Hi. I am reading that tutorial https://idyl.io/arduino/how-to/syn115-syn480r-rf-wireless-transmitter-receiver/
However i still do not understand why he is using on the transmitter those resistors.
Since he is connecting the 3.3V from the arduino to the breadboard and since that rf transmitter works with 3.3V why does he need the resistors in both data pin 12 and ground?
thanks
He's using it as a voltage divider to prevent the 5v data line from the arduino from damaging the SYN115 which is running at 3.3v. I am 99% sure that I have used those transmitters at 5v without issue.
I have used those things at 5v with no problems, personally shrug At least, I'm pretty sure I did. Using a 3.3v-only transmitter when 5v ones that are comparable or better are readily available is such a poor decision that I generally question his judgement.
In any event, in my testing, I got (slightly) better range using the el-cheapo green transmitters that are usually paired with those worthless green receivers. I use the RXB-12 or RXB-14 receivers (SYN470 and SYN480 respectively - the former is a 16 pin part with a bunch of special function pins that aren;t used in the receivers, while the 480 is the 8-pin version with a all the pins that set the modes hardwired and not as many pins exposed.
That said, the best transmitters I found were the STX882's - the SRX882 receivers they're often paired with are like half the range of the RXB-12, and more expensive too, but those transmitters are about 10-20% better than the cheapo greens, which are about 10-20% better than the SYN115 based ones. But in 315/433mhz RF, the receiver matters FAR more than the transmitter. Difference between best and worst transmitters I tested wasn't even 2:1 on range. Difference between best (RXB-12) and worst (the cheap green) receiver was >20:1.
(the code and wiring for them all is the same)
DrAzzy:
He's using it as a voltage divider to prevent the 5v data line from the arduino from damaging the SYN115 which is running at 3.3v. I am 99% sure that I have used those transmitters at 5v without issue.
The datasheet definitely says input abs-max voltage for Vdd is 5V, and for digital inputs is Vdd+0.3V, so you've been lucky - running at the abs-max limit is risky. You'll probably be generating harmonics at levels significant above the datasheet specificaions too, which are only given for 3.0V.
Did you manage to get range of like 10 meters with walls in between?
if those transmitter modules are connected to a attiny85 which is powered with 3.3V, we do not need those resistors. is that correct???
chris700:
if those transmitter modules are connected to a attiny85 which is powered with 3.3V, we do not need those resistors. is that correct???
Yes.
I got range far better than that with RXB-12 (other SYN-470/SYN-480 receivers are comparable). I was doing 1200 feet line of sight with a cheap green transmitter, IIRC 1400 or so with STX882 transmitting. Those SYN470's are amazing receivers, and cheap as dirt.
chris700:
if those transmitter modules are connected to a attiny85 which is powered with 3.3V, we do not need those resistors. is that correct???
yes that's correct