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-   -   How should we wire the photoswitchs? (http://www.chiefdelphi.com/forums/showthread.php?t=88548)

koo_04 30-01-2011 02:44

Re: How should we wire the photoswitchs?
 
Well, rsisk and I have gotten them working just fine. Now we have an issue that the carpet seems to be reflecting more then the tape? We are completely unsure of what is going on. If someone can make/has a tutorial, video or typed with pictures, that would AWESOME. If I had gotten these to work myself. I would be making it.

PhilBot 30-01-2011 11:22

Re: How should we wire the photoswitchs?
 
You didn't say whether you tried unplugging the PWM cable to see if it stopped blinking, so I'm still not convinced that you don't have a wiring problem....

However, the black slot on the front IS the Callibrate adjustment, so you use this to set the sensor for your field. (I've not heard of a LEARN mode for this sensor.... but who knows).

Once you stop the flashing, Calibration is pretty simple. Put the sensor over the carpet. Turning the screw all one way should make the LED go green (this is the LEAST SENSITIVE setting).

Now position the sensor over the tape. Slowly turn the screw the other way until the LED switches to Orange. Turn it a little further, and then move the sensor over the carpet again, it should go back to green.

It may take some tweaking but you want to ensure that the LED is green over the carpet, and orange over the tape.

Note : My experience is that most students assume that "looking correct" IS "correct". I don't always track down credentials before answering a post, but base my reply on what's written. Sorry.

Phil.


Quote:

Originally Posted by CaptainKemp (Post 1011048)
As many people would assumed, looking correct is not just looking at it. I re-did my wiring a couple times and tried many different I/O Ports to see if I was wiring the power into the signal as many other people have said this. Reposting an old problem would be silly and thats why I didn't. The signal is going to the signal pin on the Digital IO Board (the innermost pin). The power is the same for all of the photoswitches coming from the Power Distribution Board. The white wire from the photoswitch is connected to the white signal wire on the PWM.

I was wondering if people knew anything about the teach mode because I was trying to find the calibration screw and turned the front black piece. Now when I turn it on it is always flashing between the yellow and the orange lights.

Thanks,

Morton


CaptainKemp 30-01-2011 12:24

Re: How should we wire the photoswitchs?
 
No its fine, I know where you were coming from. When i pulled out the PWM cables it did stop flashing but I checked the wiring again and the white wire goes to the white wire. I don't know where else the wiring could go wrong because it is only the white wire that is connected to the PWM and then to the D I/O.

Can you think of any other reason past the wiring that may cause that or is it just the wiring because otherwise I am at a loss for answers.

Thanks

CaptainKemp 30-01-2011 12:34

Re: How should we wire the photoswitchs?
 
Disregard my last comment. I found the problem. We had a bad PWM cable that touched the signal to the power which caused it to go into the short circuit protection state. We replaced the PWM cable and now its working fine.

Thanks all

CaptainKemp 30-01-2011 13:52

Re: How should we wire the photoswitchs?
 
Okay, so now that the wiring is fixed, our calibration is now not working.

We believe that we were not supposed to turn the tuning knob over the ridge on the circle but we did before we realized this. The one photoswitch that we did not do this to is now working perfectly but the other two are not.

Can anyone tell me how you would reset the calibration on the photoswitch, or how to calibrate it once you passed the ridge, or if the photoswitches are now broken beyond repair?

Thanks

Al Skierkiewicz 30-01-2011 16:39

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.

CaptainKemp 05-02-2011 12:39

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

keericks 10-02-2011 17:19

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.

Alan Anderson 10-02-2011 22:17

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by keericks (Post 1020097)
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.

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.

keericks 10-02-2011 23:30

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by Alan Anderson (Post 1020262)
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.

Exactly what we did today ... Works great!

Hugh Meyer 11-02-2011 11:08

Re: How should we wire the photoswitchs?
 
1 Attachment(s)
Quote:

Originally Posted by keericks (Post 1020097)
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.

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

PhilBot 11-02-2011 11:21

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by Hugh Meyer (Post 1020528)
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.
-Hugh

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?

Hugh Meyer 11-02-2011 11:37

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by PhilBot (Post 1020533)
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?

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

PhilBot 11-02-2011 11:39

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by Hugh Meyer (Post 1020540)
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

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

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

keericks 11-02-2011 13:22

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by Hugh Meyer (Post 1020528)
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

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.

Al Skierkiewicz 11-02-2011 13:55

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by PhilBot (Post 1020542)
OK, good... but do you know if it's "legal" :)

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

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.

AlDee 03-03-2011 23:55

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?

Al Skierkiewicz 04-03-2011 08:02

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.

bensherman 08-03-2011 12:36

Re: How should we wire the photoswitchs?
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1034457)
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.

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.


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