B
Ben Hitchcock
- Jan 1, 1970
- 0
Hi,
This message is being posted in the hope that if someone else runs
into the same problem as I did then they'll find this post via Google
groups and not bang their head against the wall!
So I'm not after an answer. Ignore if you like.
The story: I bought a couple of transceiver units from Oatley
Electronics (http://www.oatleyelectronics.com/remote.html part
TRX433). I made a veroboard support board for this, with a handful of
components (5V regulator, LED and a couple of wires). No matter how I
tried, I couldn't get those darn things to communicate! I tried
connecting wires to the +5V and 0V rails and transmitting this signal,
but it seemed as if the receiver had a mind of its own. It looked
like the two were communicating, but the sense of the output signal
wasn't really as good as I'd hoped. I'd brush the TxD line against
the +5V rail, and the output line would flicker then be either high or
low, depending on some random factor.
I then set them up with a 555 timer set up as a 1Hz oscillator on the
TxD data pin. With the other one I put a LED on the output pin,
connected through a 1k resistor.
With everything turned on, only the first 'spike' of the 1 Hz got
through, the rest of the time the LED is off. So the transmitter has
a 50% duty cycle, whereas the receiver shows only about a 2% duty
cycle. It does appear as if the two units are in contact with each
other, however. Turning the transmitter off makes the receiver flash
the LED erratically, which is to be expected with the random RF
bouncing around my neck of the woods.
Swapping the modules so that the other one is the transmitter, and
vice versa has no effect -- the modules still behave the same way.
After much frustration and mucking around with ground planes,
decoupling caps, etc, I realised that you need a big voltage swing for
this module. You need a full rail-to-rail voltage swing on the
transmitter Txd line for it to work reliably, and I do mean full
rail-to-rail.
Hopefully this information helps someone in the future. Now if only I
can figure out how to make a decent aerial!
Ben
This message is being posted in the hope that if someone else runs
into the same problem as I did then they'll find this post via Google
groups and not bang their head against the wall!
So I'm not after an answer. Ignore if you like.
The story: I bought a couple of transceiver units from Oatley
Electronics (http://www.oatleyelectronics.com/remote.html part
TRX433). I made a veroboard support board for this, with a handful of
components (5V regulator, LED and a couple of wires). No matter how I
tried, I couldn't get those darn things to communicate! I tried
connecting wires to the +5V and 0V rails and transmitting this signal,
but it seemed as if the receiver had a mind of its own. It looked
like the two were communicating, but the sense of the output signal
wasn't really as good as I'd hoped. I'd brush the TxD line against
the +5V rail, and the output line would flicker then be either high or
low, depending on some random factor.
I then set them up with a 555 timer set up as a 1Hz oscillator on the
TxD data pin. With the other one I put a LED on the output pin,
connected through a 1k resistor.
With everything turned on, only the first 'spike' of the 1 Hz got
through, the rest of the time the LED is off. So the transmitter has
a 50% duty cycle, whereas the receiver shows only about a 2% duty
cycle. It does appear as if the two units are in contact with each
other, however. Turning the transmitter off makes the receiver flash
the LED erratically, which is to be expected with the random RF
bouncing around my neck of the woods.
Swapping the modules so that the other one is the transmitter, and
vice versa has no effect -- the modules still behave the same way.
After much frustration and mucking around with ground planes,
decoupling caps, etc, I realised that you need a big voltage swing for
this module. You need a full rail-to-rail voltage swing on the
transmitter Txd line for it to work reliably, and I do mean full
rail-to-rail.
Hopefully this information helps someone in the future. Now if only I
can figure out how to make a decent aerial!
Ben
