Author Topic: Transmitter/Receiver Pair  (Read 1189 times)

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Offline sherbyTopic starter

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Transmitter/Receiver Pair
« on: July 27, 2013, 05:25:42 AM »
Is there a particular way to hook up
OR
Is there a transmitter/receiver pair out there only for digital transmission?
Purpose is that if there is a digital HIGH(5v) at the input/signal to transmitter, then there should be a high at receiver output?

Thanks for any help!


Offline jwatte

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Re: Transmitter/Receiver Pair
« Reply #1 on: July 27, 2013, 12:54:46 PM »
I assume you mean wireless transmitters? Because wired transmitters would be very easy for that situation :-)

The Xbee series can be configured to forward the state of its digital pins. If a pin goes high on Xbee A, Xbee B will drive that same pin high. It is a 3.3V device, though, so you have to also add a voltage level shifter.

Offline sherbyTopic starter

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Re: Transmitter/Receiver Pair
« Reply #2 on: July 28, 2013, 06:39:51 AM »
Is there a smaller sized wireless transmitter, that can achieve the same?
i Just need a small transmitter, the size of receiver does not matter.

Thanks

Offline johnwarfin

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Re: Transmitter/Receiver Pair
« Reply #3 on: July 28, 2013, 10:13:13 AM »
contrary to ads small/cheap 433mhz ook tx/rx pairs are unable to transmit on/off type data like rs232 reliably due to modulation and dc offset issues. so what you put in does not always resemble what comes out.

as j points out digital transceivers are the trend these days. however xbee are extremely expensive and not very small. at about 1/10th the cost and 1/5th the size, newer 24l01 or 7105 based modules are the way to go. although prices are creeping up they still go for around a buck or so on places like ebay, aliexpress, and dealextreme.

Offline jwatte

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Re: Transmitter/Receiver Pair
« Reply #4 on: July 28, 2013, 10:18:48 AM »
Yes; the main benefit of Xbees is that they Just Freakin' Work (tm)!

If you need shorter distance, lower protocol, lower interference resistance, and smaller size, then you could go so far as to use a simple AM chip for a few square millimeters plus coil.

A typical nrf21 module isn't much smaller than an Xbee (and is also 3.3V): http://imall.iteadstudio.com/wireless/im120606002.html

An AM transmitter can be smaller: http://imall.iteadstudio.com/wireless/im120628014.html
Note that the ASK used by that AM module isn't particularly robust. But it gives you exactly "high in -> high out" behavior when it works, and the encoder is a little smaller than an Xbee.
There's also a 315 MHz version if you're in a jurisdiction where that is an acceptable frequency and/or 433 is not.

Offline jlp

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Re: Transmitter/Receiver Pair
« Reply #5 on: August 01, 2013, 09:29:06 AM »
You can buy online 433mz transmitter and receivers for cheap, couple of dollars. These are useless unless you also buy the encoders/decoders to go with them, again a buck or so. The encoder I use is a PT2262-M4, the decoder I use is the PT2272-M4. This enc/dec can be hard wired to a specific address something like a garage door opener. So you can have one receiver and make it address switch selectable (dip switch, or by a micro-controller) to control multiple receivers which have there own address running at 433mz. They work from 3vdc to 15vdc.

Offline MrWizard

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Re: Transmitter/Receiver Pair
« Reply #6 on: August 03, 2013, 02:24:59 AM »
You can buy online 433mz transmitter and receivers for cheap, couple of dollars. These are useless unless you also buy the encoders/decoders to go with them, again a buck or so. The encoder I use is a PT2262-M4, the decoder I use is the PT2272-M4. This enc/dec can be hard wired to a specific address something like a garage door opener. So you can have one receiver and make it address switch selectable (dip switch, or by a micro-controller) to control multiple receivers which have there own address running at 433mz. They work from 3vdc to 15vdc.

Good info. Thanks.

Offline sherbyTopic starter

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Re: Transmitter/Receiver Pair
« Reply #7 on: August 18, 2013, 11:26:00 PM »
thanks for the reply guys.
Also john, can you post a link to the  24l01 or 7105 based modules  , i couldnt find anything about them online.
Thank You

Offline johnwarfin

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Re: Transmitter/Receiver Pair
« Reply #8 on: August 19, 2013, 03:05:42 PM »
thats hard to believe. a quick search will show pdfs available from the mfg and many available on ebay for a dollar and change ea shipped. i just got over a million hits with google. and on ebay for example:

http://www.ebay.com/itm/1X-NRF24L01-2-4GHz-Antenna-Wireless-Transceiver-Module-For-Microcontroller-EA-/231025336369?pt=Power_Cables_Connectors&hash=item35ca2ee031#ht_5691wt_1136

dealextreme, aliexpress, goodluck, etc have those and 7105 for even less. ive gotten transceiver modules like these for as little as half buck (might need to buy a few). strangely the chips themselves run about 2x more. go figure. im surprised you were not able to locate these deals. only takes me a minute or two to hunt them down.

there are units available with 100x higher power output too like rfm22b. in any case all these digital modules have much better range and data integrity than cheapo ook type which, these days, arent so cheapo after all. in many cases now they cost more than the digital ones.

ive had considerable experience with all these devices so if you have any specific hardware or software questions dont hesitate to ask.
« Last Edit: August 19, 2013, 03:22:44 PM by johnwarfin »

Offline jwatte

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Re: Transmitter/Receiver Pair
« Reply #9 on: August 19, 2013, 11:16:01 PM »
Quote
there are units available with 100x higher power output too like rfm22b

Isn't that strong enough to actually need licensing even in the ISM band? And/or might not even be approved for ISM usage?
(That kind-of depends on what the 100x is in comparison to :-)

Offline johnwarfin

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Re: Transmitter/Receiver Pair
« Reply #10 on: August 20, 2013, 09:02:18 AM »
power limits are not the same for all ism bands. here in usa up to 1 watt is allowed for radio control at 2.4ghz. rfm22b is 100mw and 24l01 is 1% of that at 1mw so both well under the limit. even the rfm23bp at 1watt is technically legal but has other issues making it less desirable.

as a radio amateur im a fierce advocate of proper band usage and get quite upset at some of the abuses. overpowered tx are common in my area. not only illegal but quite rude to others who share the airwaves. pirate fpvers, using what i estimate to be 30-40 watt wifi boosters, often prevent me from enjoying milliwatt range video robot plane experiments. even though they may be in the next county. i wish there was something i could do about it.

Offline jwatte

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Re: Transmitter/Receiver Pair
« Reply #11 on: August 20, 2013, 10:41:06 AM »
Quote
i wish there was something I could do about it

You can report to the FCC. You can get a direction sensor to try to get more of a lock on the signal.
It's unlikely they will do something from one report, but if there are multiple reports, they should start taking action, as that is their job.

Offline sherbyTopic starter

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Re: Transmitter/Receiver Pair
« Reply #12 on: August 23, 2013, 11:23:10 AM »
Thanks for all the help, also as there seems to be no small or SMD sized pair,  is there a programmable transmitter/receiver pair out there that anyone is aware of?
I guess i could do the digital data sending(High-LOW), through something like that.

Offline waltr

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Re: Transmitter/Receiver Pair
« Reply #13 on: August 23, 2013, 04:58:17 PM »
How about these from Adafruit:
http://www.adafruit.com/products/1095

Offline sherbyTopic starter

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Re: Transmitter/Receiver Pair
« Reply #14 on: August 23, 2013, 06:30:44 PM »
Actually that is exactly what i am looking for.
Thank you waltr for pointing it out, and thanks everyone for your inputs!

 


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