RF remote control for relay
Hi,
Please note that when building RF circuits, their diagrams themselves won't help too much. How to assemble their components on a PCB and adjusting them properly forms the crucial step in an RF project.
Usually the RF modules (may be called RF heads) for transmit (TX) and receive (RX) are produced as low-cost products for general use. The simplest two types are one for raw data ( 0 and 1) and the type that includes a pair of encoder/decoder (in TX and RX respectively).
The RF module of raw data type has only 3 pins; Vcc, ground and data (data input if TX and data output if RX).
This type is rather small and very low cost if the range is about 100m.
Lately I used it to upload new texts (as binary data) on my 1-line LED moving message signs (produced for the local market to display Arabic/English messages). But since these modules are very simple, an MCU, at each side (TX and RX) is usually needed to send/receive the data in well defined protocol (number of bits in each data packet and their timing). I usually decide the protocol on my own (very simple or very complex depending on the application).
In your case, it seems you need just 4 on/off keys. When I first worked with RF and needed also a few on/off keys, I just bought a car alarm and took from it the RF parts. As you know, the simplest car lock/alarm has a nice small RF remote unit (perhaps two). On the receiver board, one can easily find out the 4 outputs which are activated (low or high) when its corresponding TX key is pressed. The rest of the receiver board can be disregarded.
Good luck,
Kerim
thanks kerim 4 d enlightenment, you see i chose this project bcos i want to have a better understanding of RF remote control.
with respect to d project,
1, can i build d control of both RX and TX with common components or extract from say car alarm
2, can i get a working circuit diagram.
dis is really important to me and i will apreciate if u can help.
tnks
Hi,
I wished I can help you in the RF field (here the standard bands are around 315 MHz or 433 MHz for example). Since many decades, I try not re-inventing the wheel when it is available. On the other hand, I did, in the far past and at just a couple of times, build RF links for my personal use only, hence based on modulation/demodulation methods on my own (for privacy). The circuits were rather complex and primitives at the same time hence far from being perfect, though I let them work the way I want. I never tried producing the small RF heads (modules) that may be needed in my products (for sale). I was interested instead in the ways by which I can send data via their RF link only so I got them ready-made.
Naturally, if you are now a student taking a course on RF communications, you have no choice but to design/analyze an RF circuit then simulate it before building it as a real circuit. In this case, the circuit is already defined by some given data as frequency, bandwidth, supplies, modulation method... etc.
Kerim