DLink / D-Link resets going over bumps! Thoughts?

Technical Electrical
#15

This probably isn’t your problem, but just for the record we had hellish problems last year losing connection. This persisted through two regionals. Our drivers spent more time with their hands in their pockets than on the controls.

After getting back and experiencing the same problems on a completely different robot we investigated further.

We found vigorously shaking the radio had NO effect, but gripping it lightly on the top and bottom killed it instantly! We took it apart and looked at it under a magnifying glass for aluminum shards, cracked traces, anything. Finding nothing we put it back together and it worked just fine. Go figure.

That’s why I’m a mechanical guy.

#16

I just got through purchasing another DLink because our team wired it directly and fried it. $107.00 from Office Depot because we didn’t RTM! Please learn from our eagerness to get the robot rollin’!

#17

If you are loosing something when you run over bumps check these things…

  1. lightly tap the red button on the main breaker. Do lights on the robot flicker? Replace main breaker it is defective.
  2. Does your cRIO move around? It may be shorting to the frame of the robot when it moves. Some RS770 motors are being delivered with a short to case. If you are using these motors check continuity from each motor terminal to motor case. You may be sending power hits to the Crio.
  3. Triple check the power wiring coming from the radio connector on the PD. These are notorious for being improperly terminated. The wires should not pull out when tugged and there should be no visible whiskers that can short the two wires together.
  4. Check that the battery terminals on the PD are snug and have a lockwasher under the nut that hold the terminals in place.
  5. Check the battery connections by moving all #6 wire with the robot turned on. Flickering indicators are a sign that something is loose.
#18

Any body ever heard of a converter that is bad? On our converter, when we power 12v in we get 7.3v out. That doesn’t necessarily concern me, what does concern me is that when we plug in the power to the D-Link we get nothing; we tested voltage, and we exactly get 7.3v out of the plug (as expected - the plug that came with the D-Link gives 5.2v in the same orientation) yet the D-Link is only pulling 2mA from the converter. Something seems bad here…

We do know:

  1. If we bypass the converter, everything “works” (we accidentally did that before adding in the converter). This tells me the extra plug we bought (same size as the one that came with it) fits and works.

  2. If we plug in the power cable that CAME with the D-Link, everything works fine (even after the fact).

  3. With the converter in-between, voltages look fine but we’re pulling almost no current.

Does this sound fair to say the converter is possibly bad?

-Danny

#19

That does sound suspect, I remember when we wired ours up I probed it with the multimeter before connecting the radio to confirm polarity and it was reading around the expected 5V under no load. Some SMPS don’t work well without load, but if you’re connecting it to the router and not getting anywhere, that’s weird.

Are you sure your router is good? It seems strange it wouldn’t try to pull more current. If the problem was in the converter not delivering more current the voltage should take a dive.

Matt

#20

What about that button on the side of the D-link? (I believe it has circling arrows) Is it getting pressed when the robot hits a bump in the carpet? Could that be resetting the D-link in some way?

#21

Last year we had a similar problem with communications. We lost it every time we went over a bump! It is still a mystery for the most part, but I am sure that it was the terminals to the battery. The few times we didn’t lose communications were matches where we cleanly redid the leads to the battery beforehand. I’m sure the battery box was also to blame. It was solid and kept a strong hold on the battery, but the whole thing swung around as the robot moved, which probably loosened the leads.

#22

Last year we velcroed our black bridge on, kept the battery in place with surgical tubing, screwed in a bolt for the battery connector end attached to the Power Distribution Board. I don’t think we had any problems last year during a match related to communication.

#23

Danny,
There are two things that concern me. The first is that the DAP works on 12 volts when you bypass the convertor. This should not happen, it should blow up the DAP at 12 volts. The second is that you are measuring 12 volts into the convertor but only getting 7.3 volts out.
I have to ask (even though I know the answer) is the convertor wired exactly according to the drawing. The +12 volt radio connector on the PD wired to the convertor input leads and the DAP connected to the output leads?

#24

That’s what I thought, too, and nearly had a heart attack when I was reviewing the schematic and saw the need for the converter. Eric VanWyk looked over the components inside the DAP, and he says all of the power components should be capable of handling 12v but the manufacturer of course will not sign off on that (for good reason). After plugging in the DAP into 12v, I was concerned I may have fried something, but when we plug the DAP into the wall using the supplied transformer/cable it works flawlessly (at least as flawlessly as we can tell). I think we’re going to get a new DAP and have it stand-by just in case something turns up, but we cannot find anything wrong with the one we have.

That’s a fair question, but I wonder why you said, “only getting 7.3 volts out” - when I saw 7.3v when we first started playing with it I thought that was pretty suspect since I figured we should be seeing something around 5v since the converter is a 12v/5v converter. We absolutely have the converter’s 12v input line connected correctly to the PDB’s 12v output just to the left of the 24v line for the cRIO (and we’re correctly measuring 12.3 volts from that line), and then the supposed 5v output (from which we’re measuring 7.3 volts) from the converter is wired correctly to a connector that plugs into the DAP’s power plug (EDIT: Yes, and we have a fully-charged battery).

It’s just that when we try to power the DAP through the converter, nothing happens - no lights, no nothing, and while plugged in the multimeter says 2mA when I cut one of the wires and put the multimeter in series between the cut. But, when we unplug from the converter and use the supplied walwart (plugged into the wall, of course) everything works great on the DAP.

-Danny

#25

Just curious, are you able to measure the current draw and the voltage at the same time? it seems odd that you’d be pulling so little current at 7.3V. Like I said before, I’d expect the voltage to dive if the converter was damaged, other than that I would agree it sounds like a faulty converter.

Worst case, you could design an elaborate mechanism to trail an extension cord to your robot :wink:

#26

While one multimeter was reading the 2mA with the plug trying to power the DAP, we used another multimeter to verify the voltage going INTO the converter, and saw we were still getting 12v INTO the converter - I remember saying out loud, “now we need to measure the voltage coming OUT of the converter,” but because the “other” solder joint was still heat-shrinked for the output side I think it was quickly forgotten. Thanks for the reminder, I’ll do that today.

-Danny

#27

If the voltage is low as I suspect you may have a bad converter, or when you attached your ends and did the heatshrink you got a short, and the converter is shutting down to prevent damage. (Do we know if it has this feature?)

If it doesn’t have such a feature it might be that you have a bad converter because of a short damaging it. I’d definitely double-check all your connections in this case and make sure there are no shorts and see if that resolves your problem.

If you measure a high voltage (like 7.3V or so) at that current… I’m flabbergasted?

I wouldn’t personally be too concerned about the 7.3V, some SMPS and even linear regulators float high without load, just because it didn’t occur when I checked it doesn’t mean it won’t.

Do report back please, I’m curious how this works out,
Matt

#28

Tis a puzzlement.
I would have guessed that the failure mode on this device would a zero volts or 12 volts. Since it is not zero, 7.3 seemed to be low. I have not found any real data on this device on the manufacturer’s website so there is no way to point at a particular type of convertor. So I am going to say it is defective but this is what I think might be the failure. If it is a switching type of regulator, the frequency might be so far from design that the output is not able to generate any current. Have you looked at the output with a scope? I am guessing there is a fair amount of AC voltage on the output and your meter is measuring that and interpreting it as 7.3 volts DC.
Of the teams that have reported that they hooked up their DAP to 12 volts and killed it, some may have reversed the voltage prior to the connection. Maybe you are just super lucky. With that kind of luck, I hope we don’t play against you this year.

#29

Hmm, interesting theory, I hadn’t thought of that. I’m quite curious now, I wonder if they have a scope.

Matt

#30

I started this two days ago. Yesterday, we had a short round of testing where the original DLink (DLink-1) was used and though the power cord was tethered such that the barrel plug would not move - we still had our issue of it resetting. We also did a good job of using a glue gun on the barrel plug (power cord) and still the issue persisted.

Tonight, we tested this again but instead of the original DLink-1, we used a 2nd one (DLink-2). Worked just fine till the our battery casing and battery fell off! We have a piece of carpet rolled out in the hall and we placed chunks of 2x4 underneath the carpet. The robot hopped around all over the place. The ‘reset issue’ didn’t occur. Once we fixed the battery, we proceeded to test.

DLink-2 seemed to work fine. Though, we might have had some lag issues.

Replaced the DLink-2 with the DLink-1 and though the reset issues didn’t occur again, the robot exhibited some lag where the driver tried driving but the robot would not respond for a up to five seconds at a time. Not sure if we have a different problem or the same one.

Tomorrow, we plan to do the same bumpy-carpet testing with both DLinks mentioned as well as a 3rd one (DLink-3). Hope to report back some findings.

Suggestions for any type of specific tests to run? I figure we had the symptoms with lumpy carpet. I’m not sure what to do about the ‘lag issues’ since we don’t have a camera mounted and I’m not sure if it’s interference with the battery and electronics. I saw another thread that suggested placing the DLink about two feet above the electronics.

#31

If I haven’t said this yet (and I don’t think I have), sorry Ted, I didn’t mean to hijack your thread. :wink:

We did the test today, and with the DAP power plugged in we again read 2mA being sourced, but when we’re sourcing current from the 5v output the voltage on the converter drops from 7.3V to 4.0V. We’re satisfied with calling it “blown”, and we’ve ordered a replacement (2 actually). What’s really cool is that the 5v output on the PDB works wonderfully to power the DAP, and its maximum current draw is only .5A higher than the camera - we’re not even using the camera this year (programmers decided they had enough to chew on given the control challenge they were given for the rest of the bot), so we’ll just keep using that until the new converter comes in (too bad that’s not competition legal).

The only thing that interests us is that before we realized the converter was required for powering the DAP, we were using the converter as a benchtop 5v power supply for testing 5v sensors using competition batteries as power sources, and the tests all seemed successful (and the sensors draw about 60mA) - the tests are no longer successful, we cannot power squat. Perhaps the 12v input got its polarity swapped incorrectly once or twice, causing the converter to blow? That would be a crappy converter for sure without polarity protection. Anyone know if the device has polarity protection, I couldn’t find any real specs on it to determine this. I do know that in its current configuration if you reverse its input polarity the 5v output drops from 7.3V to 0.2V until you swap the polarity back again (we just HAD to test it).

-Danny

#32

The DAP seems to have a switching voltage regulator inside it immediately following the power input, so I’m not surprised it worked.

~David

#33

Ted,
It is best to mount the DAP-1522 away from motors and large metallic objects but two feet from electronics is kind of extreme. There should be very little lag in controls with this device. Are you getting any indications of loss of signal, dropped communication, etc.? Does the robot run correctly if you tether through the DAP? (That is an extra added feature this year. You do not have to disconnect the wireless to tether.)

#34

Oh goody, we’re back in the land of sensible result! :slight_smile:

You had me really wondering for a while, sorry your converter is toast, but it sounds like everything’s gonna work out for you. Maybe when testing sensors your converter got shorted by accident? Since it’s a vital part of the robot and we’re down to under a week, I’m sure not going to try shorting ours out now to see what happens!