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Topic: tx rx raw voltage output (Read 113 times) previous topic - next topic

Donsa

Hi guys, I have a simple question regarding a cheap tx rx for arduino.

So Im building a heating glove that heats up at certain intervals (ex. 1 sec ON, 5 sec OFF). Since the circuit will sit on my wrist, dimensions are very important.

I want to use 2 gloves, but I also want one to be the "master" (this will be the one I use to change the heating intervals, with OLED+buttons) and a "slave" (only for receiving the intervals and executing them on the second glove).

Also, I noticed that cheap tx and rx only have 3 pins, Vcc, Gnd and Data. I would assume that the Data pin works by outputting high and low voltages to communicate with the arduino.

Based on this assumption, my question is, can I use a rx on the slave glove WITHOUT a 2nd arduino? (to do this I would connect the data pin to the Gate of the N Mosfet, and make it go HIGH for how long the interval is).
Is my reasoning wrong?

Thanks for taking the time to read through all this ;)

DrAzzy

#1
May 16, 2018, 10:13 pm Last Edit: May 16, 2018, 10:16 pm by DrAzzy
Do you mean those cheap 433mhz / 315mhz OOK RF transmitter/receivers?

Those use automatic gain control, and adjust their sensitivity to give ~50% duty cycle output, allowing them to work under a wide variety of ranges and conditions without adjustment. As a consequence of this, you get random gibberish out when there's no signal, as it amplifies noise until it gives 50% duty cycle output. You also get random gibberish if you leave the transmitter on, as it cranks the sensitivity down until it gives 50% duty cycle output. The only way to transmit data is to send a pattern with ~50% duty cycle, and send it several times to ensure receipt (often you may also see a "training burst" with 50% duty cycle at the start of a set of data So you need something with some smarts on the receiving end.

You can get something like this, though, and "push" the buttons on the transmitter with the arduino (IIRC the buttons ground a pin of the IC when pushed) - these have an encoder and decoder chip on them. (no specific endorsement of this vendor; they also make ones with relays built in and stuff - search 433mhz remote control 4 channel ) https://www.ebay.com/itm/IC2262-2272-4-channel-wireless-remote-control-kits-4-key-wireless-remote-433MHZ/201497893369
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

DVDdoug

Quote
Also, I noticed that cheap tx and rx only have 3 pins, Vcc, Gnd and Data. I would assume that the Data pin works by outputting high and low voltages to communicate with the arduino.

Based on this assumption, my question is, can I use a rx on the slave glove WITHOUT a 2nd arduino? (to do this I would connect the data pin to the Gate of the N Mosfet, and make it go HIGH for how long the interval is).
Is my reasoning wrong?
TX & RX implies some kind of serial communication (RS-232?).   Bytes are converted to bits and one bit at a time is transmitted, and of course the receiver has to re-construct the bytes.   There are various protocols and the transmitter (TX) and receiver (RX) have be using the same protocol and the same data-rate etc.   Both the transmitter and receiver need a microcontroller, or some kind of clock and logic.

(The Internet uses serial communication... One bit at a time...)

If you just want to read the state of one or more switches you can use a single binary (high/low... on/off) digital input so you don't need "TX" and "RX".


Donsa

ok thank you guys, very helpful. I will add the extra arduino so i can measure temperature and battery life too with simple circuits and program.

Thanks again.

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