Pro. Dev. Board just blew up the first time I turned it on!!!

Wolverine69

· Several months ago I ordered a PDB and after receiving it I had to let it sit around here at home until just today due to the fact that I have been traveling a great deal with my new job.

· So I finally get around to opening up the bubble wrap bag, printing out the·documentation, reading it over very well, installing the BS2 that I removed from my BOE and hooking up the power jack to a 12-volt SLA battery (yes, I verified polarity was correct).

· The instant I slid the power switch to ON there was a loud POP and a mini-mushroom cloud rose from the first component that is located just below the power switch.·

· What in the world just happened?·

· Is the board repairable?

PJAllen

You whacked a tantalum cap, either due to reverse polarity or by exceeding its rated voltage with your "12-volt SLA battery".

"mini-mushroom cloud"··

Wolverine69

Like I said in the my first post, I checked the polarity.· I hooked up the battery to my power plug (salvaged from a wall charger) leads using the polarity indicating symbol printed on the board above the power jack.· Inner is Negative, outer is Positive.

The board itself has printed right above the power jack:· 6 - 12V .





Post Edited (Wolverine69) : 12/14/2009 3:23:48 AM GMT

Phil Pilgrim (PhiPi)

Wolverine69 said...
Inner is Negative, outer is Positive.

Um, you'd better check that again. That's opposite of every Parallax board I've ever used.

-Phil

Mike Green

You connected the power supply backwards. Usually the outer connector is negative and the inner connector is positive. There are some exceptions to this scheme, but they're rare. As far as I know, all Parallax devices have the inner connector positive. That would certainly account for the tantalum capacitor popping. You're lucky that the voltage regulators Parallax uses for most of their devices are used in automobiles and have built-in protection against connecting the power source backwards. The input capacitor can be replaced.

The PDB schematic (www.parallax.com/Portals/0/Downloads/docs/prod/schem/PDB-RevD-Schematic.pdf) does show that the inner conductor of the power socket is positive. The product description in the webstore also lists the power source as "center positive".

I'm not sure if the LM1084 regulator used in the PDB is reverse supply protected. The datasheet doesn't say. You'll just have to replace the capacitor and see if it works.

Post Edited (Mike Green) : 12/14/2009 3:43:56 AM GMT

Wolverine69

Standby everyone, I'll take a picture of my board and try to post it.

Wolverine69

OK, here's what the polarity symbol on my board looks like and is what I went by when hooking my battery up.

Mike Green

Don't bother. If you look at the enlarged picture of the PDB in the on-line catalog, it's clearly marked with a minus sign for the silk-screened outer conductor and a plus sign for the inner conductor. Yours might have the paint chipped off, but the documentation and the production silk-screen clearly document the proper polarity.

You can either replace the capacitor yourself or call Parallax Tech Support tomorrow. They'll probably have you ship it back for fixing and testing.

Your picture shows the standard symbol for power connection with the center conductor clearly marked positive and the outer conductor negative.

Wolverine69

Mike,

· I have no doubt now that I hooked the battery with the polarity reversed,· but I still think the printed symbol on my board appears to me to show the center conductor as Negative and the outer as Positive.· The actual Neg. symbol is in the dead center, while the Pos. symbol is outside the Neg. symbol..· That appears 'cleary obvious' to me.

· I don't understand how you can say my picture clearly shows the center conductor as Positive?



·

P!-Ro

The inner line is the center connection, with the positive sign above it. The rounded outside has the negative sign above and to the right.

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PG

Mike Green

@Wolverine69 - I can say it because that's how I see it and I have some years of experience. I don't get to decide anything for anybody else though. I don't work for Parallax. I'm just another customer. If you call Parallax Tech Support tomorrow, you'll find that they're nice people and more helpful than most tech support people elsewhere. I can't promise what they'll do, but they often offer to replace or repair stuff if you send it back to them. You may find that replacing the input capacitor will fix it.

Post Edited (Mike Green) : 12/14/2009 4:49:38 AM GMT

Wolverine69

Do you mean the inner line that looks exactly like a Neg. symbol??· And around the right side of that line/neg. symbol is an arc that circles around to the top where it ends at a positive symbol?·

In a way, this is kind of funny how we interpret the same thing differently.

I can see now what you guys are saying, but I took several looks at the symbol on the board for the first time today and thought it obviously indicated the center conductor was negative and disregarded the documentation, I figured it was not current for my board.

Wolverine69

Mike & everyone else,

· I'll call Parallax tomorrow at work and see what they have to say.

· I am curious though whether I'm the only person to ever interpret that polarity symbol incorrectly?

Bill Chennault

Wolverine69--

Does the area around the PDB's power regulator look anything like this one that I hooked up backwards?



My humble opinion is that your board, like mine, experienced a toasty death. (There was a nice explosion and a cozy fire.) I could not salvage it. I gave it to a friend of mine that knows quite a bit more about electronics that I do and he managed to get it to come back to life.

Good luck.

--Bill

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You are what you write.

Bill Chennault

Wolverine69--

If it helps any, I interpreted the symbol like you did. I wish I could blame my mistake on that mis-interpretation. I can't. Eventually, I figured it out and STILL hooked it wrong!

--Bill

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You are what you write.

skylight

My first interpretation when seeing wolverines image of the power connector was pos centre and neg outer but I can see how he and others might interpret it differently, perhaps the hyphen used to point to the centre contact that looks like a neg symbol should be omitted and the plus sign replaced in its place or make the hyphen look more like a contact by making it thicker and filled in?

Most experienced with electronics would interpret it the correct way but as this kit is used by a lot of beginners perhaps a change of labelling or warning labels attached are called for?

Phil Pilgrim (PhiPi)

The only difference between the printed symbol on that board and the usual printed symbol is the lack of a round dot at the center connecting with that central "dash". That would completely disambiguate the meaning of the connector. I suspect the omission happened when the films were made for the silkscreen during the board fab process and not when the board was laid out.

-Phil

MichelB

Wolverine69 said...

OK, here's what the polarity symbol on my board looks like and is what I went by when hooking my battery up.

The "-" below the "+" on the left of ")" is the Inner Conductor i.e. the inner conductor is positive.
Therefore )- is the Outer Conductor and is negative.
Moreover it's not possible to change polarity with the power supply 12 VDC 1 A Parallax 750-00007 recommanded for the PDB or delivered with StampWorks kit and for any other Parallax power supplies.

vaclav_sal

Post Edited (vaclav_sal) : 12/16/2009 2:50:27 PM GMT

Chris Savage

vaclav_sal,

Your post would indciate that the PDB design is not a well-designed circuit. The necessity to add a reverse polarity diode against the 1 or 2 customers who make that mistake would seem to indicate it is not a big problem. Ben Franklin, inventor of the lightning rod and experimentor of electricity is quoted as saying, "an ounce of prevention is worth a pound of cure". I think the idea here is to prevent making the mistake rather than trying to make every product foolproof. Nonetheless is a redesign is ever done for any reason I will consider it.

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Chris Savage

Parallax Engineering
Check out the new Savage Circuits TV!
·

dandreae

Wolverine69 said...

Mike & everyone else,

· I'll call Parallax tomorrow at work and see what they have to say.

· I am curious though whether I'm the only person to ever interpret that polarity symbol incorrectly?

Please contact me at 1-888-997-8267 and ask for Dave andreae.

Kind regards,

Dave






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Dave Andreae

Parallax Tech Support·

Leon

I always use a little circle to indicate the central pin on those co-axial power connectors.

Leon

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Amateur radio callsign: G1HSM

mikediv

Come on guys that's confusing as hell, I know that the center is + and the outer is Neg any of us that has been doing this for a while knows it and I can honestly say I just assume it to be that way , but in this guys defense "not saying he needs it" That would have confused me as well just looking at it quickly. ,,,Wolverine69 it should be a fairly easy fix if you can solder you do nto have to use a SMT part you can always replace it with same vale cap ,, But I would hope Parallax would help you out.

Peter KG6LSE

I assume Tip positive unless I see otherwise .... also I prefer to look witch side goes to the PCB ground plane ..... and if I know there is a canse I might toast a board with RP I my self add a diode in parrall with the input with a SMT fuse or super narrow trace ... putting the diode in series adds a V drop that in some devices can cause it not to work right ......

Peter KG6LSE

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"Carpe Ducktum" "seize the tape!!"
peterthethinker.com/tesla/Venom/Venom.html
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
LOL

PJAllen

It's a PDB, the "P" is for "Professional".

Obviously, it's not going to be P for Personal responsibility.
·

dandreae

mikediv said...
Come on guys that's confusing as hell, I know that the center is + and the outer is Neg any of us that has been doing this for a while knows it and I can honestly say I just assume it to be that way , but in this guys defense "not saying he needs it" That would have confused me as well just looking at it quickly. ,,,Wolverine69 it should be a fairly easy fix if you can solder you do nto have to use a SMT part you can always replace it with same vale cap ,, But I would hope Parallax would help you out.

I can assure you that Parallax will take care·of this.·

Dave

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Dave Andreae

Parallax Tech Support·

Whit

When in doubt - read the instructions.

http://www.parallax.com/Portals/0/Downloads/docs/prod/boards/28138-PDB-v2.0.pdf and http://www.parallax.com/Portals/0/Downloads/docs/prod/schem/PDB-RevD-Schematic.pdf

This is a good lesson for everyone - Nobody likes to see the smoke!

It is also a good lesson about Parallax's customer support - always excellent!

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Whit+


"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

Post Edited (Whit) : 12/15/2009 3:39:07 PM GMT

RiJoRi

I, too, was confused looking at the picture.
If I had a board and was confused, I would have ohm'd it out: find a ground point and checked which part of the connector has 0 ohms to it.

Parallax can redo the silkscreen, or hire some newbie engineers to scrape off the '+' & '-' signs, and paint new ones in:

+ -)- --

<grin>

Probably the easiest (and cheapest) would be to add a paper clarifying which is which.


--Rich

john hauton

I'm sorry to hear youve damaged your board. If you look at the circuit diagram (page 7 i think)

I dont see how it could be much clearer......sorry
regards· john

ihmech

Wolverine69, don't worry about it, I have made plenty of mistakes in my electronics hobby and let the "Magic Smoke" out of electronics. It happens, I used to have a lot of trouble with the same power jack symbol. As far as "Idiot Proofing" anything, my beleif is that idiot proofing breeds iresposiblility. If you can't make mistakes, how can anyone learn anything. Early in my profession, I made a $3,000 mistake that only took 4 seconds to happen. So don't kick yourself for your mistake and don't let anyone make you feel stupid about it. All I ask is that you learn from your mistake and move on, but remember to help someone else that might make that same mistake in the future. Take care and good luck with your repairs.