Fun with sensors

[Team852]

Hi, I was wondering if anyone knew where the explanation is of how to connect the sensors to the robot controller. If you know where that documentation is, or you can tell me that would be greatly appreciated.

Thank you,
Daniel (Team 852)

[rbayer]

All documentation for the control system is here:

http://www.innovationfirst.com/FIRST...umentation.htm

You want to the "Full-Size Robot Controller Reference Guide" for wiring, etc.

[Team852]

Yeah, tahkn you, but does it also explain how to plug in the ir sensors into the rc. Because there are 4 wires, and for normal analouge sensors, you only need two. Will it explain certain things like ir sensors, or will it even tell you the way to plug in a 4 wire sensor.
Thanks again,
Daniel (852)

[FotoPlasma]

The pinout is on the side of the sensor.

http://www.chiefdelphi.com/forums/sh...tical+ sensor

[rbayer]

Ah, I see your problem. Only three of the wires are actually used, but you have to decide which three. Here's a quick run-down of all four wires:

Brown --> +12V (from main electrical system)
Blue --> Ground on RC switch inputs
Black --> Switch input
White --> Switch input

Now, you're probably wondering why both Black and White go to sensor input, and justly so. Pick one or the other, and only use that one. But be consistent--if you decide to use the white wire, use the white on ALL optical sensors.

The thing is, the black and white wires carry the same data, just inverted. For example, if the sensor "sees" the target, the white wire will read "1" in the software, but the Black will read "0". If the target disappears, white will read "0" and black will read "1". It may be the other way around, but it really doesn't matter as long as you are consistent.

One possible use for using both: safety. If you use both wires, the corresponding values in PBASIC should ALWAYS be opposite. If for some reason they aren't, you know an error occurred with the sensor. This also you to distinguish between a sensor that has come unplugged and one that just doesn't see anything.

--Rob

P.S. Check out page 13 of the Robot manual. It's got all the info you need for sensor pinouts.

[seanwitte]

the responses explained very well how they work, just make sure you use BINARY inputs. Those are the equivalent of a switch, not an analog input.

[Dave Flowerday]

Originally posted by rbayer
One possible use for using both: safety. If you use both wires, the corresponding values in PBASIC should ALWAYS be opposite. If for some reason they aren't, you know an error occurred with the sensor. This also you to distinguish between a sensor that has come unplugged and one that just doesn't see anything.

Unfortunately this isn't necessarily true. We just verified earlier this week that all digital inputs are not sampled by the RC at the same time, so if you connect the sensor up like this it is possible that you will read both 1s or both 0s.

What we did to check this is to wire 8 digital inputs together to a momentary switch. We then modified our 2002 software to output the values of the switches using debug. Just manually flicking the switch by hand rapidly will result in one sample every few seconds that isn't 0xFF or 0x00, but is a random bit pattern.

[rbayer]

Originally posted by Dave Flowerday
Unfortunately this isn't necessarily true. We just verified earlier this week that all digital inputs are not sampled by the RC at the same time, so if you connect the sensor up like this it is possible that you will read both 1s or both 0s.

What we did to check this is to wire 8 digital inputs together to a momentary switch. We then modified our 2002 software to output the values of the switches using debug. Just manually flicking the switch by hand rapidly will result in one sample every few seconds that isn't 0xFF or 0x00, but is a random bit pattern.

Interesting. I guess this means there is no point to using both. Oh well, that just means more available digital inputs!