Looking for help to create a simple multiple (up to 4) 433Mhz transmitters to one receiver

Thread Starter

smduke

Joined Feb 8, 2018
8
Hello,

I am trying to create a simple multiple (up to 4) transmitters to one receiver. a 433mhz transmitter receiver is what I would like to use. I need this to transmit to a lcd and tell me what transmitter is the one transmitting on the lcd. as far as the transmitter goes I would like to have it transmit when a magnet switch is tripped. can this be done? I am not a programmer and to be honest I am very new at this. I would be willing to pay for someone to set this up for me, is anyone interested in doing this for pay?

thanks you
 

LesJones

Joined Jan 8, 2017
2,643
If more than one transmits on the same frequency at the same time you will just receive rubbish. If you do something to ensure that only one transmitter is transmitting at a time there is no problem. There is no problem using a magnet and reed switch to switch a transmitter on. You could just add a letter or number to the transmitted data to identify the transmitter.

Les.
 

Thread Starter

smduke

Joined Feb 8, 2018
8
would someone be able to draw me up some plans for this and I could put it together. another issue I am going to run into is programming it would someone be able to lend a hand in the programming. I have all the components as far as the transmitter, receiver and 2 Arduino uno boards.
 

WBahn

Joined Mar 31, 2012
25,784
How do you plan to deal with the collision issue that LesJones mentioned?

Is there a receiver at each transmitter than can be listening to determine if it is okay to transmit?

If so, is each transmitter situated where it can hear all of the other transmitters?

How long will each transmitter transmit? Just once each time it is triggered? Or continuously as long as the trigger condition exists?
 

Thread Starter

smduke

Joined Feb 8, 2018
8
so how I would like this to work is the transmitter is tripped via the reed switch, sends signal to the receiver's lcd display telling me if it is #1,#2,#3 and so on. there should not be multiples going off at once but is possible. so as soon as it receives power from the reed switch it would transmit.
 

LesJones

Joined Jan 8, 2017
2,643
What is the nature of the transmitted data ? Will adding the transmitter identification to the data stream cause you a problem ? If you used HC-12 moules which can be set to a number of channels in the region of 433 Mhz you could have the remote transmitters on 4 different channels and have 4 receivers with their data outputs combined to feed your data logging computer. The HC-12 modules have both a receiver and transmitter on the module. thy work with serial data up to 115200 bauds. Telling us exactly what you are trying to achieve would help us to give suggestions that would fit your application.

Les.
 

Thread Starter

smduke

Joined Feb 8, 2018
8
ok, I apologize for not describing this clearly. I have attached a file on what I am trying to achieve. I would also need a buzzer go off at the receiver location when a transmitter is transmitting. this is for ice fishing in Minnesota, I will have 4 outside lines then when I am inside my shelter I will know when a fish takes my bait on one of the outside lines and I will know what one is being taken by a fish.
 

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LesJones

Joined Jan 8, 2017
2,643
As you are planning to use an LCD display I assumned the remote transmitters were sending some data (Such as temperature readings) back to the receiver so I thought it would be easy just adding some address information to the data. I imagine as your reqirement is so simple you will be using the very cheap transmitter and receiver units. As far as I know they are all on the same frequency so my suggestion of usiing different frequencies near 433 Mhz is not an option. The HC-12 modules are more expensive and would require extra electronics to cause them to send out some data. (0nly one byte would need to be sent) This could be done with an 8 pin microcontroller (Such as a PIC12F1840 or an ATtiny13) but you would need to program them. It could be done with a few digital ICs but that would involve more time building the circuits. I think at the receiving end it would be simpler just to use 4 LEDs rather than an LCD display. I cant think of a cost effective way to solve your problem at the moment.

Les.
 

WBahn

Joined Mar 31, 2012
25,784
ok, I apologize for not describing this clearly. I have attached a file on what I am trying to achieve. I would also need a buzzer go off at the receiver location when a transmitter is transmitting. this is for ice fishing in Minnesota, I will have 4 outside lines then when I am inside my shelter I will know when a fish takes my bait on one of the outside lines and I will know what one is being taken by a fish.
How far away from the lines is the shelter? Would you be able to hear a buzzer that was at the line? If so, then just make four switch/buzzer/light systems and put one at each station. You hear a buzzer, you step out and look to see which station has the light on.

It seems like this somewhat defeats the purpose of ice fishing -- if you want to automate it so that you can stay nice and warm until it's time to collect your fish, why not just buy the fish at the supermarket?
 

Thread Starter

smduke

Joined Feb 8, 2018
8
How far away from the lines is the shelter? Would you be able to hear a buzzer that was at the line? If so, then just make four switch/buzzer/light systems and put one at each station. You hear a buzzer, you step out and look to see which station has the light on.

It seems like this somewhat defeats the purpose of ice fishing -- if you want to automate it so that you can stay nice and warm until it's time to collect your fish, why not just buy the fish at the supermarket?
An outside buzzer will not work, I currently have that made. Since the reel can be up to 200 ft away I would want to transmit it. As far as buying fish at a market, what fun is that?
 

WBahn

Joined Mar 31, 2012
25,784
An outside buzzer will not work, I currently have that made. Since the reel can be up to 200 ft away I would want to transmit it. As far as buying fish at a market, what fun is that?
How often do you expect a fish to be on more than one line at the same time?

Perhaps more to the point, what is the acceptable outcome if and when this happens?

If you are not careful, then you risk the signals jamming each other and getting no indication at the receiver. If two fish at once is a jump for joy type situation, it would be a shame to miss out on it.

Here's one simple way to deal with it.

Have each transmitter modulate the signal at a different frequency -- so maybe 100 Hz, 200 Hz, and 300 Hz (perhaps three frequencies that aren't harmonically related would be better). Then have each transmitter transmit transmit the signal with a 10% to 25% duty cycle but make the periods different. Essentially each one "chirps" at a different rate. Perhaps #1 chirps 10 ms on and 30 ms off, #2 chirps 10 ms on and 50 ms off, and #3 chirps 10 ms on and 70 ms off. Once the transmitter is triggered, it either chirps for a set amount of time, until the triggering event goes away (probably along with the fish), or someone gets over there and resets it -- whatever makes the most sense to you. In the mean time, even if all three transmitters are going simultaneously, the receiver will be getting clear chirps from all of them at least once every couple hundred milliseconds. The display can then indicated that it heard a chirp from a given transmitter within the last 500 ms by every time a clean chirp is heard a timer is reset the display for that receiver is only extinguished if the timer expires. With a microcontroller that would be easy, but it shouldn't be too hard even with discrete logic.
 
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