Re: How should we wire the photoswitchs?
 

Morton,
I am guessing by your description that you turned the adjustment pot past the mechanical stop. There are two outcomes for this, one being you broke the pot. The second is that you broke the plastic knob that connects to the pot. Neither of these is repairable.

Re: How should we wire the photoswitchs?
 

Thanks Al,

I looked at the knob and you were right, the knob was broken. I popped it off though and now I am able to calibrate the photoswitch with a phillips head screw driver and everything is working fine.

Thanks again everyone

Re: How should we wire the photoswitchs?
 

Understand the wiring setup for these things 100% based on the great thread here ... I was wondering if you could gang all three photo switches (brown & blue wires) onto a single 12V PDB (red/black) using either a terminal block or solder splice.

Basically, the three blue sensor wires ganged together and spliced with single 18AWG run to PDB ground. Same for three brown sensor wires to partner PDB 12v. run.

Re: How should we wire the photoswitchs?
 

That should work fine.

If you're feeling adventurous, you can even use the three wires of a single PWM extension cable, one from each of the sensors, and plug the connector sideways onto three adjacent DIO signal pins.

Re: How should we wire the photoswitchs?
 

Exactly what we did today ... Works great!

Re: How should we wire the photoswitchs?
 

Kent,

You may want to consider powering it with 24 volts. One of the updates makes it legal by connecting the sensors to a solenoid output on the cRio and powering that module from the 24 volts from the PDB.

Previously in this thread I posted a plot of typical voltage during a match. The sensors are good down to 10.8 volts and we regularly see voltages below that.

Attached is the data sheet that shows the working voltage range of the sensor.

-Hugh

Re: How should we wire the photoswitchs?
 

Although it's hard to determine if you can only power one Line sensor per Solenoid output. (We'd like to power all three from one output)

Since you can only power ONE soelenoid breakout with 24V, you may find yourself running out of solenoid outputs...

eg: 3 double acting solenoids will consume 6 outputs, leaving only two to power the three line sensors.

Question: How does the load of one Line Sensor compare with the load of one Solenoid?

Re: How should we wire the photoswitchs?
 

Phil,

We are running all three sensors on one output. It seems to be fine.

Don't forget you need to have the software turn on the output in order to turn on the sensors.

-Hugh

Re: How should we wire the photoswitchs?
 

OK, good... but do you know if it's "legal" :)

Yes... turing in the output is a good idea :)

Re: How should we wire the photoswitchs?
 

Hugh ... thanks for the feedback. I did see that update and thought about doing just that, but then figured that:

1. Calibrating the sensors without the robot being enabled to power up the Solenoid module would be a challenge.

2. We are only using the sensors in Autonomous where our battery would be at its highest - hopefully not dipping below the 10.8 during that time.

3. If we do have problems after testing for awhile - we can easily relocate the power feed to the cRIO module.

Re: How should we wire the photoswitchs?
 

Yes to both. You may splice all line sensor power wiring together and insulate with heatshrink or tape or you can use a terminal block as supplied in the KOP.

Re: How should we wire the photoswitchs?
 

Hi Everyone,

Thanks for all the info on this post. I've been able to gather a lot from here and the National Instruments site. Just want to make sure I have the info correct.

1.)The signal outputs of the sensors should go to the Digitial I/O, and no pullup is needed because the I/O card has built in pullups.

2.) It is safe to connect the signal to the Digital I/O, despite the higher voltage supply because the outputs are open collector.

3.) The Sensors can be powered by the 12V supply, but it may dip below the minimum 10.4 volts.

4.) Based on the ruling, one Solenoid breakout may connected to the 24V output, and a solenoid output can be used to power the sensors.

5.) Sensor supply lines may be spliced together (Or connected to a terminal block.) and connected to one 12V line, or one Solenoid output.)

It seems like the 24V option would be the better way to go, but I have one question. It seems to me that since the line trackers are only used for autonomous, what are the odds of the battery dipping below 10.4 volts during this 10 second period? Has anyone tested this and seen it fail with a fresh battery? Just wondering if the "Quick and dirty" method of using 12V, will suffice for practical purposes.

On a different note, does anyone know if the 24V ruling was done to accomodate the 24V solenoid that shipped in the KOP?

Re: How should we wire the photoswitchs?
 

Al,
Correct on all counts. To add one thing, the power lines need insulation in some form. A terminal block handles this nicely, insulated splices also work.
The chances of going below 10.4 volts is a guaranteed condition when ever you start to move. If like most teams, you are using 2-4 CIM motors, the current at start is enough to drop a couple of volts across the battery internal resistance. Add wiring losses and you will find that the power to the sensors if going to be near drop out a lot of the time.

Re: How should we wire the photoswitchs?
 

For our wiring, we have the positive and negative from each of the three sensors w/ 15 amp anderson connectors on them. Then, we have a main pos and neg wire that goes into the pdb w/ 3 soldered positive leads on it (also anderson connectors). The reason for this is that you can power all three from one port on the PDB w/ a 20 amp breaker, and the andersons allow for easy swapping of the sensors. Lastly, we have the white wire from each with a PWM connector to go into the digital sidecar ports. The black wire was cut off as we don't use it. This configuration worked perfectly for us during testing and in competition.