I am planning to build a robot that uses a Sharp GP2D120 for IR object
I would also like to control it using a VCR remote control and the Sony
Is there any way of doing this without the IR signal from the remote
control causing the GP2D120 to think it's detected an object?
Any feedback will be appreciated.
Decode all the characters on the Sony remote. Find a unique character that's
not on the remote. Transmit the unique character from your IR LED (used to
detect objects)with some time between the character being sent and when
receiving and decoding characters use that character as an object detected
condition. You will still need to deal with receiving the remote and
detecting the object at the same time but this will allow the receiver to
identify the signal being detected as an object or a command.
Hope this helps,
It sounds like the distance detector is a canned solution that you
can't change, which may limit your ability to solve problems.
One thing you could do is simply sanity filter the output - if the
distance reading jumps, take another. Don't believe anything that
doesn't read the same (+/- error) twice. Harder if you have it
spinning to scan the room...
If you were designing both IR systems from scratch, using different
modulation frequencies would help. It's possible they are already
different - have you tried and verified a problem? When the IR
transmitter and receiver are adjacent, it's easy to use synchronous
detection (turn on the source, read, turn off the source, read,
subtract) to get noise immunity - the module may already do that. When
the source is something else, you are limited to filtering based on
frequency (or much more complicated, pseudorandom code) and checking
the data for validity with a checksum, etc.
Would polarizing filters work with IR?
Have you tested to verify there's actuall a problem?
You should be able to shield the GP2D120 from the IR remote control,
although reflection could be a problem. I wonder if the hood could
be made from something that wouldn't reflect IR? However, I'm also
guessing they are modulated on different frequencies, so you might be
trying to solve a problem that does not exist.
If you simply can't make this happen, for whatever reason, try the
TLP434/RLP434 Easylink Wireless modules. They use RF at 434MHz. They
should work reliably, although they will cost more and take more power.
I missed the OP's post, so I'll respond to this one.
Most of the Sharp distance sensors have a very slow modulation compared
to the typical 38-40K modulation of an infrared remote. The differences
in modulations should never cause the output of the distance sensor to
false-trigger the IR remote input.
However, the output of the distance sensors, while a very narrow beam,
is quite bright, so it could conceivably swamp the IR receiver. Merely
mounting the two to avoid this problem should not be hard. The distance
sensor uses a PSD device that would require you to point the IR remote
directly into the aperture of the sensor, in order for any interference
to occur this way. The Sharp distance sensors are made for varied light
environments -- such as brightly lit public restrooms -- so a baffle or
shield shouldn't be necessary.
This shouldn't cause much of a problem -- The Sharp detectors use a
modulated signal of ab0ut 1 khz with a 10% duty cycle. The remote
control detector/demodulators use a signal of around 38-42 khz. In
general, this won't cause a problem -- one of my robots uses the sharp
detectors as auxiliary obstacle detectors and can also be controlled via
VCR remotes -- I've not noticed any issues in practice.
Hope that helps -- tAfkaks