RF Device (Transmitter and Receiver)

[waQ]

Hello,
I need a device, transmitter and receiver (short range)
I don't really care about the transmitter, but i need a specific receiver.

the receiver have this kind of features:
when it goes out of range from the transmitter signal..it will produce a sound/light/anything..but it need to trigger something..

if you have this kind of device, i would really like to buy it..asap
thank you. your reply may save my day~

[waiweng83]

Do you need to send data from the Tx to Rx? Or you just want to trigger something when the Rx is out of range?

[sushi]

Do you need to send data from the Tx to Rx? Or you just want to trigger something when the Rx is out of range?

if i only need to trigger the speaker when the Tx is out of range? What component should I get? And how do I set the desired range for me to trigger the speaker?

[shahrul]

If you transmit UART on transmitter, then you can receive UART on receiver.
Ex, you transmit UART every 1ms, then you receive UART every 1ms. If not receive UART more than 1ms, it's considered out of range or no signal receive.

[sushi]

If you transmit UART on transmitter, then you can receive UART on receiver.
Ex, you transmit UART every 1ms, then you receive UART every 1ms. If not receive UART more than 1ms, it's considered out of range or no signal receive.

I still cant get your idea.
My project idea is like to track on an item or person. If the item is 10m away from me, the alarm will ring.
What I initially think of is to use RF transmitter 315Mhz and receiver 315Hz. What's more component I need?

[yonghui]

hi,

like wat mentioned by sharul, the transmistter need to continuosly transmitting something to the receiver, if suddenly the receiver did not receiver anything for very long time, the the controller on receiver will do some thing to one the speaker to give out some sound.

[sushi]

hi,

like wat mentioned by sharul, the transmistter need to continuosly transmitting something to the receiver, if suddenly the receiver did not receiver anything for very long time, the the controller on receiver will do some thing to one the speaker to give out some sound.

oo, but how do I set the distance so that at certain distance, the receiver will no longer receive the signal transmitted?

[yonghui]

hi,

im not sure is there anyway to get info of signal strength of low cost wireless, but the simplest way will be, until the signal lost.
low cost wireless, the distance it can transmit is not very far, i think within few meter range only. once the signal lost, the signal transmitted by transmiter is no longer receive by the receiver. so when the receiver didnt receive any signal in certain amount of time predefined, the receiver will need to action to give alarm sound.



rgds,
yh

[sushi]

o, thank you. If I really need a specific range, let's say 5m, then the low cost Tx and Rx cannot provide me tat range, what shall I look for? rebuild the Tx and Rx myself? any other good suggestion?

[aurora]

Hmm... you must be designing some sort of dog collar, or child monitor; or a monitoring device that is attached on something that is very mobile (and unpredictable)?

All wireless device transmit using electromagnetic radiation, aka lightspeed; and it's too fast for a uC/PC to detect the difference and tell the distance from transmit to receive. For distance, we use soundwave; and so we have ultrasonic sensor, and several other type of proximity sensor. The disadvantages of using soundwave is that it require line of sight.

Sensors are nothing more than just a device that detect physical properties. You need to figure out and decide what kind of properties you want detect, and your tolerance for such sensor. There is nothing perfect (yet), so there are bound to be some error here and there.