Pro. Dev. Board just blew up the first time I turned it on!!!
· 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?
· 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?
Comments
"mini-mushroom cloud"··
The board itself has printed right above the power jack:· 6 - 12V .
Post Edited (Wolverine69) : 12/14/2009 3:23:48 AM GMT
-Phil
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
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.
· 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?
·
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PG
Post Edited (Mike Green) : 12/14/2009 4:49:38 AM GMT
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.
· 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?
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.
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.
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
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.
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!
·
Kind regards,
Dave
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Dave Andreae
Parallax Tech Support·
Leon
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Amateur radio callsign: G1HSM
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
It's a PDB, the "P" is for "Professional".
Obviously, it's not going to be P for Personal responsibility.
·
Dave
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Dave Andreae
Parallax Tech Support·
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
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
I dont see how it could be much clearer......sorry
regards· john