Problems with IR Board

[Kevin Sevcik]

EDIT: Disregard the next paragraph...

I'm thinking this might be an oversight in the circuit design. The 78L05 series of regulators are rated for 100mA max output current. And the IR manual claims the circuit draws 100mA when an LED is on. Granted, that's a transient draw and the things are rated for occasional current peaks above that, but if it's been derated from overheating during the soldering process, then it could be marginal.

Of course, something could have just been shorted while you were testing it or something. At any rate, you should be able to find a 78L05 regulator of some brand at a local electronics shop that actualy carries things like resistors and caps and such. If you can find a 7805 or 78M05 regulator in a TO-220 package it'd probably be hardier, but you'd have to really try to jam it in to the same footprint, and heaven knows if any of this will be legal come kickoff.

EDIT: Whoops! I must have misread the IR manual, current draw is certainly not close to 100mA....

[keen101]

as far as how mine died... It shall probably always be a mystery.

Maybe something shorted, but I think overheating is more likely. I had been playing with it for over an hour. Enough time to overheat?

Besides... I didn't think anything could short out on an anti-static bag. Who knows, maybe my finger slipped and shorted something. seems dubious though.

[MrForbes]

beeing over 40, I had to take a picture of the part to be able to read the writing on it!

[Daniel_LaFleur]

Originally Posted by squirrel

beeing over 40, I had to take a picture of the part to be able to read the writing on it!

Looking at your picture, the part is made by National Semiconductor (thats the funky looking 'N' as the first letter) .

A quick search found a data sheet here ( http://www.national.com/ds/LM/LM78L05.pdf )

While they are ESD sensitive devices, they tend to be rather robust so a little handling should not hurt them very much.

There are a number of things that these little guys dont like:
1: Input power and ground reversed. So watch your polarity when applying power.
2: Voltage on the output being driven higher than the input voltage. This typically only happends with some sort of inductive kick, but ...
3: Applying more than 35 Volts at the input. Some power supplies (especially older ones) may spike when turning on. Check your power supply with an o'scope to see if it spikes (DMMs don't read fast enough).

They can be bought here http://search.digikey.com/scripts/Dk...M78L05ACZNS-ND

[Ed Sparks]

Originally Posted by Daniel_LaFleur

Looking at your picture, the part is made by National Semiconductor (thats the funky looking 'N' as the first letter) .

A quick search found a data sheet here ( http://www.national.com/ds/LM/LM78L05.pdf )

While they are ESD sensitive devices, they tend to be rather robust so a little handling should not hurt them very much.

There are a number of things that these little guys dont like:
1: Input power and ground reversed. So watch your polarity when applying power.
2: Voltage on the output being driven higher than the input voltage. This typically only happends with some sort of inductive kick, but ...
3: Applying more than 35 Volts at the input. Some power supplies (especially older ones) may spike when turning on. Check your power supply with an o'scope to see if it spikes (DMMs don't read fast enough).

They can be bought here http://search.digikey.com/scripts/Dk...M78L05ACZNS-ND

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.

[GaryVoshol]

If anyone is going to modify/fix this board, wouldn't the work have to be done AFTER kickoff?

[nautica]

Our team successfully trained the chip today.
All we did was follow the instructions about pressing the buttons.
We were able to light up the LEDs using channel buttons (1-4) on a universal TV remote.

Tally so far:
358: LEDs flash during learning. After, either error light or nothing
456: Totally dead, 78L05 has no output
846: LEDs flash during learning and afterwards when controlled by remote.
1357: Worked, then 78L05 fried. Maybe anti-static bag?
2144: Board works, LEDs do not light
2199: Error LED lights sometimes, not "0" (learn loop) LED

[keen101]

Heh. Maybe people should start using the numbers that Don supplied as error numbers.


for example: I had a "1357 error" on Wed.


Tally so far:
358: LEDs flash during learning. After, either error light or nothing
456: Totally dead, 78L05 has no output
1357: Worked, then 78L05 fried. Maybe anti-static bag?
2144: Board works, LEDs do not light
2199: Error LED lights sometimes, not "0" (learn loop) LED

............

Then again... maybe not. I don't know if it would help or not.

[Mark McLeod]

Please focus this thread on issues with the board only.
Can be failures, potential ways to kill the board, or just interesting unreported behavior, such as, getting the LEDs into a chase sequence.
Let's assume most of the boards operate normally, and we're looking for that 1%.

I added a thread with a poll where we can report that our boards are working great!

Please don't repeat the talley if you haven't added your team to it. Otherwise it just takes up space.
We're looking for added value.

I'd like to avoid a 1500 post chatty thread of who's board works.

[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.