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Author Topic: RF Transmitter and Receiver WRL-10535 and WRL-10533  (Read 7570 times)
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Yes, 9V battery not the greatest for Arduino. 1/2 the capacity wasted as heat just going thru the regulator.
Using a switching regulator such as this to make 5V and then powering the 5V at the header pin is better.

* R-78Exx-0.5 DC-DC.pdf (70.33 KB - downloaded 9 times.)
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I made a remote control, uses 8 MHz Promini running direct from 3.7V LiPo connected to Vcc line (bypasses regulator).
Keypress creates interrupt, wakes up uC from power down sleep mode, it reads the keypress using the Keypad.h library, sends it out via virtualwire, goes back into powerdown sleep mode.
Uses MAX1811 to charge the battery from a 5V source, like a USB port, but I have a 5V wallwart that powers the receiver, I just move the cord over when I want to charge it. Both have panelmount 5.5/2.1 barrel jacks.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=090-479

or PCB mount if that's your design
http://www.dipmicro.com/store/KLDX-0202-A

wallwarts
http://www.dipmicro.com/store/DCA-0510
http://www.dipmicro.com/store/DCA-0520
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Alrighty then... that is odd.

Trying to figure out why I can't get any range out of it, I removed the transmitter from the 2560 board while it's running, the uno continue to receive the hello message.....  Unplug the 2560 the messages stop, plug it back in they start again.  So apparently even without the transmitter plugged in, the 2560 is putting out enough signal for the receiver to pick it up at close range with no transmitter at all???
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Yep, I'm dumbfounded.  This has got to be one of the most annoying pieces of electronics I have worked with yet.

I can not get more than a 2 inch range out of these things with a 13 cm antenna.  Removing the antenna has a very small impact on performance.  It doesn't increase the range, just helps more of the signals get through at the max range of 2 inches!

At this 2 inches, the receiver will pick up the message from the other arduino board somehow with no transmitter plugged in.  Although with the transmitter plugged in, it picks up the message a lot more consistently.

I'm almost ready to throw these things in the trash  smiley-mad


EDIT:

Ok scratch that.  Looks like I've got at least one bad receiver.  Swapped out the receiver with my 2nd receiver and now I'm receiving messages from one end of the house to the other (about 20 meters).  It was missing some signals at that range but it was picking up at least 3 in 5.
« Last Edit: July 10, 2012, 08:22:32 pm by steven6282 » Logged

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Ok scratch that.  Looks like I've got at least one bad receiver.  Swapped out the receiver with my 2nd receiver and now I'm receiving messages from one end of the house to the other (about 20 meters).  It was missing some signals at that range but it was picking up at least 3 in 5.

That's more like it but you shouldn't stick to that 13 cm antenna. 13 cm is for 434MHz.
The wavelength at 315 MHz is 95.2 cm so a 1/4 wavelength antenna would have to be around 24 cm.

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Ok scratch that.  Looks like I've got at least one bad receiver.  Swapped out the receiver with my 2nd receiver and now I'm receiving messages from one end of the house to the other (about 20 meters).  It was missing some signals at that range but it was picking up at least 3 in 5.

That's more like it but you shouldn't stick to that 13 cm antenna. 13 cm is for 434MHz.
The wavelength at 315 MHz is 95.2 cm so a 1/4 wavelength antenna would have to be around 24 cm.



I never new antenna lengths had anything to do with it.  I only used 13cm because I read that somewhere, don't remember where.  Probably the sparkfun comments on the 434mhz version of the transmitter or something.

13cm is really to long for what I'm doing, 24 cm would be bordering on ludicrous lol smiley  Not unless I can coil it inside a project box and only have a small part sticking out, but that seems like it would defeat the purpose of an antenna.

People say this is a commonly used frequency in alarm systems and such but I don't recall ever seeing anything with a 24 cm antenna sticking out of it, so how do they achieve it?  Like I said if I can coil it around inside the project box I can probably get by, even with 24cm.  The question then is should it be a bare piece of wire, a rubber insulated piece of wire, or something else entirely?  Is one type of wire / gauge of wire better than others if wire is ok to use?  For the project I'm using this in, getting a message through to the receiver is important, but my overall project size needs to remain somewhat small and inconspicuous.
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17cm is for 434 MHz.

315 MHz ~1.5ft,
1/4 of that, ~11cm, should work well
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17cm is for 434 MHz.

Right, it should be 17. My bad.
I've also read 13 in some guides but it should be 17 for 434MHz and that's what I'm using.

Quote
315 MHz ~1.5ft,
1/4 of that, ~11cm, should work well

What is 11cm? 1/8 wavelength?
Guess it should work too.

Experiment a bit. Try 11-12 cm and route it around inside your enclosure and try 24 cm and make more loops. It doesn't necessarily have to stick out.
Maybe it has to if you use a metal enclosure.

Any piece of wire should do. I've used thick single core copper without plastic insulation, thin single core jumper wire with insulation, a multi core wire with insulation from an ethernet cable (there are eight of these in each cable) and that worked fine too. I don't know what's best in theory.

The alarm devices you're mentioning are probably using coil antennas or pcb loop antennas which are a bit harder to get right.
Maybe someone here can tell what dimensions you would need for that.

What kind of range are you aiming for?
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I just have 30 guage wirewrap wire, sits loose on my enclosure.
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17cm is for 434 MHz.

Right, it should be 17. My bad.
I've also read 13 in some guides but it should be 17 for 434MHz and that's what I'm using.

Quote
315 MHz ~1.5ft,
1/4 of that, ~11cm, should work well

What is 11cm? 1/8 wavelength?
Guess it should work too.

Experiment a bit. Try 11-12 cm and route it around inside your enclosure and try 24 cm and make more loops. It doesn't necessarily have to stick out.
Maybe it has to if you use a metal enclosure.

Any piece of wire should do. I've used thick single core copper without plastic insulation, thin single core jumper wire with insulation, a multi core wire with insulation from an ethernet cable (there are eight of these in each cable) and that worked fine too. I don't know what's best in theory.

The alarm devices you're mentioning are probably using coil antennas or pcb loop antennas which are a bit harder to get right.
Maybe someone here can tell what dimensions you would need for that.

What kind of range are you aiming for?

Worse case scenario about 15 meters, but mostly within 10 meters.

I'm still playing with stuff just testing and prototyping right now.  Got some transceivers to try out next if I can figure out how to wire them.  They just use a bit more power which I'm not crazy about since I'm trying to keep these things low enough to run off batteries for a good amount of time.
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Worse case scenario about 15 meters, but mostly within 10 meters.

I'd say you should reach 15 meters no matter what kind of wire and which of the antenna lengths you select as long as it's a length that matches the frequency.
Selecting any other length might not help.

Quote
I'm still playing with stuff just testing and prototyping right now.  Got some transceivers to try out next if I can figure out how to wire them.  They just use a bit more power which I'm not crazy about since I'm trying to keep these things low enough to run off batteries for a good amount of time.

What's the application if i may ask?
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What's the application if i may ask?

Wireless sensors for an alarm system.
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I just found these on sparkfun:

http://www.sparkfun.com/products/690

How the heck do you solder something like that?  It's really cheap and a 2.4ghz transceiver should have a lot less interference problems, and the power usage is between the rf transmitters and the transceivers I  currently have (http://www.sparkfun.com/products/9582)

Does it require anything else to work?  The description mentions something about works great with a 16mhz crystal, does it require that though?
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Do you know for sure that the device is getting 5V? Those little devices usually just work. They worked well for me when I actually made the things before I retired. Clean 5V and Ground, the antenna wires should be about 7" or about 18CM and either vertical or horizontal doesn't matter as long as both are the same way. You might get lucky there as it is possible to decrease the interfering signal by changing antenna polarization, theoretically by a factor of 10, Practically about 1/3.

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You buy it on a board instead:

http://www.sparkfun.com/products/691

http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=53
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