Testing RF Module (315MHz)

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Testing RF Module (315MHz)

Postby PIGBAOBAO » Thu Dec 09, 2010 7:05 pm

Hi,

Is anyone can guide me and tell me the method to check the function of a RF module (315MHz) is work or not?

Now i am going to check the RF module by using a click button that connected with data pin at transmitter side and a led at receiver side. (Without any PIC or device and Both RF module are install a wire as antenna). Both are connected with difference power supply. So what i want to check is when i am click the button and the led will be light up.

Is my method to check the RF module is fine to perform is correct? Or any other method can teach me to check the function of RF module?

And could the transmitter 315MHz can receive analog input such as click button and the signal will be received by receiver 315MHz?

Please help me...Thank!
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Re: Testing RF Module (315MHz)

Postby yonghui » Thu Dec 09, 2010 8:33 pm

hi,

u can refer cytron DIY project for the testing. there is a set of DIY projects related to the low cost RF.

button click is analog? i thought is digital.
analog value shud be converted to digital through ADC before transmitting it.


regards,
yh
thanks&regards,
yh
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Re: Testing RF Module (315MHz)

Postby ABSF » Thu Dec 09, 2010 9:42 pm

Now i am going to check the RF module by using a click button that connected with data pin at transmitter side and a led at receiver side. (Without any PIC or device and Both RF module are install a wire as antenna). Both are connected with difference power supply. So what i want to check is when i am click the button and the led will be light up.

Is my method to check the RF module is fine to perform is correct? Or any other method can teach me to check the function of RF module?


Are you saying that if you send 0V on the data of Tx Module, you're expecting a 0V at the data of the Rx Module? And if you're sending +5V, you'll get +5V on the Rx side?

I tried to examine the Tx and Rx module with a magnifying glass and found that the Tx Module is made up of 3 transistors and the data pin goes through a 20K resistor before entering the first transistor. The Rx module has an op-amp LM358 on it. The op-amp is either used as an amplifier to amplify the received signal or as a comparator. The input can be either AC coupled or DC coupled.

You may test by applying a low voltage say 2V on the Tx's Data pin and put a voltmeter on the Rx's Data pin. If there is nothing on the Rx then increase the voltage to 3V and watch the voltmeter again. If the module is DC coupled, you should get something on the voltmeter.

See the discussion here:

http://www.electro-tech-online.com/gene ... e-ask.html

Putting a LED on the data pin to test is not a good idea. If the output is not able to drive 20mA, you might spoil the Rx module (LM358).

Allen
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Re: Testing RF Module (315MHz)

Postby PIGBAOBAO » Thu Dec 09, 2010 11:57 pm

Hi thank for reply,

Hi yong hui,
Sorry about my mistake, the button is digital input, so if i am using potential meter as input then izit the RF transmitter module is not work? (without any external device such as PIC so signal does not go through ADC).

I have revised the Cytron DIY project but it testing by using PIC an show at 7-segment, but now I just want to test that 2 RF module is work or not by connected to power supply only.


Hi ABSF,

[Are you saying that if you send 0V on the data of Tx Module, you're expecting a 0V at the data of the Rx Module? And if you're sending +5V, you'll get +5V on the Rx side?]

yup almost like that, so if i have apply 5V on the data of Tx Module, and i get 0V at the data of the Rx Module, so can i say it does not work?

This is my another method, i try to connect a pushbutton between the power supply(operating Voltage = 5V) and the data pin of Tx Module, and a oscilloscpoe probe click on the data pin of the Rx Module to check the waveform. So when i pressed the pushbutton on the transmitter side and a random waveform will be given in the oscilloscope screen and consider the wireless transmission is successful. So it is work with my idea?

Sorry for my ignorance, i am new in this. can u tell me what is the difference between AC coupled and DC coupled? And what is the effect if either is?

Thanks in advance!
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Re: Testing RF Module (315MHz)

Postby ABSF » Fri Dec 10, 2010 7:26 am

[Are you saying that if you send 0V on the data of Tx Module, you're expecting a 0V at the data of the Rx Module? And if you're sending +5V, you'll get +5V on the Rx side?]

yup almost like that, so if i have apply 5V on the data of Tx Module, and i get 0V at the data of the Rx Module, so can i say it does not work?


From the discusion link that I have attached, the guys there said if you send 5V you will get about 3V only. By right it should work if it is DC coupled. DC coupled means that there is no capacitor blocking the DC before enter Data pin and exiting output data pin at Rx module. Or else it is AC coupled.

A better RF module set is here :
http://www.winpicprog.co.uk/pic_tutoria ... _board.htm

and the datasheet is here:
http://www.winpicprog.co.uk/download/wireless.pdf

This is my another method, i try to connect a pushbutton between the power supply(operating Voltage = 5V) and the data pin of Tx Module, and a oscilloscpoe probe click on the data pin of the Rx Module to check the waveform. So when i pressed the pushbutton on the transmitter side and a random waveform will be given in the oscilloscope screen and consider the wireless transmission is successful. So it is work with my idea?


If the module is DC coupled, you should get a straight line (DC) on your scope + a lot of noise.

Allen
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Re: Testing RF Module (315MHz)

Postby PIGBAOBAO » Fri Dec 10, 2010 4:03 pm

Hi ABSF,

Thank for your sharing. I have a question.
I check the datasheet of cytron product wireless 315MHz receiver and i found that some note has been given :

"If the module is used with microcontroller, the clock frequency should be under
4MHz. Please try to keep a distance between oscillator and the RF Receiver module
to avoid the disturbance from oscillator."

I will try to combine and work with PIC16F877A in advance, but i was realized that PIC16F877A has a 20MHz operating frequency. So, when i am getting to start writing the coding in MikroC and will set a 20MHz of operating frequency for PIC16F877A. Since the NOTE has mentioned about 4MHz for receiver, so should i changed the operating frequency of PIC16F877A to less than or equal to 4MHz?

Or i have misunderstanding about operating frequency NOT equal to clock frequency?
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Re: Testing RF Module (315MHz)

Postby ABSF » Fri Dec 10, 2010 9:42 pm

"If the module is used with microcontroller, the clock frequency should be under
4MHz. Please try to keep a distance between oscillator and the RF Receiver module
to avoid the disturbance from oscillator."

I will try to combine and work with PIC16F877A in advance, but i was realized that PIC16F877A has a 20MHz operating frequency. So, when i am getting to start writing the coding in MikroC and will set a 20MHz of operating frequency for PIC16F877A. Since the NOTE has mentioned about 4MHz for receiver, so should i changed the operating frequency of PIC16F877A to less than or equal to 4MHz?

Or i have misunderstanding about operating frequency NOT equal to clock frequency?


I know what you mean...But take a look at the P9 & P10 of the PR16 description here:

http://www.cytron.com.my/usr_attachment/PR16_DD.pdf

You'll see that the crystal used is 20MHz, but the boards still work. So I think it doesn't mean that you cannot use 20MHz crystal frequency. But the crystal osc should be kept a distant from the Tx or Rx modules. Or you should screen the modules well to prevent disturbances.

Read all the past posts on "RF transmitters and Receivers", and I came across one post from Shahrul who mentioned that the baud rate should not be too high or else it wouldn't work.

Allen
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Re: Testing RF Module (315MHz)

Postby joy19861111 » Mon Jan 03, 2011 1:30 pm

i jz wan to comfrim that the receiver or the tramsitter is work fine. i hv the RF module wif 315Mhz, when the TX data is high, 5V the rx data is in 1.90 - 2.20V when the tx data is low 0V the rx data is in 1.90 - 2.20v. What is the problem?? is that the rf odule is defected???
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Re: Testing RF Module (315MHz)

Postby shiyan » Tue Jan 04, 2011 10:06 pm

I don think the low cost RF module can be checked the functionality in such a way. Try giving pulse to transmitter, and check the receiver, you should get similar pulses. But the frequency of pulses cannot be too fast, 1KHz should be fine.
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