IR Sensors

[simrat.s]

How many IR sensors can are you allowed to have on the 2008 Robot?

In the rules (<R65>) it states:
"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."

[RyanN]

By the rules, you can have as many IR Receiver boards as you want, as long as you do not use more than 4 commands total, so there is no reason to have more than one since you cannot use more than one.

[fimmel]

you could have one on each end of the bot (front and back) so the robocoach will always be able to signal

...forest

[lukevanoort]

Originally Posted by fimmel

you could have one on each end of the bot (front and back) so the robocoach will always be able to signal

...forest

There are other solutions too that might, hypothetically, involve gyro, encoders, and servos....I really like StangPS

[ccsingle07]

If you can have as many IR sensors as you want. Does that mean you can have as many Remotes as you want. As long as there are 4 signals of course.

[neutrino15]

I actually would like to know if you could combing the output PWMs from 2 IR recievers (for front and back) in such a way that it does not violate first restrictions.. I mean, if a digital signal is just +5v to 0, why couldn't you just combine the digital pins? This way you don't have to burn 8 inputs..

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[tlawless]

Two things.

1. I believe the output from the IR board is simply a digital signal, not a PWM output (if you're unsure of the difference let me know, I'd be happy to explain!).

2. I don't think you'd be violating any rules by joining the digital inputs from two (or more) IR receivers. Just keep in mind that your digital pin would be exerted when either of the two boards receives the signal. This essentially doubles your chances for signal interference. Also keep in mind that you can use an analog input for a digital signal, just not the other way around.

[Schooj]

As far as multiple boards for reception go, they are not necessary. I did extensive experimenting with these when they came out a few years ago and discovered that despite the "window" in the front, the whole sensor case is fairly transparent to IR. This may have changed though since that was one of the main problems of the original IR sensor.

[Ziaholic]

Originally Posted by neutrino15

I actually would like to know if you could combing the output PWMs from 2 IR recievers (for front and back) in such a way that it does not violate first restrictions.. I mean, if a digital signal is just +5v to 0, why couldn't you just combine the digital pins? This way you don't have to burn 8 inputs..

--

It is normally not a good electrical practice to directly wire 2 outputs together ... as one of them can drive a signal into the other. It can be especially damaging if the INPUT that they are connected to has a high impedance.

I haven't looked at these circuits specificially, but typically outputs don't like to get external excitation. It all depends on the type of output circuits ... and whether or not you add external circuitry to isolate/protect the drivers.

Will it work? Maybe. Will if fry the board? Maybe, maybe not. I'd have to look at the driver circuits to see if they have protective circuitry.

[dcbrown]

It is normally not a good electrical practice to directly wire 2 outputs together ... as one of them can drive a signal into the other. It can be especially damaging if the INPUT that they are connected to has a high impedance.

You can look at a techniquie called wire OR'ing. You wire two or more outputs together, but not directly as you indicated. It can be done with steering diodes, for example: tie all four outputs together through a wire OR into a single interrupt (port B pin). Each pin could also be directly tied to a generic digital input pin. Interrupt fires, then interrupt code reads the generic inputs. The purpose would to tie up only 1 interrupt pin.

[Al Skierkiewicz]

The First documentation says this device is an implementation of the aTinyIR2 device. The schematic for the TinyIR2 shows a PIC controller and implies that the outputs come from some tri-state pins on the controller. As such there is no way to know whether it is safe to "OR" the outputs of several boards together with simple wiring. It might be OK to use diodes but I am not sure it is worth the frustration of trying to troubleshoot two boards and get them working together.

http://www.tauntek.com/TinyIR2-schematic.pdf

[popo308]

Originally Posted by ccsingle07

If you can have as many IR sensors as you want. Does that mean you can have as many Remotes as you want. As long as there are 4 signals of course.

The manual clearly states 1 remote per team.

[tlawless]

Out of curiosity, where does it state that you are only allowed 1 IR board? I ran a few searches through the manual and found nothing.

[Alan Anderson]

Originally Posted by tlawless

Out of curiosity, where does it state that you are only allowed 1 IR board? I ran a few searches through the manual and found nothing.

I think the fact that the board is only available in the Kit of Parts, and only one of them is provided, clearly indicates that only one may be used.

This could change if the board became available for purchase as an off-the-shelf item.

[tlawless]

If you're not able to find additional boards thre's nothing stopping you from building a similar device. I haven't found anything in the rules that states that you can't use more than 1 of the supplied boards though, regardless of how difficult they may be to find.