parallel data transmission possible or not?

hi all,
i have a rf 434 transmitter ic..which is capable to accepting serial input signals with a maximum speed of 1 kbps and transmitting it via rf to the reciever.
so my doubt is is it possible to transmitt 4 pwm signals at the same time using this transmitter...

similarly at the reciever i need the same 4 pwm signals at output.
please reply.it is for my mini project.
thanks

not with the transmitter you have mentioned......

ckshivaram said:

not with the transmitter you have mentioned......

Click to expand...

ok thanks ckshivram.
i only want to transmit the 6 pwm signals via rf and recieve them at a distance of 100 meters..
which transmitter should i use.shall i use the 2.4 ghz transciever. but i dont know the ckt.please help.

hi please help.
i want a 8 bit parallel transmitter.
the transmitter should be able to take 8 inputs each of 100 hz and transmitt it via rf to the reciever..the reciever should give out the same 8 bits..
please help..i need it for my mini project.the circuit doesnt matter.please give few details about the ckt..i will make it by myself..but which is the transmitter and reciever required and which is the encoder and decoder needed....any body please reply
thanks

I don't exactly understand you're specification. If a pwm signal with a period of 100 Hz is transmitted once per cycle, you get at best on or off state, but no pwm (pulse width modulation). You can transmit a 50 Hz squarewave (alternating on and off). You can assemble individual bits to a serial data stream by a shift register, but an unequivocal frame synchronisation must be added. So the resulting data rate will be somewhat higher than 1 kbps. And you have to consider the requirement of RF modules for balanced serial data. Manchester encoding could be used, but doubles the effective data rate.

In most cases, a microprocessor would be the lowest part count solution, but unfortunately requires programming.

P.S.: Perhaps you can give an example, what kind of information is carried by the "pwm" channels.

https://www.kitsrus.com/pdf/k175.pdf these are parallel rf transmitters.. hope this is helpful for you

thanks but i wanted to make one like the one showed in the above pdf file...parallel rf transmitter..
do any one know the microcontroller code..and is it possible for me to send pwm signals as inputs .if yes than what is the max safe frequency of the pwm signals

the pwm signals actually carry the analog voltage when demodulated...
my actual requirement is to transmit and receiver 8 voltage levels(analog voltage dc voltages))) these voltages could vary between 0 volts and 5 volts...
so i thought of using pwm and then transmitting digital data..
does any one know any other better way to do this project of transmitting 8 analog dc signals..

which pdf are you talking ... can you be more clear

FvM said:

I don't exactly understand you're specification. If a pwm signal with a period of 100 Hz is transmitted once per cycle, you get at best on or off state, but no pwm (pulse width modulation). You can transmit a 50 Hz squarewave (alternating on and off). You can assemble individual bits to a serial data stream by a shift register, but an unequivocal frame synchronisation must be added. So the resulting data rate will be somewhat higher than 1 kbps. And you have to consider the requirement of RF modules for balanced serial data. Manchester encoding could be used, but doubles the effective data rate.

In most cases, a microprocessor would be the lowest part count solution, but unfortunately requires programming.

P.S.: Perhaps you can give an example, what kind of information is carried by the "pwm" channels.

Click to expand...

my actual need is to transmitt and recieve 8 analog signals
(dc voltage levels that could be between 0 an 5volt)
to the reciever
the reciever should be able to recieve this data and decode it to give me the same 8 dc voltage lines

please do help
thanks

my actual need is to transmitt and recieve 8 analog signals

Click to expand...

Yes, I expected something like this. So the next question is the intended change rate for each input? If you e.g. intend to transmit analog samples with a rate of 100 Hz for each channel, the overall data rate would go far beyond the said 1 kBaud of RF channel. The best way to get a fast reponse ist to transmit the analog voltages digitally (e.g. 8-Bt encoded), and to transmit large changes first. Ends up in using a microcontroller on each end of the RF channel.

FvM said:

Yes, I expected something like this. So the next question is the intended change rate for each input? If you e.g. intend to transmit analog samples with a rate of 100 Hz for each channel, the overall data rate would go far beyond the said 1 kBaud of RF channel. The best way to get a fast reponse ist to transmit the analog voltages digitally (e.g. 8-Bt encoded), and to transmit large changes first. Ends up in using a microcontroller on each end of the RF channel.

Click to expand...

sir can u please give me a heads up on that topic..i will use 2.4 ghz transciever..but i dont know how to do it..
please can u help.
thanks

---------- Post added at 01:22 ---------- Previous post was at 01:14 ----------

ckshivaram said:

which pdf are you talking ... can you be more clear

Click to expand...

i was talking about k175

https://www.kitsrus.com/pdf/k175.pdf..
how to make such an item
what is the input max data rate or frequency of each 8 inputs

If i understand correctly what you want then you don't have to send pwm signals,
you can have a pwm generator in the receiver side (1 or 2 mcu) and just send the setting for each pwm when you want to set or change it.
So for example you can send 4 bytes , each one will have a value of 1 to 200 (for example),
the mcu connected to the receiver will get this bytes and assign each one to a different pwm output for a target pwm duty of 0.5% to 100% (1 to 200 input).

Alex

---------- Post added at 23:09 ---------- Previous post was at 22:34 ----------

I have read your posts again, you obviously don't want to use an mcu so you mean that the receiver bits would drive a few transistors for direct pwm output
but you still need a lot of transmitting rate to do it.
If for example you have a 1Khz pwm signal with 50% duty you need 2Khz transmitting rate but for the same 1Khz to be able to have a duty of in steps of 10% you have
to be able to have a transmitter rate at least 10 * 1KHz because you will actually "break" the 1Khz signal in 10000 divisions and enable only 1000 of them,
for each period you will have 1/10 on and 9/10 off.
So the question is how big are the duty cycle steps (1%, 5%, 10%, 20%...) you need and what is the pwm frequency you want in the output.

Alex

---------- Post added at 23:19 ---------- Previous post was at 23:09 ----------

For a serial to parallel conversion you could use 74HC595 () but how would you drive it correctly from a receiver,
i don't have a solution.

Alex

I notice, that the design ideas are continously changing, e.g. now it's about a 2.4 GHz transceiver instead of a small bandwidth 434 MHz link. No problem basically, but I guess, you won't have a 1 kbaud limitation then. I also notice, that some 2.4 GHz modules offer a direct mode for digital data, so you could possibly transmit time multiplexed pwm data. You have to check the detail requirements however, e.g. DC balanced data streams. Generally, I would opt against direct mode and suggest coded digital transmission, because the only simple way to guarantee a fails safe operation in presence of interferences.

I once designed a circuit that performed pwm time-multiplex through a wired link (for a stage light control). It worked reliably, but the effort has been considerably higher than a today's digital solution, that involves a single chip microcontroller.

thanks for all your help..
but i still do not get any new method to transmit 8 analog signals simultanously...
i wanted the pwm signals to drive the brushless dc motor...

the main aim of this project is to built a transmitter and reciever for a quad copter that has 4 brushless motor drivers ..

that is ..if duty cycle if pwm is less then speed of motor will be less...if duty cycle is more then speed will be more..
if 100 % dutu cycle the brushless motor will run at full speed..

this is why i need the analog signals to control the duty cycle of pwm...but how to recieve this analog signals at the reciever stage,to make pwm needed for brush less esc..

thanks please help.

As FvM said i think you will have a problem if you use a pwm output that is essentially a (live) replay of the live input signal,
if you have any kind of interference or if the link is disconnected your output pwm will be out of control or can get random values.
I'm afraid you have to use an mcu to check the input data, maintain the data and even land safely the quad copter when the
transimer signal is lost (ow when the battery gets low).
Also i think that pwm is not enough , you will also need some kind of rpm feedback to increase or desrease the pwm
to maintain the same rotation speed with different weather conditions (wind)

Maybe something like this will help **broken link removed**

Alex

I think, many retail RC systems will provide simultaneous speed control of 4 DC motors. Today's RCs are digital systems, similar to the suggested solution. Designing your own RC transmitter and receiver based on traditional analog and discrete digital circuits would be basically possible, it's a bit like a DIY tube radio in my opinion. I don't know about the exact properties of your available RF modules nor about your circuit design capabilities.