Best (easiest, cheapest) RF connection method?

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I'm posting this here because I didn't think it fit well into any of the wireless forums.  I need to replace wired buttons with some sort of RF key fob connection.  All it needs to communicate are signals for UP DOWN LEFT RIGHT APPLY.  Range is maybe 3m max.  So, short range, low data rate.  It should be dirt-simple (its OK if every key fob activates every receiver) and as always, cheap.  So what is currently the best approach to do this?  I'm always a decade behind on this kind of stuff!  

Thanks.

 

Mike

 

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Best; Easiest; Cheapest - pick any two.

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awneil wrote:

Best; Easiest; Cheapest - pick any two.

I'm defining best for my application as easy and cheap.

 

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What is available for power at the buttons?

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Does it HAVE to be RF, or could IR work as well? Since the range is only 3M, IR could (SHOULD) probably be an option. There are easy solutions for this for under US $10.

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ka7ehk wrote:

What is available for power at the buttons?

 

5V

 

 

 

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mikericetga wrote:

Does it HAVE to be RF, or could IR work as well? Since the range is only 3M, IR could (SHOULD) probably be an option. There are easy solutions for this for under US $10.

 

Haven't completely ruled out IR, but there could be cases where line-of-sight does not exist, including for reflections.

 

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Speed? 10 baud 100 1000 10000 ....

1 or 2 way?

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sparrow2 wrote:

Speed? 10 baud 100 1000 10000 ....

1 or 2 way?

 

1 way, button-pushing baud rate (100?)

 

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If you have 5V, is there no wire connection between the two locations? Where does the power come from at each end? Is either end battery powered?

 

Jim

 

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Take a look at RFM69CW ($3.90 at Ebay).

(Software library for above: RFM69 Library).

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Look like most RF module or IR module will do.
Just had to make sure that this module has 4 output to replace the buttons.

With 5V supply, this module will be able to work or you need to regulate it to 3.3V.

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ka7ehk wrote:

If you have 5V, is there no wire connection between the two locations? Where does the power come from at each end? Is either end battery powered?

It's like adding a remote to a TV or stereo, or a garage door opener.  You can go up to push the buttons, but many users want a little remote for convenience.  So 5V at one end, some kind of key-fob remote, so battery powered.  The device MCU will have the additional pins needed to handle the RX data (all the more reason for a slowish baud rate).

 

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kk6gm wrote:
 I need to replace wired buttons with some sort of RF key fob connection.  All it needs to communicate are signals for UP DOWN LEFT RIGHT APPLY.  Range is maybe 3m max.  So, short range, low data rate.

... and as always, cheap.

RF Digital has 3 button RF keyfobs, long range, low data rate (9600bps UART), coin cell friendly, networks, and not cheap (quality, "expensive").

Could create a 5 button RF keyfob by using an RF Digital module (RFD21733; less expensive at 15USD/one) and a MCU.

http://www.rfdigital.com/

http://www.opensourcerf.com/index.html

 

"Dare to be naïve." - Buckminster Fuller

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How nice does your keyfob need to be?

I have used the remote from a kit with 1 remote that control 3 outlets, all on 433 MHz . Use the transmitter as is, and unsolder the rx radio modules, works fine on 5V about 10-20m (have not tested 3V).

Everything for $15 (and that is included 25% sales tax)
 

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Counterfeit NRF24L01s from ebay are easy to use. I gave up wires.

 

"We trained hard... but it seemed that every time we were beginning to form up into a team, we would be reorganized. I was to learn later in life that we tend to meet any new situation by reorganizing. And a wonderful method it can be of creating the illusion of progress while producing confusion, inefficiency and demoralization." Petronius Arbiter, approx. 2000 years ago.

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Torby wrote:

Counterfeit NRF24L01s from ebay are easy to use. I gave up wires.

+1 for nRF24L01 and nRF24L01+. An excellent balance between cheap and easy.

 

For an even cheaper solution, cosider the ubiquitous OOK/ASK transmitter/receiver pairs. Dumb as a box of hammers, but easy enough to code a link. Adapt an existing library like VirtualWire or RadioHead, or roll your own. Can't beat the price. I'm on my crappy mobile, so searching is sub-optimal, but:

http://www.ebay.ca/sch/i.html?_from=R40&_sacat=0&_nkw=ask+433&_sop=15

 

EDIT: now at real computer, fixed stupid broken link posted from my mobile

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"Fast.  Cheap.  Good.  Pick two."

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Last Edited: Sun. Aug 30, 2015 - 05:10 PM
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Cheapest is to use 433 MHz RF transmitter and receiver modules.

A couple bucks each.

As mentioned above, they do not include any internal signal processing, so the receiver end micro has to look for an incoming valid data packet, and process it.

Easy enough, it just takes a bit more software.

 

Easiest is to use Bluetooth or XBee, but there the cost is higher.

Additionally, XBee is a pretty large physical format, Bluetooth comes in all sorts of shapes and sizes.

A Bluetooth serial port protocol lets you just send data In/Out the USART, it does the error detection and correction for you.

 

JC

 

I made a few comments on 433 modules in reply #13 in this Thread.

 

Additionally:

Note that it is often best to start with the Tx uC USART wired to the Rx uC USART, by wires, and a common Ground, without the RF part installed.

When the hardwired link works well, then insert the RF link, and start to add the error detection software, etc.

 

JC

 

 

Last Edited: Sun. Aug 30, 2015 - 04:42 PM
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Here has some cheap and reliable RF module, also has TX & RX  RF modules.

 

http://www.digirf.com/EN/XWEnRFModule.html

 

*Two of your 3 posts look like SPAM. Be careful because I have my finger on the delete button. Moderator*

Last Edited: Wed. Sep 2, 2015 - 04:11 AM