Problems with IR Board

[Tom Bottiglieri]

I feel like this is controlled chaos.

[DonRotolo]

Originally Posted by Tom Bottiglieri

I feel like this is controlled chaos.

Controlled?

Regarding 78L05 regulators: They are indeed short circuit protected, but that's only against a heavy short. Draw 150 mA from it for a bit of time and the magic smoke will come out quite easily. Short does not equal Overload. A 78L05 is not overload protected.

Don

[Mark McLeod]

An update...

FIRST exchanged our IR board and the new one works with all the remotes listed in my first post that passed the learning stage.


They drove all the way to my house to drop it off. Incredible service
Thanks Andrea and Kate !!!
(door-to-door service not available in all areas )

I did try a Sony based on Gdeaver's suggestion, but the model I had was rejected by the error LED. But if at first your remote doesn't succeed, try, try another one.

[Tom Bottiglieri]

Originally Posted by Tom Bottiglieri

I feel like this is controlled chaos.

Originally Posted by Mark McLeod

FIRST exchanged our IR board and the new one works with all the remotes listed in my first post that passed the learning stage.

I guess I was wrong. No cool broken supplies for an engineering project this season.

[Daniel_LaFleur]

Originally Posted by Ed Sparks

Hmmm.....

Says in the data sheet that these regulators have short circuit and thermal protection built in. In other words, given that the power source is within spec, you should not be able to destroy them (no matter what the load). Maybe some were accidently powered up with reverse polarity at some point. I'm leaning toward the explanations in Daniel's list.

Thanks.

The short circuit protection in this chip is a current limiter circuit. That said, the chip wont survive prolonged usage at max current (>140mA).

The Thermal protection is also a short term stopgap measure. The output current is driven by a FET which as it heats up provides lower current. This will slow down the heating process but will still fail if the chip is allowed to continously run at high current.

I've never really had issues with a National Semiconductor chip. They tend to be much more robust that some of the other knock off chips. Makes me wonder if something else on the board is drawing too much current.

[keen101]

Is this going to be a problem when running off our robots on 12 v batteries, and probably at max current for long periods of time?


Will one of those auto-resetting breaker fuses protect this?

[Aren_Hill]

Any advice on what to do if we've fried the 5v regulator?
Should we replace it, or wait for more info from DIVSYS

[Daniel Bathgate]

Update: We reversed the LEDs on our board (with FIRST's blessing), and now it works great. Hopefully backwards LEDs was a fluke limited to our board.

[DonRotolo]

Tally so far:
358: LEDs flash during learning. After, either error light or nothing. Replacement board works fine.
456: Totally dead, 78L05 has no output
1357: Worked, then 78L05 fried. Maybe anti-static bag?
1625: Fried regulator??
2144: Board works, LEDs do not light. Reversed LEDS (with FIRST's blessing) and all is well.
2199: Error LED lights sometimes, not "0" (learn loop) LED

Aren_Hill: So far the advice has been to inform FIRST and NOT to replace it yourself.
Please elaborate: What makes you think the regulator is fried??

Don

[Daniel_LaFleur]

Originally Posted by keen101

Is this going to be a problem when running off our robots on 12 v batteries, and probably at max current for long periods of time?


Will one of those auto-resetting breaker fuses protect this?

If the boards were designed correctly (and as of now I have no data to support otherwise) then the regulator should not be running anywhere near max current, and therefore should be fine.

The 12V from the battery is well within the specifications for input power for the chip (36V max, 7-15V nominal).

Unfortunately the auto reseting breakers will not protect this device as the smallest of the auto resetting breakers are 20 amps and the board is speced for 100mA max normal usage and 140 mA catastrophic current.

Again, as of now, we've only heard of a few failures. Lets take tallies of whats failed and why. At this point we should still be in information gathering mode and not jumping to any conclusions.

[Aren_Hill]

We visually saw smoke rise from it. and the board appears melted by the back of the 3 pins of the regulator. and after that it doesn't work, so my diagnosis is the regulator fried

[DonRotolo]

Pretty conclusive...

[billbo911]

Originally Posted by Aren_Hill

We visually saw smoke rise from it. and the board appears melted by the back of the 3 pins of the regulator. and after that it doesn't work, so my diagnosis is the regulator fried

FYI, All electronic components use smoke and mirrors. If you let out the smoke, they're broke. If you break the mirrors,.....darn, no rhyme.

You get the picture.

[Chris_Elston]

1501 IR board works great out of the box.

[Jim E]

Speculation:

Hmmm. Having not seen the board yet, It does appear a problem exists with the 5V regulator load.

One could measure the resistance between the output pin of the regulator to ground to determine if a short is there before power is applied.

Look the board over closely before applying power. Use a magnifying glass or microscope. Make sure the solder connections are good and sound. A good lead-free solder connection will appear slightly grainy. Any connection a dull, bumpy gray is suspect. Also check to make sure the pins are actually making contact to the pads. Sometimes it looks good, but oxidation or lack of flux will cause an open connection.

Lead-free (RoHs) solder does require higher temps in the reflow oven. Many companies are scrambling to overcome this obstacle. If the part is not designed for RoHs solder techniques, it may not survive. National Semiconductor's new stock has been RoHs compliant for years.

Hopefully, the problem is not in the PCB traces themselves. A short in adjacent traces will be impossible to repair if it occurs in internal PCB layers.