RF w/434 mhz sparfun pair and LCD

alistairsam

Senior Member
Hi,

I just got a 434Mhz RF Transmitter receiver from sparkfun and am having trouble receiving transmitted data.

http://www.sparkfun.com/commerce/product_info.php?products_id=8946

http://www.sparkfun.com/commerce/product_info.php?products_id=8950


I have searched through this forum, and am using the "precondition" transmit and pause as suggested, but still don't receive what I'm transmitting.

i'm using two 20x2's, one for the transmitter and one for the receiver.
I have soldered a 17cm long wire to the transmitter as suggested, and no antenna in the receiver. they're 1m apart.
receiver has a 16x2 LCD that I want to display the received data on.

if I don't use qualifiers at the receiver, it outputs numbers randomly which I presume is noise.

am I doing this correctly?

Code:
'TRANSMITTER

#picaxe 20x2

let dirsB = 00000011


main:
for b0 = 0 to 240 
serout B.0, N2400_16, (0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55)
pause 5
serout B.0,N2400,(b0)
sertxd (#b0,CR,LF)
pause 300
next b0 ‘ next loop
goto main



---------


' RECEIVER

#picaxe 20x2

let dirsB = 00000011


main:
serin C.0,N2400_8,b1
pause 5
serout B.0, T9600_8,(254,128,#b1)
pause 300
goto main
 

lbenson

Senior Member
Your code has the "conditioning" 0x55, but no qualifiers which help the receiver to latch onto the transmission out of all the noise.

Try sending something like "ABC" before the b0, and then receiving with

serin C.0,N2400_8,("ABC"),b1

Check out manual 2 for serout and serin.

I have successfully used the sparkfun tx & rx, tho the 315mHz version because of the 433mHz noise in my locale.
 

manuka

Senior Member
IMHO you can't beat having a simple 433 MHz receiver at hand to verify signals actually ARE being sent. At slow baud rates changes can even be "heard" as well. This furthermore will often reveal all manner of local interference you'd never considered !! Failing a UHF scanner perhaps check the Jaycar module approach I rustled up.
 
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alistairsam

Senior Member
Your code has the "conditioning" 0x55, but no qualifiers which help the receiver to latch onto the transmission out of all the noise.

Try sending something like "ABC" before the b0, and then receiving with

serin C.0,N2400_8,("ABC"),b1

Check out manual 2 for serout and serin.

I have successfully used the sparkfun tx & rx, tho the 315mHz version because of the 433mHz noise in my locale.
Hi,

I tried the following, but still no luck
Manuka, I don't have a transistor or piezo, so will try your circuit when I get them.

Code:
' RECEIVER

#picaxe 20x2

let dirsB = %00000001
let dirsC = %00000000

serout B.0,T9600_8,(254,1)

main:
serin C.0,N1200_8,("ABC"),#b0
serout B.0,T9600_8,(254,128,#b0)
pause 300
goto main





'TRANSMITTER

#picaxe 20x2

let dirsB = 00000011

let b0 = 112

main:
toggle B.1
serout B.0, N1200_8,(0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55)
pause 5
serout B.0,N1200_8,("ABC",b0)
pause 100
goto main
does the "pause 5" have to change as the 20x2 is at 8Mhz.

when I transmit text, how do I enter it as ascii into variables and display to the LCD? is it just using # as above?

also, does the serout have to be N instead of T?
 
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alistairsam

Senior Member
I finally got it working, but strangely enough, presence of a human body makes a big difference. I had the transmitter and receiver on either ends of my bench, more than 1m apart, but for some reason, when I'm in the middle, it works fine, when I move away, it does'nt receive data with the qualifier.
I'm using a 17cm wire as antennae on both rx and tx.

other thing was the code. I had a 300ms pause at the receiver to refresh the lcd, and then get serin, apparently that was not quick enough.
i therefore removed the lcd refresh to a subroutine, and it then worked

need to figure out LCD refresh using the settimer, as I can then refresh the LCD independently 4 or 5 times a second, whether data has been received or not.


Code:
'TRANSMITTER

#picaxe 20x2
setfreq m16

let dirsB = 00000011


main:
for b10=0 to 240
serout b.0,N4800_16,(0x55,0x55,0x55,0x55,0x55,0x55)
pause 5
serout b.0,N4800_16,("XYZ",b10)
next b10
goto main


' RECEIVER

#picaxe 20x2
setfreq m16

settimer t1s_16

let dirsB = %00000001
serout B.0,T9600_16,(254,1)


main:
serout B.0,T9600_16,(254,1)
do
for b5=0 to 3
serin c.0,N4800_16,("XYZ"),b10
if b5=3 then gosub displ
next b5
loop


displ:
b5=0
serout B.0,T9600_16,(254,1)
serout b.0,T9600_16,(254,128,#b10)
pause 5
return
I need to stream continuous numbers to the receiver, so will need reliable comms. not sure if the antenna will make a difference.
the qualifier also made a huge difference.

How do I use a 9V supply to the transmitter, but 5V to the picaxe? I'm using a 9V battery to a 7805 regulator and then to the picaxe and transmitter, but if I connect the transmitter to the 9v battery, and its data to the picaxe output, and power the picaxe through the 7805 regulator, will that cause issues? do I need to use another regulator or diode for the transmitter?
 
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MFB

Senior Member
The problem could be that the transmitter and receiver are too close and the latter is being overloaded. Try a bench test with only the transmitter antenna connected.
 

NXTreme

Senior Member
I have found the SparkFun 315 MHz TX/RX pair very easy to use. I did notice one thing though. When I used the suggested quarter wave-length antenna (~23 cm) I stopped getting reliable data after about 50 meters. I changed that to a half a wave-length and got 95% reliable data at 450 meters! That's three times longer than specified! I live in an area where there is little to no interference though, that makes a big difference too.
 

alistairsam

Senior Member
The problem could be that the transmitter and receiver are too close and the latter is being overloaded. Try a bench test with only the transmitter antenna connected.
I tried moving the transmitter to the adjacent room with both antennae, no data, kept it back at the bench with 1.5m distance, but no antenna on receiver, no data.
soldered the 17cm antenna back, unreliable link.
one of the sheets for this pair mentioned using 9v or 12v for the transmitter.
am just a bit wary of connecting 9v to the transmitter, but using the same 9v for a 5v regulator and then the picaxe, as the picaxe output pin is directly connected to the data pin of the transmitter.

Nxtreme, did you use 5v for the transmitter? I might get the 315Mhz modules as well.
 

hippy

Technical Support
Staff member
From the first link - "If you can configure the UART module on a PIC, you have an instant wireless data connection". That suggest a Txxxx baud rate should be used.
 

NXTreme

Senior Member
Nxtreme, did you use 5v for the transmitter? I might get the 315Mhz modules as well.
No, I used three AAs for the transmitter and a 9V battery regulated down to 5v for the receiver. I'm dual-booting, otherwise I'd give you the code (it's on the Windows partition, I'm on Linux right now). Next time I boot up Windows I'll post the code. I used two 08Ms and I suggest you do too if you want to keep it simple. Get it working simply at first, get more advanced later. I do suggest the 315Mhz modules just because you will most likely have less interference using them instead of the 433Mhz variety.
 

geoff07

Senior Member
The data says that the tx accepts digital (aka TTL, 5v) inputs so connecting the tx to 12v should be fine. The more juice to the tx the better. Do it via a protection resistor if you are concerned, 350 ohm should be enough. (12-5v=7 at 20mA = 350). 390 would be the nearest but almost any up to a few k would probably work, or even higher.
I use a different make of similar rx/tx and don't use a resistor.

Key thing about the baud mode is to use the same at each end of a link (use a constant). Idle low saves a bit of power. Have you got anything on the serial in download pin. Make sure it is pulled down. A 5/8 aerial may be better than a 1/4 wave. You might consider a check sum. Add all the tx bytes (ignore overflow) and send the result as an additional byte. Check at the rx that the sum works.

I'm lucky enough to have a spectrum analyser (ebay) and I can see four or five similar signals on or about my signal, even though I live out of town. So I don't get a perfect throughput.
 

manuka

Senior Member
I seem to have spent half of the last decade helping folks with 433 MHz data devices, & IMHO the golden rule is to "Start VERY simply !". Aside from a Forum search,perhaps check insights given at my PICAXE resource site
 

Dippy

Moderator
Alastair, I assume this is your first dabble with RF. I'm never sure whether using super-cheapo stuff alone is a wise first move, but in any event, do as Stan (Manuka) advocates and start simple.

At the moment you don't know if the Trasnmitter is transmitting or if the receiver is actually receiving.
You don't know if your data is getting to the Tx or if anything is popping out of the Rx.

Have you only bought 1 x Tx and 1 x Rx?
If so, bad move.

Can you 'scope the output of the RF receiver to see if something is coming through?
If it is then just transmit a couple of bytes and use the trigger to view the received signal.
Then you can check.

Or use a piezo just to see if SOMETHING is coming out.

The problem is that you have got two super-cheapo devices which will not be factory tested.
And you don't know what's happening as you don't have any test equipment.

Wasn't it this same make/supplier that someone else used recently and they'd sent the wrong receiver?
That sort of thing always inspires me with confidence.

You have to start removing variables.
Run it all at 5V or 3xAA for a start so there aren't any possible level problems.
Have you read/understood/tried the KLP Walkthrough??


Stan, I reckon it's time for you to write a nice Tutorial.
They were the 'fashion' last week.;)
I'm sure all the info is on that link, but I'm afraid those insights are a little difficult to read and digest.
It's all a bit squashed up and brief.
Some nice spacing is required to make it more readable. Put it on a sheet or two of A4 in Arial font and that would be really useful.
:)
 

NXTreme

Senior Member
Ok, I moved over to Windows to upload the code. It seems to have disappeared :(. I'll see if I can remember what it did...

TX:
Code:
Read potentiometer connected to ADC pin.
Transmit value using serout with qualifier (U) before it.
Wait 5 ms.
Repeat.
RX:
Code:
Wait for qualifier (U).
Read analog value into variable.
Blink LED based on value. Example: analog value=106. Pin x high for 106 ms, then off for 106 ms.
Repeat.
Now, there is a bug there. The transmitting Picaxe is always transmitting and the receiving Picaxe won't catch all the packages. However, this keeps the receiver tuned so you don't lose many packages till your out of range. If this concept works the same way my code did the LED will "lock up" if it starts receiving bad packages. This helps with determining what percentage of packets your receiving.

Keep in mind that this concept could be greatly improved. Also, I used the SparkFun 4800 baud receiver as it seems to "lock onto" the signal better.
 

alistairsam

Senior Member
No, I used three AAs for the transmitter and a 9V battery regulated down to 5v for the receiver. I'm dual-booting, otherwise I'd give you the code (it's on the Windows partition, I'm on Linux right now). Next time I boot up Windows I'll post the code. I used two 08Ms and I suggest you do too if you want to keep it simple. Get it working simply at first, get more advanced later. I do suggest the 315Mhz modules just because you will most likely have less interference using them instead of the 433Mhz variety.
thanks. so you connect the battery terminals to the transmitter, and use a separate battery and 5v regulator to the picaxe?
I was wondering if I can use a single 9v battery direct to the transmitter, but connect it also to the 5v regulator and run the picaxe?

hippy, I tried the T{baud rate} instead of the N, but has not made any difference. hardly any data getting through.
 

alistairsam

Senior Member
Alastair, I assume this is your first dabble with RF. I'm never sure whether using super-cheapo stuff alone is a wise first move, but in any event, do as Stan (Manuka) advocates and start simple.

At the moment you don't know if the Trasnmitter is transmitting or if the receiver is actually receiving.
You don't know if your data is getting to the Tx or if anything is popping out of the Rx.

Have you only bought 1 x Tx and 1 x Rx?
If so, bad move.

Can you 'scope the output of the RF receiver to see if something is coming through?
If it is then just transmit a couple of bytes and use the trigger to view the received signal.
Then you can check.

Or use a piezo just to see if SOMETHING is coming out.

The problem is that you have got two super-cheapo devices which will not be factory tested.
And you don't know what's happening as you don't have any test equipment.

Wasn't it this same make/supplier that someone else used recently and they'd sent the wrong receiver?
That sort of thing always inspires me with confidence.

You have to start removing variables.
Run it all at 5V or 3xAA for a start so there aren't any possible level problems.
Have you read/understood/tried the KLP Walkthrough??


:)
Hi
yes, this is my first dabble with RF and I did a fair bit of reading of the threads here and thought i'd experiment with the 434Mhz modules first.

I am heeding manuka's advice and starting simple. I'm just sending some numbers and seeing if the receiver received it.
what I did was to transmit a single number from the transmitter, and at the receiver, displaying it if it value from serin is that number, and clearing display if its not.
that has helped quite a bit as I got an idea of the range and how often the data does gets through, which is not that often unfortunately.

what I also did was to keep the receiver and LCD on and the transmitter off.
no qualifier at the receiver and transmitter.
that way all interference would show up as numbers. then when I turn the transmitter on, I monitor what happens to the numbers.
what I found that there is a lot more data with the transmitter on than when its off. so I know my transmitter is working, and I was able to view a simple counter transmit on the LCD when I positioned myself between the two. so I do know the transmitter is working.

just need to get the qualifier, preamble, antenna, tx power correct. will also try the 315 mhz modules.

I did use a scope at the receiver and was seeing patterns of signals coming through.
 

lbenson

Senior Member
If you remove the transmitter and receiver and replace them with a wire (plus another wire connecting the grounds of the two circuits) do you receive exactly what you send? This is a good way of testing that your code on both ends is right before you move on to the hardware of TX and RX.
 

NXTreme

Senior Member
thanks. so you connect the battery terminals to the transmitter, and use a separate battery and 5v regulator to the picaxe?
I was wondering if I can use a single 9v battery direct to the transmitter, but connect it also to the 5v regulator and run the picaxe?
I actually connected the same 9V battery to both the transmitter and the 5V regulator. It worked too! I'd also include a capacitor (10-100uF) across the Picaxe's power leads so that you don't have problems with noise. Not necessary, but it lessens the chance of problems.
 

alistairsam

Senior Member
I actually connected the same 9V battery to both the transmitter and the 5V regulator. It worked too! I'd also include a capacitor (10-100uF) across the Picaxe's power leads so that you don't have problems with noise. Not necessary, but it lessens the chance of problems.
ok. will try the 9v battery to the transmitter, will also place a 2k2 resistor in series to the picaxe output just in case.
you'd want to connect a 0.1mfd decoupling cap in parallel to the picaxe supply. the 100mfd may not help as its usually for filtering or smoothing out ripples, but since your supply is from a battery, there won't be ripples. but no harm in placing it.
 

MFB

Senior Member
I posted this comment some months ago but think it may still be pertinent...

"I can’t help coming to the conclusion that getting a basic rf link to work by trying to balance bits is like training a dog to walk on it’s hind legs. Although the result is not very elegant, it is amazing the dog can manage it at all.

Unless we want this topic to keep appearing on the forum, it may be time to come up with a more reliable alternative (e.g. code for Manchester or FSK encoding)".
 

Technical

Technical Support
Staff member
Unless we want this topic to keep appearing on the forum, it may be time to come up with a more reliable alternative (e.g. code for Manchester or FSK encoding)".
The AXE213 RF connect kit is now available for resolving exactly this kind of issue -it does come up very often! The datasheet is not quite complete (www.rev-ed.co.uk/docs/axe213.pdf) but the kit is available from today (www.techsupplies.co.uk/AXE213). AXE213 will be formally announced when the datasheet is finished but a sneak peek is available now for those interested!
 

MFB

Senior Member
Well Done!!!

Technical, that’s a very impressive response to the rf communications problems often described on this forum.
 

eclectic

Moderator
I'm impressed! N.B- their NKM2401 encoder/decoder chip needs a steady 5V.
As a relative novice,,
I'm confused now. :-(

From the AXE213 Datasheet, page 32

NKM2401 Technical Specifications
Ambient Temperature 20° C
Supply Voltage +5.0 V
Parameter Min Typ. Max Units Notes
Supply Voltage 3.0 5.0 5.5 Volts


I was hoping to use 3 x AA NiMh or Alkaline.

e
 

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hippy

Technical Support
Staff member
Before too much confusion on the voltage requirement sets in, my take on it is ...

The NKM2401 is implemented on a PICmicro so operates on whatever to 5.5V ( I cannot recall exactly what the whatever is off-hand ). As with many PICmicro the defacto operating voltage is 5V. Nikam Electronics state a fairly tight range of operating voltage in their specification. Our AXE213 datasheet states a wider range at which our chip will operate within specification.

The RF Modules themselves though may require closer to 5V to operate, going too far above may damage them, and going lower may cause a reduction in performance and range. You need to consult the module datasheets.

I've used the AXE213 transmitter with 5V, 4.5V ( 3 x AA batteries ), and also at 3V and they do work. How acceptable at below 5V will depend on RF modules chosen and performance desired.
 

alistairsam

Senior Member
I posted this comment some months ago but think it may still be pertinent...

"I can’t help coming to the conclusion that getting a basic rf link to work by trying to balance bits is like training a dog to walk on it’s hind legs. Although the result is not very elegant, it is amazing the dog can manage it at all.

Unless we want this topic to keep appearing on the forum, it may be time to come up with a more reliable alternative (e.g. code for Manchester or FSK encoding)".
you're right, but I have seen some code in this forum for Manchester encoding.
my issue is I'm not able to get the receiver to lock on to my transmission even with the preamble and pause.
i tried hooking up 9v to the transmitter instead of 5, but did'nt help.
one thing I did not do is solder wires to the common connectors at both ends of the receiver. it has pins on both sides which are common and are internally connected, so I did not connect both sides externally. just one side.
 

manuka

Senior Member
Hippy: Thanks for the confirmation. I'd half suspected they were a tweaked PIC from their supply pins,and that data sheet looks a tad too user friendly as well. They may just be an regular rebadged PIC12F683 in "poor man's" ASIC (Application Specific IC) disguise,meaning supply voltages indeed can be more flexible.

Alistairsim: Mate- don't put yourself thru' this pain! Pop into the nearest Jaycar & buy/borrow a 433 MHz pair (ZW3100 & ZW3102), and wire them up SIMPLY !!!! They're not the most sensitive or powerful (nor cheapest), BUT they're super reliable & always work. I STRONGLY advise 433 MHz band monitoring also, as your site may suffer heavy local interference. Stan.
 

alistairsam

Senior Member
Hippy: Thanks for the confirmation. I'd half suspected they were a tweaked PIC from their supply pins,and that data sheet looks a tad too user friendly as well. They may just be an regular rebadged PIC12F683 in "poor man's" ASIC (Application Specific IC) disguise,meaning supply voltages indeed can be more flexible.

Alistairsim: Mate- don't put yourself thru' this pain! Pop into the nearest Jaycar & buy/borrow a 433 MHz pair (ZW3100 & ZW3102), and wire them up SIMPLY !!!! They're not the most sensitive or powerful (nor cheapest), BUT they're super reliable & always work. I STRONGLY advise 433 MHz band monitoring also, as your site may suffer heavy local interference. Stan.
Stan, thanks for the advice. i might just do that. but before i do, can someone please recommend what would be ideal for my application, transceivers, or independent transmitter receivers, AM, FM or other

i need to have a handheld device that transmits 5 button states to a picaxe, and also receive a continuous stream of data of 6 variables from another picaxe next to the first one to display on its LCD, and send two button states to a third picaxe.
this is for telescope control so range is only a few feet, but what is needed is reliable comms.

following is what I found as wireless transceivers or rx/tx.

I came across the ASK modules like the ones i'm attempting to use at 433Mhz, 315Mhz, and 915Mhz, nRF24L01+ 2.4Ghz transceivers (no idea how to interface to a picaxe), the hobby radio controls and receivers from pololu, the ISM band FSK transceiver module RFM12B-S2, and the Transceiver nRF2401A with Chip Antenna.
would you'll be able to suggest what I should go for that would have reliable comms, and can tolerate one more transceivers next to each other and can be used with picaxes.
 

Dippy

Moderator
Questions:

1. A couple of feet? Why not IR? (edit, I just noticed your continuous stream. IR may be dicky).
2. With tiny ranges you may totally splat the the receiver with RF i.e. (overload).
3. Your experience (so far) isn't enough to develop a system with those tiny RF chips. You could make something amazing with a CC1101 but it's technically a little tricky.
4. Budget?

Some people may suggest XBee. They'd be reliable but a little pricey. AND they can't handle a continuous stream, you'd have to packetise and pause.
There may be some device around which are good. I'd be a little picky and look for ones that can adjust the output RF power or are low power spec out of the box.


ALWAYS practice your serial comms bit with wire before moving to RF.
An RF link should be very easy. With a 'scope and multimeter you should be able to get something going in an hour - otherwise you are doing something fundamentally wrong. Sadly, (or maybe fortunately!) we can't see over your shoulder.

AND a nice picture (DRAWING) would make your system requirements so much easier for everyone else to understand - it would take you as much as 10 minutes and save hours of potential unclear replies.
Join the AAL - the Anti Ambiguity League ;)
 

hippy

Technical Support
Staff member
would you'll be able to suggest what I should go for that would have reliable comms
Any simple 433MHz system should get reliable comms if you have set it up right. I still suspect it's simply that you are using wrong serial polarity but the total number of things involved can still make it a pain to get working. That's why we have introduced the AXE213 so you don't have to worry about complicated serial protocols and timing.

and can tolerate one more transceivers next to each other and can be used with picaxes.
A multi-node wireless system is a big step up from a single one-way wireless link we have been discussing so far and will involve things like arbitration and collision detection. For that it's best to use modules which can handle all that for you such as XBee.
 
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alistairsam

Senior Member
Hi

I will draw a schematic of what I'm trying to do shortly.
I started with IR, but issue is sometimes, the scope can be inbetween the base and the handheld.

as for a continous stream, I had some success with the 433 Mhz modules that I got from sparkfun in that i had a simple counter from 0 to 240 and got that to display on the receivers LCD when i was :) at an angle between the two. I know it sounds strange, but I saw the numbers incrementing linearly quite a few times.
so brief pauses of upto 150ms should be fine as the encoder data and position info is held in the base station picaxes.
the schematic will make it a bit more clear.

I might give the modules from Jaycar a shot, and get a 433Mhz pair and 315Mhz pair and test. reading from all the posts here, if the pairs are matched and tuned properly, they should work, especially with the preamble and pause that so many have tested here.
its possible that my pair is not matched properly, hence my unreliable comms.

Electronics wise, i should know about RF, as I'm an electronics Engg, but have'nt been in the field for a while, more into computer networks, so bit out of touch, but am more than handy with SMD's, components, scopes etc.
am learning the theory behind bits, bytes, picaxes and RF and how you'll manipulate bits for manchester encoding or CRC.

I was thinking of the xbee's as well. have to work out to see what it'd cost. i can go upto $200, but that'd be it.

as mentioned, will post the schematic.
 

Technical

Technical Support
Staff member
Hippy: Thanks for the confirmation. I'd half suspected they were a tweaked PIC from their supply pins,and that data sheet looks a tad too user friendly as well. They may just be an regular rebadged PIC12F683 in "poor man's" ASIC (Application Specific IC) disguise,meaning supply voltages indeed can be more flexible.
See here for more details www.techsupplies.co.uk/NKM2401
 

manuka

Senior Member
Just a few feet ! ASK would be quite OK,with RF overload no doubt the main concern.

IR seems near overwhelmingly your friend here, especially since it's so simple now to generate & decode with a 08M. You could even use a coin shop TV remote as the controller,and spend most of the $200 on something sensible - like rum to keep you warm on chilly nights.

PICAXE IR control is usually good enough for 10s of metres in the dark LOS, & it won't do in your night vision! If things are in the way visually perhaps just bounce the IR off the roof or some handy reflective surface (perhaps not the moon however). Stan.
 

techElder

Well-known member
Except for the educational value, it's just nuts to use RF or IR for "a few feet."

Get some wire and be ultimately reliable! :confused:
 

alistairsam

Senior Member
Any simple 433MHz system should get reliable comms if you have set it up right. I still suspect it's simply that you are using wrong serial polarity but the total number of things involved can still make it a pain to get working. That's why we have introduced the AXE213 so you don't have to worry about complicated serial protocols and timing.
Hippy, when will the AXE213 be available, I presume through Microzed for folks in Australia. is the NKN chip available separately?
I tried both N and T polarity and made sure both sides were matched, but it made no difference. some data got through, most of it did not.
 

alistairsam

Senior Member
Schematic of what my current setup is. (With wires).
trust me, they really can be messy and dangerous in the dark when in dark sky sites where its pitch black, and can easily get entangled when the scope moves, especially since one wire goes to one end of the scope, another two goes to another end.
hence my need for wireless.

I know IR sounds sensible, but issue is that I'd have to point or atleast be pointing roughly in the direction of the receiver. the Vishay IR detectors do have quite a large receiving angle, but when I'm on the other side of the scope, pointing is quite difficult, especially with one eye in the eyepiece.

had a look at the xbee's, they sound more practical for my application as they support multipoint as hippy mentioned. they're around $30 each i think.
 

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Dippy

Moderator
"I know IR sounds sensible, but issue is that I'd have to point or atleast be pointing roughly in the direction of the receiver"

- yes, that's why I did my edit. I left my original in there so other people could see (and ignore) the use of IR.

I'm not sure if AXE213 is applicable, sizewise.
Can you adjust power for really short range?
And am I right in saying that a made-up 'transceiver' pair would cost £40 ?
(I'm sure they'll make life easier for many who wish to do a simple link - so don't think I'm being negative. I don't want to incur the wrath!)
 

alistairsam

Senior Member
"
- yes, that's why I did my edit. I left my original in there so other people could see (and ignore) the use of IR.
i saw your edit but mentioned IR just to explain why it may not be practical.

using naming convention from my schematic, I had the initial idea to use a 315Mhz transceiver for the LCD data and unit A.
And as the other two units need just button inputs, I thought I could use two 434Mhz receivers, one for unit B and one for unit C, and one transmitter for the handheld remote. I could then use addressing in my transmission when buttons are pressed, so the respective unit responds or drives the motor.

the LCD and unit A will need transceivers as there will be a few button inputs from the handheld to unit A, this is for calibration of the encoder position.

if I just use all the transmitters and receivers without any antenna, and I use 315Mhz and 434 Mhz for the different modules would there still be too much interference?

I saw the video of the picaxe controlled window blinds in this forum and noticed he had a transmitter and receiver next to each other on the same PCB. but not sure if he was using TDM to switch between the two.
 
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