RF Remote Control

darb1972

Senior Member
Hi All (and particularly Manuka if you are lurking)

I have a client (my Father actually, so this is yet another love job) who wants to turn on/off an Electric Fence Generator using a handheld RF remote control from anywhere on his property. It's not a big property so worst case as the crow flies is around 400m from the Dairy. The location of the transmitter has LOS (Line Of Sight) to most of the boundaries with only two trajectories with another building in the way (around 50m from the Dairy).

I can do experiments if needed as the client is forced to be patient with me (as all Fathers are with their kids :rolleyes:).

I have some older Dorji modules in "stock" so I don't know if they might have the necessary range to do the job. The model is DRF7020D13 (13dBm maximum power). Being in Australia I will need to stick to the 433MHz range and hope I can use sufficient power to do the job. As mentioned, the transmitter needs to be handheld, preferably pocket sized. The receiver can be whatever I like (size/form factor etc) and it can have an omni-directional antenna (basically unity gain) on the Dairy roof. I only need to send some basic code from the likes of an 08M2 to another 08M2. He doesn't need confirmation that it worked because he also has a tester with him that will indicate if the fence is off. That keeps it nice and simple. No need for duplex or running the system in a transceiver mode. Just transmit from the handheld remote the the receiver.

Does anyone know what sort of range I can expect from the models mentioned above? If so, and if these are not considered sufficient (and if I am permitted to increase the power level on our 433MHz band), is there a more powerful Dorji that will do it???

As mentioned, if needed I can experiment, but thought I would run this past the forum first.

Thanks.
 

AllyCat

Senior Member
Hi,

IMHO 400 metres range is quite substantial even in a reasonably "open" environment, with only 13 dBm (20 mW) and a "handheld" transmitter. Also, the 08M2 doesn't have the RFOUT / RFIN commands that might be useful with a "dumb" transmission link.

This sounds like an ideal application for the low-cost HC12 transceiver modules discussed at some length on this forum. Easy to use (ASCII interface) and the user manual talks of 1000 and 1800 metres "open field" range, but that's presumably at full power (20 dBm = 100 mW) and with good antennas at both ends of the link.

Strictly, the power should be wound back a little to be "legal" and hand-held transmitters tend to use a rather inefficient (tuned) loop antenna (because of the 16 cms length and hand-detuning of a quarter-wave "whip"), so I certainly don't consider the HC12s to be "overkill". Also, being a transceiver, it can send "auto repeats" which is transparent to the user but give much greater reliability.

Cheers, Alan.
 

darb1972

Senior Member
Hi All

@ Alan. Thanks for your input (helpful as always) I will take a look at the HC12 modules. I am fairly certain the Dorji modules are very similar in that they aren't "dumb" and probably add a preamble and qualifiers as part of the overall communication package sent to another module. I think they also do a 20dBm model too. I will have to see if I am allowed to transmit 100mW on 433MHz here in Australia. I can put a large whip on the "base" antenna on the dairy, but, trying to keep the handheld remote small will be a challenge. I guess worst case is that if the RF comms at 433MHz proves too difficult, I might need to look at something that might use a mobile phone. That complicates the process so I would prefer to stick with basic RF comms.

You might also be correct in saying that instead of using a basic transmitter/receiver system, I would be best placed to use the modules as transceivers and use, as you say, "auto repeats". By that I gather that you mean that once initiated, the user transceiver will continue to send packages, listen for a response, and either receive a response and stop transmission or possibly timeout after a given period. Was that your intention?

@pxgator Thanks for the link. Very helpful.

@ manuka (Stan). I had a response from you (thank you) that I read earlier whilst on my tablet. Now logged in on my Laptop and I cannot see your response anymore. Did you pull the response or do I have weird stuff happening on my laptop? I won't comment until confirmed as it might cause confusion on the tread if you pulled your response.

Thanks all.
 

darb1972

Senior Member
By the way, who sells the HC12s??? Is it a RevEd product? I would like to purchase these from the appropriate/authorised reseller and NOT from any old (eBay etc) dodgy supplier who might incidentally be selling an unreliable ripoff of the same product (creating even more problems).

Can someone give me a name or a link?
 

inglewoodpete

Senior Member
I bought my HC-12s from an on-shore (Australian) supplier, via eBay, and they have worked reliably for nearly two years. I've had more than enough trouble with cheap FSK modules - my HC-12s work well and I haven't needed to turn their wicks up anywhere near full throttle.

My suggestion is to buy from an Aussie supplier. While HC-12s are probably all made in China, at least an Australian supplier must comply to Australian supplier/consumer law should there be a problem. I prefer to pay the (additional) cost of an ice cream, to have that peace of mind.
 

darb1972

Senior Member
Hi All

@ lbenson. Thanks for the links. I've had a look at his Web Site and also the comments made on "The Back Shed". Indeed, one cannot be too careful when it comes to these things. The last thing I need (and anyone for that matter) is to encounter avoidable issues when in the prototype stage. I'm not a dog and therefore don't enjoy chasing my own tail! ;). Thanks again for the heads up!!!

@ Pete. Thanks for the comments. Can you recall who you used for your purchase? I have to admit that when it comes to purchases on eBay, the whole thing is somewhat confusing and misleading. By that I mean suppliers can tend to mislead you by flying the Australian Flag whilst not even being located in this Country. I am not even certain if the search filters remove all that aren't Australian. I would appreciate it if you could give any further details.

Grog's site also lists a reasonably priced test/programming jig that might come in handy. Does anyone know if this is a standard/factory jig or is it an item someone has developed to support the HC12s???
 

inglewoodpete

Senior Member
@ Pete. Thanks for the comments. Can you recall who you used for your purchase?
I archive all my on-line purchase emails. I would have posted the supplier ID but they are no longer trading. Ebay does show where the item is located. Look for the "Click and collect" option, although I have not used this service.

Grog's site also lists a reasonably priced test/programming jig that might come in handy. Does anyone know if this is a standard/factory jig or is it an item someone has developed to support the HC12s???
This item by PhilHornby is a good place to start. Initially, it was what I used but I moved on to a 20X2 with its background serial reception.
 

lbenson

Senior Member
Grog's site also lists a reasonably priced test/programming jig that might come in handy. Does anyone know if this is a standard/factory jig or is it an item someone has developed to support the HC12s???
So far as I know, Grogster designs all of the PCBs on his website (except for the HC-12s), sometimes in collaboration with others. Good stuff, intended to be reasonably priced and to "just work".
 

techElder

Well-known member
Darb1972, since you have a barn which presumably has a high peak, I would create repeating device for the remote keyfob your father will carry around. That will remove the smallness problem and certainly increase the range.
 

manuka

Senior Member
Darb1972: Re that fleeting response. I'd deleted initial thoughts after reflecting on a past (non Forum) saga from a dry area Queenslander that -sigh- became tediously lengthy... About a dozen emails in it transpired his so called "block" was a sprawling & commercial outback spread of ~8000 hectares, with distances of ~20km to span!

I eventually pointed him to an Australian commercial crowd that use the Aus/NZ PRS Ch.22/23 UHF CB data spots. Up to 5W transmitter power is permitted on these,which naturally gives superior punch compared with our 25mW legal maximum on 433MHz. Even so repeaters may indeed be needed...

OK on your one way need, but maybe clarify issues such as terrain, nature of stock, frequency of operation,nature of the e-fences electrics/electronics & even how it's powered (solar ?)

Aside from these I've concerns that your "electric fence generator" may produce RF interference to ASK control devices. (FM tends naturally immune). I grew up in rural NZ & well recall the irksome broad band pulses that could often arise from neighbouring e-fences.

FWIW the cheap CMOSTEK based 433 MHz RX modules sold by HopeRF have shown themselves to be great performers in noisy RF conditions- refer their Forum mention Nov.2017.

EXTRA: Given the nature of the demanding & often dirty outdoors,along with "senior issues" using today's technology, I'd suggest organising a very rugged & reliable approach. How about training a super smart Border Collie to race down the paddock & flick a switch !?
Stan.
 

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Pongo

Senior Member
In view of the distance and nature of the system I would want a two way system so there's feedback as to whether it did actually switch. Something like a heartbeat transmission from the remote unit when the fence is energized.
 

mushroom

New Member
Hi all. I've used 6 x HC-12's on 6 poles with solar charged batteries to control signs that warn of animal training in progress. Signs are huge printed signs with two single 12v traffic lanterns each that alternately flash once per second. All controlled by one transmitting HC-12 on a shed. Further most pole is over 700 mts from the tranmitter with no feedback. They turn on at 3am and off at 9am, timed by on board real time clock in the transmitter end controlled by a picaxe 20 X2. Proven reliable over 8 months. Antenna's are $6 Ebay units. All receivers are controlled by Picaxe 20m2. (same board as transmitter, but without the RTC Installed). Operated at legal power for Australia. If helpful I can give some detail when I'm at work and the boss is not. (He prefers me to be doing his work). Can't answer at home as I'm a Dad taxi for my 10yo, 11yo and 12yo kids. I'm a 60 yo. (Extra maths classes, Drum lessons, graphical 3D and coding classes, Autism assistance classes. Four people in my house and one of my sons is different in that he is not autistic).
 

darb1972

Senior Member
Hi All

Sorry, been working long hours. Thanks for the responses.

@Tex. Totally agree. The Shed/barn (all metal/iron construction) will no doubt cause an RF shadow. It could act as an RF hop/repeater location.

@ Stan. Not trying to cover that kind of area!!! The terrain is totally flat. Very few trees. No buildings beyond a house and a shed/barn. Stock is not big in numbers (might only be a couple of dozen scattered stock). By frequency of operation do you mean actual frequency or use? It wouldn't get used too often. Maybe once a day (at the most and at a guess). The Electric Fence system is mains driven. As mentioned, generally Electric Fences tend to produce wide band impulse noise IF there is a fault with the fence line and/or a short to ground (even from a blade of grass). You can use an AM Radio to locate issues (as the impulse noise increases as you approach the issue). Hard to say if the impulse noise would cause issues with 433MHz. Would have to experiment. I know that it can cause issues with the lower end of the VHF band (around RF Ch6 to at least Ch10). Beyond that I am not certain if it has an impact. Could produce harmonics. Not sure.

I'll have a look at the RF Hope units. Dad has a dog. She's really smart, but not that smart!!!

@ Pongo. I think that's a good idea.

@ Mushroom. Thanks for the information. Without getting you fired, I would be interested to hear more about your system!!!
 
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