Hi

I need to switch on three circuits wirelessly (within 2 meters) when received three different signals from the corresponding transmitter(s). While doing a search on the net, I came across the Tx/Rx modules such as shown below:


These modules can easily do the job, but unfortunately these are not available in my country because banned to import.
Therefore, I am looking for some alternate. I was wondering if it is possible to transmit a signal using a crystal oscillator using FM transmitter and then receiving that with an FM receiver and somehow convert to high output? When the transmitter stops transmission, the output at the receiver goes low. If yes, would it be possible to transmit/receive 3 different frequency tones simultaneously?

 

I suspect the reason these modules are not allowed into your country is they are on a frequency allocated for some other purpose. If you build a transmitter yourself it will have to be on a frequency that has been allocated for the type of use that you want to use it for. You would probably also have to get type approval which would be expensive. Have you considered using modulated infra red ?

Les.

 

I suspect the reason these modules are not allowed into your country is they are on a frequency allocated for some other purpose. If you build a transmitter yourself it will have to be on a frequency that has been allocated for the type of use that you want to use it for. You would probably also have to get type approval which would be expensive. Have you considered using modulated infra red ?

Les.

Well, I don't know exactly why those modules are banned in my country.
As far as my requirement is concerned, it's transmitting radius is only 2 meters. Short range transmitters are not banned here, otherwise the wireless mikes would also have been illegal to use.
IR transmission is not suitable for project.

 

Too bad, IR would have been fairly easy.

FM can do it. Send a tone burst via FM.

Here is one way:

At the transmitter the tone bursts can have three different durations (in time), one durations for each of the three outputs.

At the receiver the tones is detected, with a diode detector or similar and converted to digital pulses with a compariter. Simple digital circuits indicate when particular durations are received.

It might be easier to use remote control encoder and decoder chips, such as these trc1315.

 

At the transmitter the tone bursts can have three different durations (in time), one durations for each of the three outputs.

At the receiver the tones is detected, with a diode detector or similar and converted to digital pulses with a compariter. Simple digital circuits indicate when particular durations are received.

It might be easier to use remote control encoder and decoder chips, such as these trc1315.

Thanks for your input, Dick.

What I understand, example:
Job A => Tone 2.1KHz for 2 sec
Job B => Tone 2.1KHz for 3 sec
Job C => Tone 2.1KHz for 4 sec

If I understood correctly, then it is not suitable for my application because:
a) duration of each job depends upon the length of the signal received at the input of the transmitter.
b) if more than one jobs are to be performed simultaneously, how they will be detected and separated at the receiver?

 

Are the three switches for the three circuits, located at one location? Do you need just one receiver?

Are there three separate transmitters? Does more than one transmitter transmit at the same time?

Why not IR? Is there a barrier between transmitters and receiver?

Give us more details of your setup.

 

Are the three switches for the three circuits, located at one location? Do you need just one receiver?

Are there three separate transmitters? Does more than one transmitter transmit at the same time?

Why not IR? Is there a barrier between transmitters and receiver?

Give us more details of your setup.

Well, I am trying to modify a bike helmet in such a way that:
a) when the bike's brakes are applied, a strip of red LEDs will light up behind the helmet.
b) when either of the turn indicator is activated, the corresponding orange LEDs will light up behind the helmet.
The transmitter(s) will be installed on the bike and the receiver(s) to be installed in the helmet.

The brake lamp and both the indicator lamps will be the three separate triggering signals.
1) Brake signal: Duration not fixed, can activate alone or with either of the indicator signal.
2) RH turn signal: Duration not fixed, can activate alone or with brake signal.
3) LH turn signal: Duration not fixed, can activate alone or with brake signal.

Since the position of the helmet is not stable, IR cannot be used. The working range is less than 2 meters.

 

That would be ok . . . if you don't turn or lean your head. I suggest mounting your signal lights on a stable part of the vehicle. Such as under/behind seat or on fender.

What happens when the traffic light changes and you have to climb on the brakes, and then you notice a pretty lady on your right? Will all the drivers behind you, be able to see your brake lights? While you are gawking at that lady?

I don't think that would be legal here.......I think the lights have to be on the vehicle.

Are you mountain bike riding?

 

Well that is pretty much clear that the original brake lamp and the signal lamps are not tempered or removed. What I am trying to make would be a fancy gadget.

 

I;m not advocating this http://www.ebay.com/itm/Multi-Frequ...-Duplicator-433-868-315-418-MHz-/111530469258, but I want to illustrate something. There is a 300 MHz and a 400 MHz band that's allocated to stuff like garage door openers, but not all countries allow both frequency bands. There is the universal ISM bands that can any kind of garbage on it. One special frequency, is 13.56 MHz. There is one at where microwave ovens operate and some in the various frequency ranges.

That may be your problem.

 

Brake lights and turn signals -this requires a rethink.

I personally have not used bluetooth modules but suspect that is a good solution, provided you can do some programming.

 

Personally, I am thinking to start with only one channel i.e. with Brake Light set-up.
My idea is to transmit a tone like 2.1KHz using an FM transmitter.
Receive the same with a small basic FM receiver and then somehow convert it into high state to switch on 5 LEDs.
But I could not figure out how to convert the received signal into high state. Any suggestions?

If this set-up of one transmitter+receiver+converter will work then I could simply make two more for the turn signals, though three receivers+converters would be quite bulky to install on the helmet.

 

One reason the products are banned may be because of the International Traffic in Arms Regulations (ITAR) that control the export and import of defense-related articles and services on the United States Munitions List (USML). While not munitions themselves the devices could be modified or use to modify a weapon. I only mention this as I am retired compliance advisor and even discussing how to build a similar device with a citizen of a ITAR banned country will have the State Department knocking on your door. If you have questions you can look up most at https://www.pmddtc.state.gov/regulations_laws/itar.html
I mention this as some of the people I worked with answered emails unknowingly violating ITAR. Just a heads up.

 

Are you opposed to using a microcomputer! Have you ever coded?

TRANSMITTER
Three separate inputs. One Bluetooth transmitter. Send a 1, 2, or 4 via Bluetooth. Or any combination thereof. If 4 was the brake and 2 was the left turn, sending a 6 means you are braking and about to turn left.

RECEIVER
Received number and sets microcontroller outputs accordingly. Your code can control the LEDs any way you want.

I'm familiar with the Arduino product line and their programming. I would use a Trinket.

 

Are you opposed to using a microcomputer! Have you ever coded?

I have very basic knowledge of microcontroller programming that's why I prefer doing without it.

 

After some browsing I found these two simple working circuits of Transmitter & Receiver.
TRANSMITTER


RECEIVER


They can be used for switching only one circuit. I was wondering that if two more carrier waves and input signals are introduced (of course with different frequencies) in the Tx, and we have 3 Receivers with matching tank circuits; can the 3 receivers share a common antenna? Here is my proposed modification in the Rx:


A, B & C can have variable capacitors to tune the carrier frequencies.
The red LED is for indication, that the Rx is ON.