SparkFun Forums

[viswanathan.krishnan]

Hi

I am new to this forum. I am doing a project which requires me to establish wireless communication. I am planning to use RF-KLP module for that. Can anyone tell me how much range can be obtained using it when communication is not line of sight. Also what antenna should be used for increasing the range of the module.

Thanking you

[snappy]

Here's a link to Laipac website that tested the TLP / RLP modules.
http://www.laipac.com/Downloads/Easy/TL ... _range.pdf

[viswanathan.krishnan]

Thanks for the reply. Can anyone please help me with antenna design for these modules. I would like to know if a copper wire would be enough as an antenna.

[riden]

You asked about the range, but didn't indicate your requirements or the environment where these units have to work. The use of the term "not line of sight" was a red flag for me, and images of having to communicate over a range of several miles pop into my mind. These units won't do it. They are low power units designed for distances of a few hundred feet maximum.

If you are talking about having to communicate through obstructions, the range depends upon the type of obstruction. Having the receiver or transmitter inside a metal building will present challenges. These units operate in the low UHF frequency range so they are impacted by obstructions more than lower frequency units (e.g., 27MHz or 49MHz units), but less than higher frequency units (e.g., 2.4GHz). I have a reliable link of around 100 feet using 6.5" antennas (going through three wooden walls, a single layer of brick, and about 80 feet of open air). Your results could vary.

The simplest antenna would be an omni-directional 1/4 wavelength vertical (about 6.5" for 432Mhz, 9" for 310Mhz), which could be a piece of wire. However, you can employ more directional antennas such as a yagi to increase your range by directing the energy in the direction of the tx/rx instead of omni-directionally. Yagi's can be home brewed or purchased ready made.

[viswanathan.krishnan]

Thanks for your reply. Actuall i would be using it inside a building. So i wish to communicate between the third floor and ground floor in a normal office.

I connected the circuit as per the diagram given in walk through however I am not able to glow an LED in the data pin of receiver. Is there any error in my circuit or do any of u know any other reason. I have kept them in the same bread board. So range is not the reason.

Please guide me regarding this

[viswanathan.krishnan]

Also I would like to know how I can test the module. Can I just give transmitter data as 5v and then connect a LED in receiver data pin and check. Please help me regarding.

[riden]

You can key the transmitter on and off, and the receiver's output will respond. I'm not sure that the output of the receiver can directly drive an LED, at least I've never used them in that way. Be sure that you have included a fairly large (4.7k - 10k or so) current limiting resistor in series with the LED if you go that route, or use a multimeter to observe the receiver's output.

If your application is such that you press a button and something happens on the other end (LED lights, relay closes, etc.), you will want to use an encoder/decoder chip pair like those available from Holtek or Rentron, or microcontrollers on each end. You need something more than just keying the transmitter on and off with a switch.

[viswanathan.krishnan]

Thanks for your reply. I tried using a simple on/off switch. But its still not working. My antenna in transmitter side shows greater than 5v but the antenna in the receiver shows in millivolts range always and my output in receiver data pin remains in millivolts. What could be the problem for this.

[Philba]

lots of issues here. first, how are measuring the output of the receiver?

To answer your last question, no, you won't get the effect you wanted from an LED. Most likely it will just flicker if it lights at all. If you want to do simple testing, use some sort of decoder and decoder chips. I don't think SFE carries that stuff but there are some here along with schematics - http://www.rentron.com/PicBasic/RemoteControl.htm

[saipan59]

Can I just give transmitter data as 5v and then connect a LED in receiver data pin and check.

No, that generally won't work.
When the xmtr is off, the rcvr will be outputting 'random' data all the time.
And as Ralph hinted, it is likely that the rcvr cannot drive an LED directly anyway.
The "KLP Walkthrough" on the SFE site is really not adequate to get started with (I wish they would fill in all the missing details!).
Realistically, you need either a microcontroller, or a dedicated encoder/decoder chip at each end of your RF link.

There are several topics in this forum where folks (Ralph, myself and others) have described the details of actually making an RF link work with these very simple (low cost) modules. Some of us have posted schematics and source code. It's much more complex than just the KLP modules.

Pete

[saipan59]

Here's one of the threads that discusses the details:

viewtopic.php?t=6017&start=0

Pete

[norlin]

Just remember when testing to have the receiver and transmitter at least 6ft apart. I had a lot of trouble receiving garbage until I seperated them by at least 6ft. See:
viewtopic.php?t=9883

[viswanathan.krishnan]

Thanks for your reply. I would like to know if anyone has worked on 8051 microcontroller and used it to interface it with the KLP modules. If yes can anyone send the schematics or diagram to viswanathan.krishnan@honeywell.com

I have code for serial communication so that must not be a problem However I would like to see a snapshot of the connection. I have been trying for past one week for its working however I have not been successfull as of now. Please help me regarding this. I use the 8051 development board to send the serial data from microcontroller to the RF transmitter and from data pin of the receiver I am feeding it to the RX pin in the RS232 which is present in the development board itself. However I am not able to get any output.

[riden]

Interestingly enough, when I did a search for 8051 and RLP on the forum, this thread came up: viewtopic.php?t=9052&highlight=8051.

Is this what you're looking for?