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Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
I am trying to create a link from outside the house to inside the house, i am using a visual basic program on the computers end, and i am having enormous trouble using these 'wireless modules' which can be found on a) unreliable to get a signal from that distance/position b) even when i occasionally do there is so many errors, i dont know how to deal with it (i have tried multiple things)
Does anyone know of a hassle free easy way to do this using cheap and easy to obtain parts in Australia? my computer has a serial port, bluetooth, and wifi, if that helps.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Your link doesn't go directly to the modules you speak of, so its somewhat difficult to determine exactly what would help, but here are some starting points.
Antenna: A hunk of wire will work, but not well. You need to know the feed point impedance first off. If these are the 433MHz modules I think they are, it will be a 50 ohm unbalanced feedpoint impedance.
A 433MHz 4 or 5 element Yagi or Cubical Quad directional antenna would be trivial to construct, and one on each end could increase your effective signal strength by nearly an order of magnitude. There are myriad websites that describe various antenna designs for ham radio, and 433MHz just happens to fall in the 70cm ham band. A 5 element cubical quad would fit inside a shoe box and cost less than $5 to build it you didn't already have everything.
Elevation: Get the antenna on both ends up. As high as is practical, or at the very least try to find an unobstructed path. 433MHz is susceptible to scattering from foliage, buildings, heavy precipitation, etc.
High error rates can be caused by a number of things. Signal distortion (a transmitter/receiver problem), signal fade (antennas will fix that), direct interference from other radiators, or indirect interference in the form of receiver desensitization due to a nearby powerful transmitter on a harmonic frequency. To say those modules lack filtering is an understatement. Decreasing the data rate or adding parity can help, but only so much.
Give us some details, I'm sure we can help you get something working. If I can bounce a 430MHz signal off the moon with a $200 radio and be heard on the other side of the earth, we can get your signal a few hundred yards :)
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
1st thing to help solve the problem would be to know what you are making
remote generator monitor
Also If you would link ur Schematic It help help also
attached and if you want to know why i have a comparator in there, well the output current is not high enough to drive the cmos/ttl input input of the max232 chip
Antenna: A hunk of wire will work, but not well. You need to know the feed point impedance first off. If these are the 433MHz modules I think they are, it will be a 50 ohm unbalanced feedpoint impedance.
is a '315/433.92Mhz Hybrid' transmitter datasheet: reciever datasheet: are they even meant to work together? the transmitter says ASK and the reciever says on-off keyed yeh it says 50 ohm, im using a breadboard, does that factor into it? (Xc)
A 433MHz 4 or 5 element Yagi or Cubical Quad directional antenna
oh, i guess ill have to look up about those, no idea really since its hybrid what frequency should i even use?
Elevation: Get the antenna on both ends up. As high as is practical, or at the very least try to find an unobstructed path. 433MHz is susceptible to scattering from foliage, buildings, heavy precipitation, etc.
this is just about impossible due to the location i need to put it in (about the plants), only thing i could do is stand it on something to lift it up a bit
High error rates can be caused by a number of things. Signal distortion (a transmitter/receiver problem), signal fade (antennas will fix that), direct interference from other radiators, or indirect interference in the form of receiver desensitization due to a nearby powerful transmitter on a harmonic frequency. To say those modules lack filtering is an understatement. Decreasing the data rate or adding parity can help, but only so much.
It works if i have them together in the same room, so im mostly sure the circuit is ok. Im running them at 1200 baud
Give us some details, I'm sure we can help you get something working. If I can bounce a 430MHz signal off the moon with a $200 radio and be heard on the other side of the earth, we can get your signal a few hundred yards :)
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
The transmitting frequency depends on the crystal. Find the crystal frequency and multiply with 64 and you will probably get the transmitting frequency. The chips themselves often work at a range of 300-1000 MHz. The modules are fitted with different crystals depending on what they are used for and where they are supposed to be sold.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
If you are trying to send data (ie: serial), an xbee module might be the way to go since it is designed for data, has error checking/correction and is a rx/tx pair (remote control generator anyone?) The basic version only goes 100m, the more expensive version can go supposedly up to a mile.
Also, isn't your 3.3v regulator missing smoothing caps on the input/output and more importantly a stepdown transformer? The 7833 won't handle 120vdc input, but a small transformer (even a bell transformer from home depot) could step it down to 12v which is reasonable with a small heatsink.
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
The transmitter does not have a crystal, the reciever crystal only has the text "V6772CAH004" on it. 120v?!?!?! try 6v! clearly some logic would indicate i am not attempting to recharge a 6v battery with 120v!
yeh, ive heard about these xbee modules, though have not found one yet at an actual store. and would probably still need to build an antenna anyway?
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Avi wrote ...
The transmitter does not have a crystal, the reciever crystal only has the text "V6772CAH004" on it. 120v?!?!?! try 6v! clearly some logic would indicate i am not attempting to recharge a 6v battery with 120v!
yeh, ive heard about these xbee modules, though have not found one yet at an actual store. and would probably still need to build an antenna anyway?
The xbee modules are almost *always* ordered in from the internet. The modules can either be ordered with built in antenna, or (I believe, not 100% sure, check datasheets) with a SMA connector (more useful for the pro with directional cantenna or any wifi antenna since its 2.4ghz already)
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wireless link between microcontroller and computer
