I am trying to build a basic RC boat with my daughter. Instead of using a premade module, I thought building it ourselves would be more fun but I hit a roadblock almost at the start.
I built a very basic transmitter circuit with PT2262, PT2272-M6 and a cheap RF couple exactly like this: 433Mhz RF Module Kit | ePartners NZ
And it didn't work. I have two problems:
1- When hold the switch on the transmitter side, I can see in the multimeter that, PT2262 stops giving an output after 2-3 seconds.
2- On the receiver side, the data pins of the receiver are about 3.5-4.2V (I don't have an osciloscope so I measured with my multimeter. I am guessing this is noise since it changes when I get my hand close to the antenna). When I press the switch, it drops to 1.8V and when I release the switch, it drops to 0V and quickly gets back to 3.5-4.2V. And PT2272-M6 doesn't do a thing with this signal. I am assuming signal is not what it is expecting.
I tried bypassing the RF modules by connecting the Dout of PT2262 to the Din of PT2272-M6 via a cable and it works. So encoding and decoding does not have a problem. But I cannot find the reasons of these two problems.
Test the RF modules using a couple of Arduinos and one of the simple RadioHead or VirtualWire ASK examples. Countless tutorials covering those approaches are posted on line.
Thank you @kmin for pointing that out. I tried using 2 AA batteries to power the transmitter with 2.9V but the result is the same unfortunately.
The receiver data out is about 4V while nothing is transmitted. I am guessing this is the noise caused by the self adjusted gain of the receiver. When transmission is active, it jumps to a lower and much stable voltage. But PT2272-M6 is still not happy with what it is getting.
Most of the videos on YouTube are using PT2272-M4 instead of -M6. I thought the only difference is 2 extra output pins. I don't have any -M4s so I cannot try with that kind.
@jremington Today I was going to build one of those sound card oscilloscopes. If I can find time after work, I'll also try to diagnose with arduinos. Thanks.
I also tried with PT2272-L4 but the results were same.
What I noticed is, the Dout of PT2262 is about 1.3V when the switch is pressed but the Dout of receiver is about 1.6V when the switch is pressed. So it looks like the signals are different but I'll have a better picture after arduino/sound card diagnosis.
Not really the same, 2.9V doesn't damage the transmitter.
Do what @jremington suggested on post#4, it's easier to work when you know that you have working 433 rx tx setup.
First, as suggested, I tried sending a string using RadioHead. Found a very simple code online, hooked up two Arduinos and it looks like the transmission is successful. Here is the screenshot. Both circuits are extremely simple: Just an Arduino and an RF module connected to a pin.
After this, again as suggested, I built a 2 channel probe to use with my sound card to observe the signal in my PT2262 and PT2272-L4 circuits. And found an interesting possible problem. The signal on the TX side is the output of PT2262 and the Data input of the transmitter. The RX side is the Data output of the receiver. As seen in the image, the start of the signal is a little bit different on both sides. Anyone have a guess why this would happen?
Looking at the signals of PT2262 and Arduino output pin, I realized that PT2262 has a much higher frequency. So, I changed the OSC resistors of PT2262 and PT2272. It worked. The problem was the high frequency of encoing all along.
