channels. This would would be followed by 6 mixers each with a local oscillator that would mix down to an IF frequency (Say 10.7 Mhz) The output of the detector on the output of each IF amplifier would indicate reception of one of the transmitters and this drive an LED.
I don't know if you would consider to meet your requirement for a single receiver. If I was doing it I would use a HC-12 module with a small microcontroller (Such as a PIC12F1840 or ATtiny13A) But you could design your own board around a 44631b chip or reprogram the STM8S microcontroller on a HC-12 module for it to control the 44631B chip to do what you want.
Thank you Les. I'm definitely going to look at these options and see what I can configure. I think this is definitely on the right track though.
Thanks again for all the wonderful feedback. I'm sure that something can be created now with these suggestions.
 
Top