[SOLVED] Remote Controller with ASK transmitter and receiver Problem

[dejavu51]

Hey there ;-) I'm testing a remote controller with pt2262 ic as encoder and pt2272 - m4 as decoder with an ASK transmitter and receiver on a breadboard. when i connect the data out pin of pt2262 to the data in pin of pt2272 with a wire the circuit functions correctly but when i use the ASK transmitter and receiver the circuit won't work. any suggestion would be really appreciated :grin:

here are the ASK modules that I've Used :
**broken link removed**
**broken link removed**

And here is the schematic for my circuit:
**broken link removed**
I used One Voltage Regulator on the Bread board for the Both circuits and I didn't put any switches on the pin 10 till 14, instead I directly wired pin 10 to 5 volt and pin 11 till 13 to ground.

 

[KerimF]

Sorry, I couldn't open any of the 3 attachments

 

[dejavu51]

Sorry, I couldn't open any of the 3 attachments

tnx. the links should be fixed now.

 

[KerimF]

I used a lot these ASK modules in my produced products but to transmit raw data (1's and 0's) instead. The raw bits follow a protocol I wrote for the MCUs in the transmiting and receiving sides.

First of all, you may need to check the polarity of the received signal at the input of the decoder if it is the same of the signal at the ouput of the encoder.

 

[dejavu51]

I'm not sure how should i check that out.Do i Need an osiloscope to check the polarity of the signal? thanks for the reply

 

[KerimF]

Of course with an oscilloscope, it can be done very easily.

In case you don't have one, you may like replace the encoder with a simple 555 oscillator.

By using a 555 timer IC, could you generate 1KHz for example with a duty cycle of about 75%? (high 75%, low 25%).
The measured DC voltage at the input of the transmitter will be about 0.75 * Vcc.

At the receiving side, replace the decoder with a pull-up resistor of 4K7 (between the receiver output and Vcc).
During the continous transmission, measure the DC voltage at the receiver output. If it is also higher than Vcc/2 than the polarities are the same.

 

[dejavu51]

It should take me a day or two to either go to the university lab and test this out with an oscilloscope or buy a 555 timer IC. I will post here the results. by the way if the polarities aren't the same what's the next step? (or are the same )

 

[KerimF]

About the polarity, I think I complicated its test
I mean we can send manually 1 or 0 at the transmitter input, by replacing the encoder with a pull-up resistor (say 10K) and a switch between the data pin and ground.
And check what you get at the receiver output by toggling the switch; 0 (GND) and 1 (high).

The next step is to find out a way to check the frequencies of the data carrier set by R1 (of the encoder) and R2 (of the decoder).
In a way, we can vary to some extent the value of R1 or R2 to check if this is the problem.

Of course with an oscilloscope, the check and adjustment could be made rather quickly.

 

[dejavu51]

:-o you made it real simple for me this time . so I Connected vcc and gnd by a 10 K pull up resister with a switch to the data in of transmitter as you said, and checked data out of receiver with volt meter . here is how I connected them exactly just to be sure it's correct.
**broken link removed**
so when i turn transmitter and receiver on, data out voltage goes from zero to 3 then backward to zero again and after that it settles on 1.5 and jumps a little up and down around that ( data in is connected to vcc at this mode ). when I press the switch ( connecting data in to the ground ) the same process happens all over again and when I let the switch go, It all Repeats Again.
And about R1 and R2 Values . If they weren't correct the circuit shouldn't have worked when i connected the data in and out of the two IC with a wire in the first place. should it? tnx again

 

[KerimF]

First, your last remark about R1 and R2 is good.

I supposed that you connected first each side to its Vcc (likely both have the same Vcc in your experiment now).

But I am sorry, I didn't get well what happened exactly after you pressed the push-button (for a realtively long time as if it is a switch).
Also I also couldn't get what happened after you release the button (switch is off).

Do I hear you say that the steady state voltage, in all cases (switch is 0 or 1), is about 1.5V at the receiver data output (it is better to remove now the decoder and replace it with a pull-up resistor, say 4K7).
For instance, try replacing the previous 10K with 4K7 too.

Just to be sure, is Vcc=5V for both sides?

 

[dejavu51]

The Vcc Is 5 volts . I used a 7805 voltage regulator. and as you said they have the same vcc. you got it right , in all cases steady state voltage is about 1.5 volts at receiver data output. I changed the resistor to 4K7 and put a another pull up resistor at data output. the results are the same except now the steady voltage is 1.2 volt.

I did another test after a few minute I wrote the above paragraph . I tried to use two voltage regulator and seperate the vcc of both sides. this time i didn't get any output at all. So I again used only one Vcc for both sides. On the breadboard there are some wires connected to the ground and some led too. So I did another test and get these wires and led off the breadboard. and now it's working. when i push the switch I get a 1 volt output. and when i release the switch I get a zero volt output on data out of the receiver. So can i Assume this will work if I put it on a pcb instead of breadboard?

 

[KerimF]

About Vcc, I think you agree with me that in the real project there will be two supplies; one for the transmitter and one for the receiver.
I am afraid that you have to try again and get the same result also with two separate supplies or, in the least, separate Vcc with a common ground.

As far as I know, for an ASK transmitter, when a low voltage is at its data input (as 0V when the switch is pushed), no RF signal is transmitted.
By applying a high input voltage (the switch is released), a continuous RF signal is transmitted.

So you found out that 0V at the transmitter becomes 1 at the receiver and vice versa. In other words, the data should be inverted at one of the two sides.

 

[dejavu51]

you are completely right about vcc I'll test that again. and as you said the data is getting inverted but i have no Idea Why. So how can I invert the data at the data out of the receiver? or any other suggestion. thanks for helping me out here

 

[KerimF]

I found this basic circuit on the pdf file of PT2272.
The NPN transistor could be any general purpose one.

Notes:
(1) Please ignore it is for an IR receiver and forget about the LEDs. On the circuit, we are interested only in its small part related to the IC data input.
(2) Here, there is no difference if the data comes from an IR or RF receiving module.
(3) Perhaps you also need the pull-up resistor at the receiver data output (say 10K, not shown on the circuit).

 

[dejavu51]

I separated the vcc for both side and now it works fine when I connect the data pin of pt2262 to data pin of pt2272 by a WIRE . it still won't work with transmitter and receiver . When I tested the transmitter and receiver with separated vcc and pull up resistor , the data out of receiver gives random data between 1 and 2 ( it doesn't change when the switch is pushed or released ). I'm gonna test out the circuit you posted tomorrow and some other tests too . It's 2 am here and I'm feeling Sleepy tnx again

 

[KerimF]

I wonder if you forgot adding a small piece of wire as antenna to each side (at the transmitter and receiver module)

 

[dejavu51]

No i didn't forget Antenna. The receiver had a piece of soft wire as antenna and I added another one ( 24 cm soft wire wrapped around a pen to make it like a self ) for transmitter myself. So I Tested the transmitter and receiver with a pullup resistor and separated Vcc . I get random data output from receiver from 1 volts to 2 volts and even zero sometimes. when i push the switch it look likes it effects the output for a moment and the output goes around zero volts then it goes back to it's random up and down between 1 volts and 2 volts. So I guess I'm Back At square one. could it be that the transmitter and receiver are broken? and If I get a new one it may work?

 

[KerimF]

For instance about the antenna length, as you know it is here about λ/4 hence it is 75/F (in meter if F is in MHz).

When I worked with TX and RX modules, I bought pairs for two bands; 433 MHz and 315 MHZ.
Is it possible that your TX and RX modules are not for the same UHF band?

 

[dejavu51]

on my transmitter there is a BX R315A so I'm gonna assume it's a 315 MHz . so my wire length for the antenna is 24 cm. But I can't find anything to say my receiver is 315 MHz too . of course except that where I buy these they gave them to me in pair so I guess they are both 315 MHz maybe. and the receiver had it's antenna connected when I bought it and from what i see it's around 23 cm ( I didn't straighten the wire and instead counted the circles ).

 

[KerimF]

Mistakes may happen anytime.
But if we assume that the receiver is also for 315 MHz, perhaps it is not tuned well and this decreases its reception sensivity.
Sometimes this happened to me (since I bought the modules by 100's). To verify this, you can let the TX and RX modules be very close to each other and check if the link works as expected. On my side, even a signal from a 315M TX can be detetected properly by a 433M RX, if they are very close.