Is HopeRF module still recommended?

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inglewoodpete

Senior Member
Some members may have seen my comments and questions in the recent rfout and rfin thread.

While I am happy with the cheap ASK modules with rfout and NKM2401 for receiving (especially the >95% reliability with superhet receivers), for my purpose the loose wire 1/4 wave antennae for both send and receive modules are very untidy. In my search for alternative superhet ASK receivers, I found these HopeRF HM-TR on Futurlec's website. A transceiver with just one antenna: better still, a 'proper' one!

I see that the HopeRF HM-TR modules first appeared 7 or 8 years ago and know that technology moves fast. While not cutting-edge any more, do they still do a reasonable job compared to more modern units?

My project is to a create wireless link between my car and my house to report the locked/unlocked/absent status of the vehicle. The maximum range for the link would be about 20m from inside my house to my car.

The reason being that (very) occasionally, either my wife or I manage to leave the car unlocked in the driveway (we do not have the luxury of a lockable garage). We usually 'get away with it': discovering that we failed to lock the car on the following morning. We don't live in a bad area but a few months ago woke to find some of the doors open and a few items stolen. Fortunately no damage to the car but it cost a couple of hundred dollars to replace my tool kit etc.:( The wireless link would provide us with peace of mind that we have not left the vehicle unlocked.
 
hippy

hippy

Technical Support
Staff member
I can't comment on Hope modules but when I was using my dumb modules I found they worked well and looked good with solder-tag 'rubber duck' helical aerials connected to them with a short flying wire, especially the 'stubby' version. We tested a variety of such aerials with our RFA001 modules and they all seemed to work well though not exhaustively tested.

Another trick is to use heavier wire and build your own helical aerial. Coil that around a pencil and put a rubber tube around it. That's what's commonly done with PMR radios and cheaper 'toy' walkie talkies.
 
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manuka

Senior Member
Back in 2009 I penned a SiChip article on these,but the likes of the HC-12 would now be a more obvious (& cheaper) choice. For a mere 20 metres range you may even get away with WiFi/BT - or even optical (IR ?) /audible?

However - given that late model cars are tending too smart for themselves - how had you intended interfacing with the car's locking system ?! Stan.
 
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inglewoodpete

Senior Member
manuka said:
Back in 2009 I penned a SiChip article on these,but the likes of the HC-12 would now be a more obvious (& cheaper) choice. For a mere 20 metres range you may even get away with WiFi/BT - or even optical (IR ?) /audible?
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I had read that article and became further enthused but the picaxe.orcon.net.nz or picaxe.orconhosting.net.nz sites, which hosted a wealth of your knowledge, appear to have gone. Do the orcon-hosted pages appear elsewhere today? Regardless, I'll look further into the HC-12 transceiver.

My problem is that I'm already on a steep learning curve and one can buy and test dozens of wireless solutions. I would like to condense some of your 50+ years experience into the next few months :).

Some of your alternative methods offer potential. Due to the fact that the vehicle may be located in the drive-way (forwards or backwards) or on the street or street verge (berm in NZ - love the terminology:)), optical or audible are probably not going to work. I have considered other wireless options but few offer low-power modules. I don't want to flatten the battery if the car stands idle for a few days.

manuka said:
However - given that late model cars are tending too smart for themselves - how had you intended interfacing with the car's locking system ?!
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I am looking into a couple of methods. One is to monitor the driver's door-lock lines, probably with opto-isolators, and have the PICAXE record the last action. The other is to monitor the CAN bus and, again, record the latest door-lock activity. I'm not phased by either method. Obviously, the latter method would take a lot more coding.

PhilHornby said:
Maybe you did lock the car :( https://www.wired.com/2016/08/oh-good-new-hack-can-unlock-100-million-volkswagens/
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At least we'd know about it! No, I don't have a Volkswagen.
 
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srnet

Senior Member
Be carefull putting a transmitter in a vehicle, it can interfere with the vehicles own central locking, preventing it from working.

On more than one ocaision I have been unbable to get in to my own vehicle, as I had left a UHF transmitter running in my pocket.
 
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inglewoodpete

Senior Member
Aware of that one. The vehicle's transmitter would only be enabled to report a lock or unlock event or when responding to a periodic poll from the (house) base unit. Similarly, the base unit would only be enabled when polling the vehicle's status, normally for a few 10s of milliseconds every few minutes.
 
hippy

hippy

Technical Support
Staff member
inglewoodpete said:
I am looking into a couple of methods. One is to monitor the driver's door-lock lines, probably with opto-isolators, and have the PICAXE record the last action. The other is to monitor the CAN bus and, again, record the latest door-lock activity. I'm not phased by either method. Obviously, the latter method would take a lot more coding.
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I would personally start by considering a long arm microswitch which could be used to determine if the door plunger were down or up.

They are available with SPDT configurations, easy to wire, should have no potential for interference with existing circuitry or electronics and can be used to only power the warning system when actually unlocked. Being 'if I am on the car is unlocked' makes programming a breeze.
 
PhilHornby

PhilHornby

Senior Member
Door Lock/Unlock detection

inglewoodpete said:
I am looking into a couple of methods. One is to monitor the driver's door-lock lines, probably with opto-isolators, and have the PICAXE record the last action. The other is to monitor the CAN bus and, again, record the latest door-lock activity.
Click to expand...
Assuming the Central Locking control module flashes the indicators on Lock/Unlock, maybe you could make use of that signal? (The only other time left and right indicators are powered together, being when the Hazard Warning lights are activated). If nothing else, the indicator wiring is probably more accessible.
 
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manuka

Senior Member
A quick Google shows assorted lock state ideas - see here. Alert - be very wary of car direct electronic "attachments",the greatest concern being of course SAFETY. Insurance issues may also arise, as even the smallest non standard automotive tweak may lead to a claim being declined...

PhilHornby's optical flash sensing device may have merit however?

Inglewoodpete: Apologies - sorry for the now dead links at "picaxe.orcon.net.nz". I naturally still have all this material if you want it.

{Muse mode} Much of my past enthusiasm related to decades of e-teaching work, and upon retirement a lot of my e-activities have been wound down to favour more durable pursuits! The recent $amsung Note 7 $orry $aga typifies the distre$$ingly withering pace of today's electronics I'm afraid. Go to whoa in 8 weeks,along with a US$4 billion loss... Stan.
 
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inglewoodpete

Senior Member
Refocussing on the subject of wireless data comms, particularly transceivers; the HC-12 seems to be more prevalent this days. Most HC-12s, if not all, seem to have a tichy little u.FL/uFL/IPX/IPEX male coax connecter on-board. I have discovered that there are a number of uFL-to-SMA patch cables available. The panel-mount SMA socket paired with a 433MHz quarter-wave 'rubber ducky' antenna makes for a very neat solution. I think that is the path to follow - the spiral wire antennae are handy on the bench but not very pretty out in the world.

@manuka - you may have been distracted by the off-topic discussion but are your previous orcon hosted website contents still lurking about somewhere in the ether? In particular, the page/s on HopeRF? Edit - sorry Stan, I only noticed your post on this new page after posting this one. I'm sending you a PM.
 
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manuka

Senior Member
inglewoodpete: OK - I'll PM you.

The HC-12's onboard antenna socket offers antenna access that'd be tending overkill. The module is capable of 100s of metres using just that dinky spiral! For your modest needs of ~20 metres you could almost hide ths spiral somewhere away in the box - or even just use a ~170mm flexible wire.
Stan.
 
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Jeremy Harris

Senior Member
manuka said:
The HC-12's onboard antenna socket offers antenna access that'd be tending overkill. The module is capable of 100s of metres using just that dinky spiral! For your modest needs of ~20 metres you could almost hide ths spiral somewhere away in the box - or even just use a ~170mm flexible wire.
Stan.
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I can confirm that. I've used the uFL to SMA cable plus a small rubber duck antenna and it is indeed overkill for most applications. It does increase the range a fair bit, but if you're only looking for 50m or so of range the small coil antenna is more than adequate. The range with a decent 1/4 wave whip antenna is of the order of 100's of metres at low baud rates.
 
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inglewoodpete

Senior Member
Jeremy Harris said:
I can confirm that. I've used the uFL to SMA cable plus a small rubber duck antenna and it is indeed overkill for most applications. It does increase the range a fair bit, but if you're only looking for 50m or so of range the small coil antenna is more than adequate.
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I've ordered a couple of HC-12s with the coil antennae included and will experiment with their range when they arrive in a couple of weeks. ~170mm of trailing wire or an exposed coil will not suit my requirement. If I can hide them, so much the better. However the steel body of the car could act like a faraday shield. Time will tell. It would be good if I could 'turn the wick down' on the transmitters.
 
PhilHornby

PhilHornby

Senior Member
inglewoodpete said:
However the steel body of the car could act like a faraday shield.
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I've had them in the car (and also inside a freezer), to give them the severest test I could think of (for my application). Nothing seems to affect them. I've not used anything other than the spring 'thing' that's supplied with them. (Given that I use them on 458MHz, rather than 433MHz, the spring is probably not the optimum length).
 
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