Line Sensor hookup

[Dinush]

On the controller, it says that the Digital I/O ports have a grnd a +5V I/O. However, the output on the line sensor outputs at 12 V. Will it be okay to connect the white wire directly to the digital in? Has anyone actually done that?

[Venkatesh]

Originally Posted by Dinush

On the controller, it says that the Digital I/O ports have a grnd a +5V I/O. However, the output on the line sensor outputs at 12 V. Will it be okay to connect the white wire directly to the digital in? Has anyone actually done that?

We have been experimenting with line tracking and the 2004 controller since week 2. Here is how we have wired it up. The desired signal wire (white/black) from the banner sensors are plugged into the RC's digital inputs, the signal port. The ground wire from the sensors (blue, if I remember correctly) are connected to the ground port on the controller. The power line to the sensor cannot be plugged directly into the controller. The sensor requires +12V to operate. We powered it off the main breaker block, through a 20A circuit breaker.

As a side note, the white and black cables carry signals which are just NOTs of each other, so either one can be connected to the signal line of the RC. Also, the light sensors may power up from the +5V line of the RC, but they will not function reliably.

Good luck with line tracking! It is serving us well over here.

[Dinush]

I was also wondering what we use to connect the line sensor wires to the pins on the controller.

[Venkatesh]

Originally Posted by Dinush

I was also wondering what we use to connect the line sensor wires to the pins on the controller.

On our robot, we used 20 gauge wire. However, the wire from PWM cables proves extremely convenient to work with, and the fact that a female cable header is already available on one side would let those cables work well.

I believe that FIRST rules require a minimum of 24 gauge wire to/from sensors. I don't believe that rule is modified by the fact that the light sensors require +12V as a source.

[blindguyinanorg]

Originally Posted by Venkatesh

We have been experimenting with line tracking and the 2004 controller since week 2. Here is how we have wired it up. The desired signal wire (white/black) from the banner sensors are plugged into the RC's digital inputs, the signal port. The ground wire from the sensors (blue, if I remember correctly) are connected to the ground port on the controller. The power line to the sensor cannot be plugged directly into the controller. The sensor requires +12V to operate. We powered it off the main breaker block, through a 20A circuit breaker.

As a side note, the white and black cables carry signals which are just NOTs of each other, so either one can be connected to the signal line of the RC. Also, the light sensors may power up from the +5V line of the RC, but they will not function reliably.

Good luck with line tracking! It is serving us well over here.

do the both have to be plugged in to work properly??? just want to double check before i come across unknown errors

[Mark McLeod]

Originally Posted by blindguyinanorg

do the both have to be plugged in to work properly??? just want to double check before i come across unknown errors

No, just pick one of the two.

[Al Skierkiewicz]

Originally Posted by Dinush

On the controller, it says that the Digital I/O ports have a grnd a +5V I/O. However, the output on the line sensor outputs at 12 V. Will it be okay to connect the white wire directly to the digital in? Has anyone actually done that?

All,
This is one of those confusing issues in electronics. The sensors reguire 12 volts but the output is not 12 volts. The output circuitry is actually two transistors whose collectors are the output pins. They require a pullup to a voltage from the device they are feeding. In this case the pullup is built into the RC and "pulls up" to 5 volts, the RC power supply. The two outpus are electronically opposite of each other such that one is "on" when the other is "off". When an output is "on" the transistor conducts to ground and so acts like a relay or switch closing a circuit to ground. When connected to the RC current flows from the RC power supply through an internal resistor to the output lead of the sensor and then to ground. The internal resistor limits the current drawn from the internal power supply.

[blindguyinanorg]

another ? can i hook all the sensors to the same ground. it would make thinks a bunch easier

[jacob_dilles]

okay this is being made more confuzing then it is. you feed the sensors +12 and ground in the red and brown blue wires. you can then connect the signal wire you want (nc/no) to the RC digital inputs. they are already pulled up for you at 5v so you dont have to do any work. i would ground the sensor sepretly then from the pin on the RC, but it realy doesnt matter

[Al Skierkiewicz]

Originally Posted by blindguyinanorg

another ? can i hook all the sensors to the same ground. it would make thinks a bunch easier

We don't think it makes things easier. If you are making your own plugs, you want the extra pins in place to hold the connector body on the RC pins. If you have modified a PWM cable to splice to the sensor, you would want to have a single cable in case the PWM cable goes bad. For best noise isolation, it is best to run a parallel ground lead with the sense lead since the flow of current is from the RC power supply back to the RC ground system.