Radio Modules

[Hooter]

I am about to purchase a couple of radio transceivers from
http://www.futurlec.com/Radio.shtml - the last module in the list -
Transparent Wireless Data Link 433Mhz-Rs232. Have any of the radio buffs
on this forum used these before or have any comments on their suitability
when coupled to Picaxes.
Any responses will be appreciated.
Hooter

 

[manuka]

Not exactly THAT one, although many of those listed at the site look akin to diverse others that I've tickled over the years.

However this configurable HM-TR433 transceiver certainly looks interesting & the firm ( HOPE- Shenzhen-China's manufacturing region over border from HK) have certainly done their homework on this it seems. I'd be interested in having a play with them myself, the least reason being their combo tx/rx would make half duplex & error correction a breeze. 433 Mhz ISM offerings are overdue for a 2nd generation approach, the least of which should be better use of that ~1MHz wide spectrum I'd say.

Mmm- the Hope .pdf data shows that although a puny transmitter, this HM-TR433 unit seems pretty sensitive (-109dBm !),with ranges likely to be 300m or so- maybe even 1km with "cotanga" Yagi antenna each end. But I'd only believe it when field tested. All manner of claims are made for these cheap ISM units & some are pretty unjustified I've found.

Spill the beans. Why spend that sort of $$ for the extra features, as even 433 MHz cheapies ($) PICAXE drive beautifully. IF you are trying to setup a demanding link ( come in Dr_A) then you'll need more transmit power I'd say. What are you trying to do? Stan

 

[Hooter]

Manuka

I have been looking at making a local network (along with everyone else) for the house and garden. I have played with the Jaycar TX and RX as a transceiver and they work well. I considered the Hope units as they looked easier to communicate with - from Picaxe to Transceiver etc - and comms between transceivers was already taken care of. Nothing sinister. Cost worked out about the same as the Jaycr Rx and TX together and this module would be easier to mount etc.
Hooter

 

[moxhamj]

I'm going to write up my experiments properly with photos in the next day or so. Ideally it would be great to have some comparisons with other modules based on real world experiments. I agree with manuka that the only way to compare units is with experiments. My conclusions so far is that real distance with trees/wet ground/plants/the odd metal stake/shed/house etc is about 1/4 to 1/8th the distance claimed.

Am actively experimenting with solar charging systems at the moment doing field tests on detecting overcharge states by measuring battery temperature. Remote units ought to need infrequent servicing - ideally for several years.

109dbm is the same as the superhets I have been using. The superregen's were 93dbm. The extra db will make a difference to range and it probably is better to go for extra Rx sensitivity before going for higher Tx power.

 

[manuka]

Dr_A ... add to your list endless SA heatwave days too it seems. How ARE you guys coping with daily temps in the 40s? Shades of Ash Wednesday ( Feb. 16th 1983) ...

HopeRF are offering free samples => http://www.hoperf.com/order.asp , & so I for one will hereby put up my hand. If these little HM-TR433 darlings measure up we may even be able to get some decent direct imports organised. Naturally we'll need 2, so how about Dr-A & I organise a LOS TransTasman link. Stan

 

[moxhamj]

Yes it is a bit warm. Minimum at night is 31C. On the plus side, I am doing experiments on detecting when a rechargeable battery is charged and the hot temperatures are pushing things to the limit. I have one LM35 in free air and another taped to the battery with the battery wrapped up in some foam insulation. My dad was horrified - "you can't wrap up a battery in insulation - it will overheat!"

But what happens is that with a 300mA charge the temp only goes up by 1C when charging, then very quickly goes over 4C when charged. This can be used to detect the overcharge state so the battery never overheats. And it has been quite useful to see if this temp differential works ok over large changes in ambient temperature, especially with ambient temp over 47C in the shed. A 14M is in charge of the power supply and does the stepup from 1.2V to 9V, handles the overcharge detection and shorts the solar cells when charged, plus senses that the 5V supply for the picaxe is stable.

Once that works I'll be pairing it with an 08M that uses whatever radio module works the best. Maybe I'll get a sample as well from futurlec.

 

[manuka]

Ok- samples however are NOT from Futurelec, but direct from the Chinese makers HopeRF. How about I ask for a pair (for which I'd do a SC review) & then send them on to you? Stan

 

[Hooter]

I too have requested a pair - will see what happens. If I don't get any joy from Hope
I will get a couple from Futurlec and have a play.
Hooter

 

[moxhamj]

*cough cough* "Hooter has requested a pair", but may not "get any joy from hope." The double entendres are worse than an episode of "The Two Ronnies"

I have written up the 500 metre data link experiment at http://www.instructables.com/id/Build-a-500-metre-radio-data-link-for-under-40./ with a link in the forum's completed projects. The last piece of the jigsaw was a proper balun - now it goes over a hill! Next step is to get the solar power supply working.

 

[Hooter]

Dr_Acula

Shame on you Dr_Acula. Hooter was a nickname I acquired years ago in reference to the fact I play the Saxaphone. Sorry but I couldn't help myself with the Hope-Joy effort.
Hooter - (Singular)

 

[manuka]

Dr_A- bravo on that Instructable, but suggest we try to direct this datacomms topic into just a single Forum posting. Along with you 2 pundits, I'm also "Hopeless" at present, but anticipate significant mileage when/if they arrive for a workout. Stan

 

[manuka]

Hooter et.al - any joy yet with those HopeRF modules? They've not responded to may requests... Stan

 

[Hooter]

Manuka

They arrived yesterday morning. Dispatched from Hong Kong on the March 30, arrived April 02 - not bad. I will be having a play with them over the weekend. Cost $10 USD each including rubber duck aerial. $20 USD DHL freight. Standard freight price of $20 USD for up to 30 units.
Hooter

 

[manuka]

Hooter- thanks for the update (& personal email). Since you've a pair in your hand guess I'll wait your feedback before ordering myself. Stan

 

[moxhamj]

I'd be very interested in any range tests you can do

 

[Hooter]

Is there any particular method or format you gentlemen would like me to use - in the name of consistency. I have 08M's and 14M's at hand.

 

[manuka]

Hooter: Most thoughtful of you to ask! In the name of simplicity I suggest a 08M each end sending code to keep an LED on at the far end when the signal is received correctly. Tests of their LOS range, especially in "noisy" environments, & ability to punch thru' a few trees & buildings would be welcome too. The major weakness of many cheapie 433 setups relate to their pretty deaf receivers I've found, & these Hope units look most promising in comparison. Stan

 

[manuka]

Hooter- 5 days later- any joy with the HopeRF units? Stan

 

[MFB]

Low cost with integral FSK modems

Farnell in the UK have introduced a new 433MHz FM transmitter/receiver pair (order codes 151-7426 and 151-7427 respectively) for about £10. The interesting thing about these Quasar products is that they have integral FSK modems. Farnell claim transmission rates of 4.8kbps over 200 metres, when operating from a 3V supply.

I have not yet tried these units but have added FSK modems to other basic low power 433MHz links to achieve robust data communication under very difficult operating conditions. This was using ‘standard’ serial UART communications code, without the need to add preamble or mark: space balancing techniques etc.

The above Franell units should therefore give good range performance when working directly with PICAXE serial ports/code.

 

[manuka]

Good find. However these are also handled directly by QUASAR UK=> www.quasaruk.co.uk/acatalog/FM_Transmitter_Module.html , & although FSK look to have performance & pinouts akin to many existing offerings.

IMHO the wireless data field is ripe for 2nd generation 433 ISM units, especially making better use of the ~1½MHz spectrum slice available. Regs limit to 25mW tx power so the best range & reliability boosting approach is probably via better receivers- some ASK offerings have sensitivities just ~ -94dBm & are pretty deaf! Each 6 dB improvement will double range of course, so a -106 dBm sensitivity will have 2x2 = 4 times the range. With 6dB Yagi each end this may lead to yield point to point LOS ranges of km.

I remain a fan of 433MHz for PICAXE work, as signals at this UHF freq are not as prone as 2.4GHz to LOS obstruction & simple antenna are readily organised. There are often so many other powerful 2.4GHz sources - Bluetooth, ZibBee, AV baby monitors, cordless phones, WiFi APs, & leaky microwave ovens etc - that weak signals at this higher band may be swamped. Stan

 

[Hooter]

Preliminary range tests

Finally got time to do some testing of the Hope-RF transceivers. In open air and on a metre high wooden pole and with the accompanying 6 inch rubber duck aerial they worked reliably up to 150 mtrs. This was sending data at 2400bd twice every second to flash an LED.
They worked perfectly indoor and outdoors all over our 1050 sq/mtr/block/section (Aus/NZ).
From inside the house they worked perfectly 75 plus mtrs down the road with the houses and trees in the transmission path - out of 'line of site'. May have gone further but ran out of houses.
I will do further testing while using RT's and mobile phones in close proximity when time permits.
Hooter

 

[manuka]

Great! I eagerly await your walkabout tests- perhaps drive to an open field etc & place the tx on your car roof while walking away with the rx. I already sense you'll be good for a LOS km!