problem with sending data using RF module

[mister_e]

OK, i'll start a new thread later about how using the internal comparators.

Do you have any oscilloscope?

In meantime you could do some test with an external comparator... LM339 and.. yeah lm741 or any other op-amp COULD work.

[rano_zen06]

OK, i'll start a new thread later about how using the internal comparators.

Do you have any oscilloscope?

yes, there's a digital oscilloscope at my lab. But at this time, my lab still not open for student. It's just 6.30 in the morning here..so, must wait for 2 hour before I can use it.
I will use the oscilloscope later to check the output of RF module.Then I will attach the picture of TX and Rx signal for your review.

[dhouston]

Almost all (in fact, all of the many that I've used) ASK RF receivers have a dataslicer just before the digital output. The dataslicer uses a comparator (as I explain at http://davehouston.org/RFTipsTricks.htm). Adding another comparator might be useful for educational purposes but is of little practical value (IMO). In this case, the only output from the receiver is digital so the noise pulses will have the same amplitude as the data and the duration of the noise pulses are likely to be nearly the same as the bit period. What kind of comparator circuit are you planning?

It is far simpler to use a relatively wide sync pulse followed by the data. The receiver can look for the sync pulse and only after receiving it, look for the data. The data can use almost any protocol desired, including RS232 with or without manchester coding. The single, wide sync pulse works much better than multiple $55 sync bytes. I also recommend sending 3 or more copies of each packet, including the wide sync pulse.

[rano_zen06]

Almost all (in fact, all of the many that I've used) ASK RF receivers have a dataslicer just before the digital output. The dataslicer uses a comparator (as I explain at http://davehouston.org/RFTipsTricks.htm). Adding another comparator might be useful for educational purposes but is of little practical value (IMO). In this case, the only output from the receiver is digital so the noise pulses will have the same amplitude as the data and the duration of the noise pulses are likely to be nearly the same as the bit period. What kind of comparator circuit are you planning?

It is far simpler to use a relatively wide sync pulse followed by the data. The receiver can look for the sync pulse and only after receiving it, look for the data. The data can use almost any protocol desired, including RS232 with or without manchester coding. The single, wide sync pulse works much better than multiple $55 sync bytes. I also recommend sending 3 or more copies of each packet, including the wide sync pulse.

I use oscilloscope to check the data pin for my Rx and Tx module without comparator and the result is not very good.The signal I got show a lot of noise especially at my receiver. You can see the waveform picture at my attachment. I also add the comparator using LM741 to my Rx but something bad happen.my LCD shows nothing and my voltage drop from 5v to 2.3V. I think there is something wrong with my comparator circuit.So..I attached together the schematic of my comparator.Anyone here..please help me to troubleshoot this problem.

[JD123]

Check your comp drawing. If it's correct, you're sending the comp to rails. I think you ment to take the output of the rec to the inverting input, not ground. The 100uf cap is a bit much. I'd use a 1uf or even a .1uf.

Also, what's the signal look like at 1.8khz (same speed as the tx). Your receiving scope pix says you'r reading at 19.3mhz. If your data is riding on the noise at 1.8khz, you'll need to filter the noise in a LF band pass amp.

[mister_e]

There's a load of noise indeed... with that signal.. i don't feel the comparator will be of any help... need something else indeed...

I have to ask, The RX signal is the one [from the Receiver Without your comparator connected too and a Pull-up on Vcc] or at the output of your LM741.. which will never work as is (forget pin 5 and 1, and connect pin 3 directly to RX pin).

Maybe the following link will help you a little bit
http://www.uoguelph.ca/~antoon/gadgets/741/741.html
http://www.ecircuitcenter.com/Circui...mp/op_comp.htm

[rano_zen06]

There's a load of noise indeed... with that signal.. i don't feel the comparator will be of any help... need something else indeed...

I have to ask, The RX signal is the one [from the Receiver Without your comparator connected too and a Pull-up on Vcc] or at the output of your LM741.. which will never work as is (forget pin 5 and 1, and connect pin 3 directly to RX pin).

Maybe the following link will help you a little bit
http://www.uoguelph.ca/~antoon/gadgets/741/741.html
http://www.ecircuitcenter.com/Circui...mp/op_comp.htm

It' s not the output from my LM741. At the moment my Rx data pin connected directly to port A.0. also not using pull up on vcc at that time. In your opinion., should I use filter??