Problems with out power distribution board

[Jon Jack]

Hi All,

I wired up our power distribution board based on the wiring diagram in the control system documentation. When I powered on the robot to do our OTB tests, the power distribution board makes a squealing noise and the LED indicating the health of the 5V power supply does not turn on. When I unplug the gateway from the 5V rail the squealing stops.

Can anyone explain why this is happening? Could I have hooked up something wrong? Do I have a defective power distribution board?

[kbaker159]

Do you have something hooked up to the 5V supply? Is the squealing very loud? I know the 24V supply has a light squeal when it is under load sometimes. It sounds like a short to me, or a defective board. I hope you can get it fixed quickly

[Jon Jack]

Yes, I have the wireless gateway plugged into the 5V power supply. When I unplug the wireless gateway, the squealing stops, telling me that it has something to do with the 5V power supply.

[EVanWyk]

Jon -

Did you say that the WiFi gateway (WGA600N) is hooked to the 5V rail? The 5V rail is for the camera (Axis 206), and the 12V rail is for the WiFi (WGA600N).


The 5V rail will shut down if they are presented with a heavy load (in excess of 3A, roughly). The WGA600N only draws ~0.5A @ 5V when wired with the correct polarity. However, they will draw much higher currents if the wires are in backwards. To test, I attached one to a benchtop supply in reverse and slowly ramped voltage. At 2V, I hit a current limit of 2A. I did not wish to continue the experiment for fear of damaging my hardware.

It is possible that your WiFi is wired into the 5V output backwards. It will not cause any damage to the PD. Unfortunately, this may or may not cause damage to the WGA600N - I do not know. It is my hope that the 5V rail on the PD detected this as a short circuit condition and shutdown before damaging the WGA600N. Please use the wall supply and verify that the WGA600N is still functional.


How loud is the "squeal"?


Several of the power supplies will "squeal". This happens when they are lightly loaded. Since they are designed to work down to a very low input voltage, typical conditions are considered to be "light loads".

The reason for this is that the boost supplies are more powerful than they need to be for typical operation (so they can work well during the extreme conditions). This prevents them from working continuously at light loads, so they take short naps while they wait for the output voltage to drop so they may work again. This process occurs at an audible frequency that is dependent on the input voltage and load. Although it is annoying to those of us who still have our hearing, it is not an indicator of any damage.


Unfortunately, it is possible to swap the camera and WiFi and have both run. I say unfortunately, because neither of them works optimally in this situation. The WiFi will drop out at 6V instead of 3V. The camera is running outside of its data-sheet range, and will possibly reduce its longevity. To all teams: please be sure to double check this in your wiring.



Please let me know if helps. If it doesn't, use a multimeter and post both the battery voltage (measured at the PD's M6 shanks) and the unloaded voltage of each of the PD's supplies.

- Eric

[sfhs_robotics]

We have a similar problem as well. However, I am sure that our bridge and camera are plugged into the proper ports (12v, and 5v respectively). There is an audible whining while the bridge in plugged in that changes pitches as the bridge goes through its startup procedure. Also, our 5v led does not turn on, even though the port is giving out 5v (according to our multimeter) and the camera seems to be functioning properly. Does anyone know what is going on?

[Russ Beavis]

As Eric mentioned, the squealing noise on the 12V supply for the wireless adapter is normal. The sound should disappear with a fully-charged battery and a very-empty battery. The squealing only occurs in between those battery states.

If your 5V LED is not on but the camera is operational, my guess is that the LED was installed backwards on your PD. You may need to return your PD for repair/replacement (to FIRST? to DivSys? I'm not sure but your documentation should provide the details).

Russ

[EVanWyk]

We have a similar problem as well. However, I am sure that our bridge and camera are plugged into the proper ports (12v, and 5v respectively). There is an audible whining while the bridge in plugged in that changes pitches as the bridge goes through its startup procedure. Also, our 5v led does not turn on, even though the port is giving out 5v (according to our multimeter) and the camera seems to be functioning properly. Does anyone know what is going on?

Does the WiFi and the cRIO work? If so, you have a single fault - the LED on the PD is broken in some way. Otherwise, everything is working as expected.

The whine is known and expected, and is not indicative of any known fault.

[Jon Jack]

Okay,

I mis-spoke before when I said the gateway was plugged into the 5V supply. The gateway is plugged into the 12V supply and the camera is plugged into the 5V supply. They've always been plugged in this way, I just didn't have teh hardware in front of me when I made the original post.

Everything turns on and operates fine, as far as I can tell (I'm just now getting ready to run the benchtop tests). Since both the camera and gateway were turning on I tried batteries of varying voltages (one near dead, another just under full). The squealing stopped with the near dead battery and remained with the other.

Since everything is turning on just fine, and the squealing stops based on Russ' explanation of the squealing, I'm assuming nothing is wrong with either power supply but instead that the LED is installed backwards. Therefore not turning on.

I've asked Kate for a replacement, it'll be on its way on Monday.

[David Fort]

...squealing noise ...

If your 5V LED is not on but the camera is operational,...

fwiw, we have no 5V LED also, yet measure 5V on the connector. (we aren't using it yet).

And I note that all is quiet when connected normally, but we get a squeal if the power connector is removed from the cRIO yet the power distribution panel is still powered from the battery. This would mean that power is going to the breakouts on the I/O cards in the cRIO backplane, but not to the "processor" part of the cRIO.

David Fort
Mentor
Team 1001
Brush High School
Lyndhurst, OH USA

[Jon Jack]

As Eric mentioned above, the squeal is not a sign of a fault.

You're running power to the cRIO from the 24V rail, right? Also, make sure that the screw in the connector is not resting on insulation. We had a similar problem, but with power going to the breakout boards. When I further investigated it, it turned out that the WAGO connector was clamping on the insulation. We stripped the wire a little more and reseated it in the WAGO connector and everything worked fine.