Conrad_Turbo said:How would it know which transmitter is sending the signal? Or which data pin on that transmitter? That is what stumps me. I have a hard time visualizing how it can decipher which signal is which and how it ouput the difference. That way I can use my microcontroller to read that and then with the coding, control an output based on the all the inputted info.
pc88 said:One more thing about I noticed about the receiver ... I think the address lines are inputs to the chip. That would mean it only responds to data from the configured address. If you were thinking of setting different transmitters to different addresses, then you'll have to tap into the raw data signal and perform packet decoding yourself.
Conrad_Turbo said:Thanks for the links, so with something like that I'd need 1 transmitter per sensor (of course) and need 1 receiver per used transmitter? For example if I have 5 sensors around the yard, I will need to order 5 pairs correct? Then I will have 5 receivers connected to the microcontroller? I would also have to specify that I need 5 different frequency pairs?
I could see a RX/TX setup like that being ideal for wireless programming of the microcontroller, or pulling information off it wirelessly.
pc88 said:With something like the Spark Fun devices you can get away with using only one receiver and N transmitters like this: set each transmitter to a different address; on the receiver, tap into the digital output (pin 2 on the RLP434) and do your own decoding of the signal with a microcontroller:
https://www.electro-tech-online.com/custompdfs/2007/07/TLPRLPA-1.pdf
It's more work, but I'm sure it's been done before, and I'm sure the Holtek encoder protocol is well-known.
Then you can monitor traffic from all the transmitters. They would all be transmitting on the same frequency, but this shouldn't be a problem if the transmissions are short.
I don't think having your sensors send data as a pulse frequency is going to work all that well. A better idea would be to have your 555 increment a counter which is tied to the transmitter data lines. Periodically trigger a transmission and then clear the counter.
Conrad_Turbo said:So in total I'm looking at a total point A-B wireless cost of $19.95. However if I want to buy another transmitter how would that work since Sparkfun sells them as tuned pairs? Then with every additional transmitter I'd have to use the HT12E unit.
Nigel Goodwin said:If you're using a micro-controller why use the Holtek chips?, just use your existing micro-controller to do the same job - the Holtek devices are simply pre-programmed micro-controllers.
Conrad_Turbo said:To be 100% honest I am involved more with mechanical engineering than electronics engineering, and I am not familiar with how to write code to decode the transmission... I'm using a BasicX-24 for this project. If you have any tips or links that may be of help I am all ears! Writing the code would save me $1.50 and a lot of input pins on the microcontroller, however I would still need the HT12E correct?
pc88 said:You'll need some sort of data encoder on the transmit side - either a HT12E or microcontroller will work.
pc88 said:We've discussed a lot of ideas in this thread, and my overall advice would be that you go down a path that you know you can make work. Don't worry about getting it right the first time (that's rarely happened to me!) You'll learn a lot just by getting one prototype working, and it will help you decide what the second iteration of your design should look like.
pc88 said:That said, let me describe how using a micro-controller (in both the receiver and transmitter sides) could help your design:
- most uC's have built-in ADC units and this would eliminate the 555 and associated circuitry needed to digitize your sensor reading
pc88 said:- a uC can encode the data packet into a serial bit stream thus performing the function of the HT12E
pc88 said:- a uC can decode a serial bit stream into data bytes thus performing the function of the HT12D
pc88 said:- a uC can manage the power of your application; it can turn off circuits (even external ones) that are not in use, and itself can go into sleep modes in which it only consumes microamps. This could be very beneficial for battery-powered applications which are only intermittently active.
pc88 said:Again, I would urge you to adopt an approach which you are confident you can succeed at. Often it's more valuable to get something working than to come up with the "best" solution (however that's measured.)
Nigel Goodwin said:My tutorials provide code for both transmitter and receiver, using Manchester coding - but it's in assembler.
Conrad_Turbo said:pc88 you mind answering these questions for me?
However if I do go with say the 4800bps RF link from SFE, can I buy 1 receiver and 10 transmitters? I know they are purchased in "matched pairs", but if I need to add more transmitters what do I do?
That's all I think I need to know.
pc88 said:If you're asking whether or not all of the, say, 433.92 MHz units will interoperate with each other, then I think that's true, although I would confirm that with either SparkFun or the manufacturer.
pc88 said:Let me know if you want to get into PIC or AVR microcontrollers. They would be very well suited for a project like this and only cost $2-$3 a piece. Also, let me know when you want to add more transmitters - I'm pretty sure I can help you out with the decoding process.
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