Transmitting and Receiving State Information

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homeproject
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Transmitting and Receiving State Information

Post by homeproject » Thu Jul 06, 2006 12:27 pm

I am currently building a device that transmittes one of eight different states to a receiver over RF. I currently have the device able to light up an appropriate LED when it is in each of the states - but I am wanting to get it to be able to send simple data (maybe the number 1 through 8 depending on which state the device is in).

Can you please give me some information as to the best solution to get this device to send this data??

The range does not have to be very far - ideally, I would like the data to go to a transmitter that is attached to a PC.

I am hoping to find some sort of solution or kit that can give me the components that I can add to my device.

I look forward to your response!!!

JPKNHTP
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Post by JPKNHTP » Thu Jul 06, 2006 12:49 pm

-JPKNHTP
-God Bless

homeproject
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Re: Transmitting and Receiving State Information

Post by homeproject » Thu Jul 06, 2006 12:55 pm

Thank you for the quick reply. I am not currently transmitting the state, but want to be able to.

At the present time, I have mercury switches which complete the circuit and turn on the appropriate LED.

I would like the device to be able to transmit data saying which of the 8 LEDs is currently lit up (only one lights up at a time). Each mercury switch and LED has its own power source (2 AAA Batteries).

JPKNHTP
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Post by JPKNHTP » Thu Jul 06, 2006 1:02 pm

-JPKNHTP
-God Bless

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philba
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Post by philba » Thu Jul 06, 2006 1:12 pm

Check this site out. lots of possibilities. http://www.rentron.com/PicBasic/RemoteControl.htm

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jollyrgr
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Post by jollyrgr » Thu Jul 06, 2006 7:56 pm

There are many possible solutions, the cheap RC cars being the most economic and straight forward as suggested by JPKNHTP.

Another is DTMF tones, as many hams and other systems use. You could use a simple baby monitor pair on 49MHz and a computer sound card with free software, such as this:

http://www.qsl.net/kb5ryo/dtmf.htm

A DTMF encoder could be electrically or even accustically coupled to the BABY side of the baby monitor. Audio at the receiver end could go to the LINE IN of the computer.

A cheap phone can be used to generate the tones. In fact you could possibly buy all the stuff at a Salvation Army or Thrift shop for under five dollars. Cheaper of course if you have these lying around gathering dust.

Even better, get a cordless phone and interface the inputs 1 to 8 to the keypad. Power the base end of the setup with the included power supply. Power the handset with a spare 3 or 5 volt wall wart. With a SLIGHT bit of modification, namely a DC supply and a resistor, you can get the audio out of the "PHONE LINE" connection of the base. Since the phone base has a DC supply, you are one resistor away from being able to do this. If you are willing to experiment, you could take the audio signal from where the base demodulates the RF signal. A word of warning: Disconnect the mic on the phone handset. Otherwise someone with a simple radio scanner can hear every word said around this setup. Same holds true for the baby monitor.

If you want to decode the tones from the audio signal, you can also use hardware. A chip like the 8870 should work nicely. They should still be around. Here is a web site that has a project pair of both encoder and decoder:
http://www.boondog.com/tutorials/dtmf/dtmf.htm

There are also kits available with all the parts needed.

You can also use a tone reader/decoder and skip the computer altogether. These are used to dislay the DTMF codes as they are sent and are displayed on an LED or LCD screen. In your case you would encode the signal, send it over the RF link of your choice, feed the audio at the receiver end to the decoder. Some are in kit form, others fully assembled. One nice kit is under $25 and will even send serial signals to an attached computer, if desired. See this http://www.electrokits.com/electronics/ ... ts/128.htm
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