Broken Beam Sensor?
 

Our team needs a way of seeing if we have a ball in position to be kicked or not and a broken beam sensor or something similar seems like it would be perfect. Could someone recommend one that is compatible with the control system and is legal for FRC?

Re: Broken Beam Sensor?
 

We used a garage door sensor with a bit of custom electronics to give us a digital signal. The mentors said they couldn't find any rules against it.

Re: Broken Beam Sensor?
 

we too are using a garage door sensor

Re: Broken Beam Sensor?
 

We are using a IR broken-beam sensor, no idea where we got it from (Jim says he's had it for a while), seems to work great, thats all I can say on that.

As for the rules, there are some rule regarding sensors. Not many. They are categorized as custom circuits, so <R03> says what custom circuits can and cannot do (you can't directly drive a motor or use any wireless communication), <R45> says where they can get power from (20 amp breaker on PD board or 5v supply on DSC or Analog board), <R64> lets you put them on a CAN bus, <R68> tells you where you can connect their outputs (More custom circuits, DSC, Analog board, Serial port, Ethernet 2 port, CAN bus). The only other rules regarding sensors are the size and weight limits. Basically, if you can find a sensor that runs on 12 of 5 volts and outputs a digital signal (TTL or open collector)

Re: Broken Beam Sensor?
 

We use the Banner QS18VN6LV sensor.
It is a red light sensor, so you can see the beam.
You put a patch of retro-reflective tape on
the other side where the beam hits.

Brown wire goes to 12 volts,
blue wire goes to ground of the digital input
black (or white) wire goes to signal.

The sensor costs around $60 last I checked.

Eugene

Re: Broken Beam Sensor?
 

You can use just about any input sensor you wish. It is outputs that the rules are much more concerned with.

Re: Broken Beam Sensor?
 

The BANNER Sensors mentioned above are great sensors.

For this application you may also want to consider a current sensor on the roller/vacuum motor, then you dont have to worry about placing a beam sensor or reflective tape or anything like that. (if you have no active possession mechanism ignore this comment)

Re: Broken Beam Sensor?
 

Depending on the application, an encoder could work as well. It would detect a drop in speed that comes with acquiring a ball. The beam sensor seems like the best solution. It is simple, requiring only either an integrated sensor and reflective tape or a separate emiter/reciever, and feeds the output straight into a DIO pin. Plain and simple: a boolean value that tells you flat out DO I HAVE A BALL OR NOT? even if the ball is only sorta on your collection mechanism or the roller isn't running.

As for setting up the sensor, I recommend you power up the robot and look at the sensor output while mounting it. This can tell you if you have everything lined up and the software can see it.

Re: Broken Beam Sensor?
 

A Banner QS18VN6LV looks absolutely perfect. However, do we have to be concerned about:

<R02> ROBOT parts shall not be made from hazardous materials, be unsafe, or cause an unsafe condition. Items specifically PROHIBITED from use on the ROBOT include (but are not limited to):
A. Shields, curtains, or any other devices or materials designed or used to obstruct or limit the vision of any DRIVERS and/or COACHES and/or interfere with their ability to safely control their ROBOT
B. Speakers, sirens, air horns, or other audio devices that generate sound at a level sufficient to be a distraction or hindrance affecting the outcome of a MATCH
C. Any devices or decorations specifically intended to jam or interfere with the remote sensing capabilities of another robot,including vision systems, acoustic range finders, sonars, infra-red proximity detectors, etc.(e.g. including imagery on your robot that, to a reasonably astute observer, mimics the VISION TARGET)
D. Exposed lasers of any type (COTS devices with completely enclosed integral lasers, such as a laser ring gyro, are permitted)
E. Flammable gasses
F. Any devices intended to produce flames or pyrotechnics
G. Materials that off-gas noxious or toxic gasses
H. Materials that produce hazardous inhalable particles
I. Caustic chemicals
J. Hydraulic fluids or hydraulic components

Re: Broken Beam Sensor?
 

The WorldBeam QS18 series uses conventional LEDs, not lasers.

Re: Broken Beam Sensor?
 

Incorrect according to this, although the exact model above does use LEDs.

Please be careful when making assumptions about parts.

Re: Broken Beam Sensor?
 

Interesting. When I looked this up a few years ago, I remember all the laser-using parts having a QS6 prefix. I must have been looking at a different catalog, or perhaps I am just confused. :confused:

Re: Broken Beam Sensor?
 

Please do be careful when ordering banner sensors, I don't remember
laser based QS18 parts, but there they are now, with the usual warnings.

http://stevenengineering.com/pdf/04PHOTO_QS18.PDF

The led based part I listed has more than adequate range for
a beam breaking sensor for internal ball detection on a robot.
It is also quite useful to detect a given position on a rotary
shaft, such as one might use to pull back a kicker. Limit
switches tend to get mangled.

The FRC rules proscribe lasers for good reasons and the laser
based banner sensors would be proscribed at a FRC event for
these same reasons.