Custom IR Board

[robbrad]

I have tried to build an IR remote from scratch befoe and had problems distinguishing a signal from ambient light. Does anybody have an idea on how the learning recievers take care of this? I would very much like to create a custom IR reciever board to take care of possible compatibility issues. If we are required to use common IR Com protocals for the device to recognise the data packets, I see a compatibility issue, especially if teams like to use the arrow keys on their remotes. I would like to design a board that uses a start byte, our team number, to rule out any possible "command overlap." Any filtering advice would be greatly appreciated. Thanks.

[Larry R]

To use a TV remote you need a special IR receiver that will recognize the 38.5 KHz modulation. The output of that IR receiver will be the pulse train that you send out from the TV remote control or equivalent device you build. They are easy to find - Parallax sells such a receiver at low cost. Connections are simple with three pins: +5v, ground and pulse out.

The FIRST IR board uses such a receiver.

Note: the special receiver is much different that the analog approach using an IR LED and an IR sensitive photo detector.

Cheers, Larry

[mneary]

If we are required to use common IR Com protocals for the device to recognise the data packets, I see a compatibility issue, especiallyCheck the rules again! I only have a moment, so I can't look it up for you. You can use IR, visible light, or sound (almost anything except lasers or Radio Frequency). No mention of protocol is made, the IR board is apparently supplied as a working example.

Anything I say isn't official, I'm hopefully pointing you to re-check your rules.

[edit: I looked up <R65> and attached it below.]
<R65> SIGNALING DEVICES shall be designed to communicate signals from the ROBOCOACH
to the ROBOT. SIGNALING DEVICES are excluded from Rule <R64>. SIGNALING
DEVICES shall:
 use either passive (no emission of any electromagnetic radiation) or active (emits some
restricted form of electromagnetic radiation) means of communication
© FIRST2008 FIRST Robotics Competition Manual, Section 8 – The Robot, Rev C Page 23 of 30
 be hand held and completely supported by the ROBOCOACH when operated
 does not attach to anything or anyone other than the ROBOCOACH
 exclusively receives input from, and is operated by, the ROBOCOACH
 not receive any input or feedback directly from the ROBOT (the ROBOCOACH may
receive feedback from the ROBOT and use it to control the SIGNALING DEVICE)
 be no larger than 3 feet tall by 3 feet wide by 1 foot deep (to fit within the confined
volume of the ROBOCOACH STATION
 remain entirely within the ROBOCOACH STATION
 use a maximum of four different inputs from the ROBOCOACH (e.g. use four different
buttons) during any single MATCH
 communicate no more than four messages, states or conditions to the ROBOT (please
refer to Rule <R69> and Rule <G01> for additional information) during any single
MATCH.
Active SIGNALING DEVICES shall:
 use visible light, infrared communications, or sound as the transmission method – no
other form of electro-magnetic radiation is permitted
a. All radio frequency communications (as defined by the United States Federal
Communications Commission) are explicitly prohibited.
b. All laser-based communications by any device classified by the U.S.
Department of Labor Occupational Safety and Health Administration (OSHA)
as a laser are explicitly prohibited.
c. All communications must satisfy Rule <S01>.
 not be used to interfere with any other ROBOT
 be able to switch between no more than four states or conditions (i.e. send no more than
four messages)
 be operated through only a single input at any given time (e.g. may not be operated by
depressing two buttons at one time)
 not use changes in the signal states to encode or transmit larger messages (e.g. Morse
code)

[robbrad]

By "required to use common protocals" I ment that the IR board we recieved in the kit will only recognise certain protocals, a protocal we have to transmit if we expect it to work. If we use IR, I would build my own remote and reciever and create my own protocal, start byte (team #) and data packet. As long as there are only 4 commands, I don't see a rule violation. Am I overlooking something? How do I filter out ambient light to recognise a data packet?