Blown OEM BS2
Bill Chennault
Posts: 1,198
All--
My robot uses four OEM BS2s. Tonight, I think I "blew" two of them. I have three more coming this way, as a result.
This is what I did . . . a stupido because I was tired: I "reset" the entire five Stamp system (a BS2p40 module, and four OEM BS2s) by removing power and reapplying power via a simple jumper wire unplug/plug operation. Well, this time I plugged the Vin wire right into ground. Ha! The Vin wire in my hand got hot! (However, I do not know how this could affect the Stamps. In my thoughts, it is just a direct short which does not involve the Stamps.)
And, only TWO of the OEM BS2s·died. The other two, using the same power in the same breadboard still work fine, as does the BS2p40 module. My question is, What might have happened to them? Did I blow the LM2904? Or, is it likely that I did something else? I would like to try to fix them, not because of the money, but because I want to learn a little.
Any suggestions?
Thanks!
--Bill
ps NOW, I am going to rig a pushbutton up for reset purposes!
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You are what you write.
My robot uses four OEM BS2s. Tonight, I think I "blew" two of them. I have three more coming this way, as a result.
This is what I did . . . a stupido because I was tired: I "reset" the entire five Stamp system (a BS2p40 module, and four OEM BS2s) by removing power and reapplying power via a simple jumper wire unplug/plug operation. Well, this time I plugged the Vin wire right into ground. Ha! The Vin wire in my hand got hot! (However, I do not know how this could affect the Stamps. In my thoughts, it is just a direct short which does not involve the Stamps.)
And, only TWO of the OEM BS2s·died. The other two, using the same power in the same breadboard still work fine, as does the BS2p40 module. My question is, What might have happened to them? Did I blow the LM2904? Or, is it likely that I did something else? I would like to try to fix them, not because of the money, but because I want to learn a little.
Any suggestions?
Thanks!
--Bill
ps NOW, I am going to rig a pushbutton up for reset purposes!
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You are what you write.
Comments
One almost guaranteed way to destroy this hardware is to put ground on Vin and Vin on ground. Reversing the voltages in this way is quite destructive.
Maybe you damaged the power source ?
try them one at a time to make sure its not a power issue.
Without knowing exactly how the wiring is run, cant say for sure, but seems like it wouldnt have hurt the stamps.
I agree with both of you: What I described should not have affected anything . . . other than perhaps my thumb and forefinger! So, let me describe it differently . . .
I had a power issue. There was a spark and Vin got hot. I don't know what happened other than two of my OEM BS2's--out of the string of identically wired four--are for all intents and purposes, DEAD. The IDE will not "Identify" them and the if I try to run a program, I get the Stamp not found message. (Gee. How many times have we read that on this forum?)
I have tried them all by themselves and received the same results. I am sure they are toast. But, are they like charred toast, or perhaps with a little TLC I can fix them? I could easily replace an LM2904 and its cap. I could buy another PIC chip, etc.
I suppose I should start with a voltmeter and see if I can find +5vdc coming out of the LM2904? (It is not the money; I want the experience of fixing them.)
Thanks!
--Bill
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You are what you write.
The voltmeter tells me one (blown) OEM BS2 has +6.86vdc on VDD and the other (blown) OEM BS2 has 0.00vdc on VDD. (My two good ones both read +4.98vdc on VDD.)
Does this tell any of you anything other than both have the wrong voltage? It LEADS me to think that the common denominator is the LM2904. But, I have too little electronics knowledge and can be easily led.
Thanks!
--Bill
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You are what you write.
The OEM BS2s are all fine. When I shorted out the breadboard power (7.2vdc at 8400maH), I simply destroyed a big part of it.
--Bill
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You are what you write.
This time, the damage was not visible. I just started looking at continuity. I found it "here" but not "there" so I knew between those two points lie the problem. This big breadboard has a pair of power busses running around all four sides and up and down in the middle in ? (I forgot) how many places. I just tossed the bad power bus in the trash and put everything back together.
Works fine.
--Bill
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You are what you write.
I got to thinking about the fact that I could not see the damage. So, I dug the ruined piece out of the trash and peeled the insulating, sticky backing off and took a look through the microscope. Here is what I found (you were PRECISELY correct) . . .
On the left is the intact "fuse" in the other rail. The rail on the right was only blown at the location above, however, there were three more locations that had heated to the point that they melted either the sticky backing or·breadboard plastic in which they were embedded.
--Bill
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You are what you write.
Hopefully, there will be no more! I am going to put a switch in Ugly Buster's logic supply·to prevent this from happening again.
Ha! A direct short in a 7.2vdc, 8.4 amp hour·circuit is NOTHING compared to one in the 12vdc, 24 amp hour circuit! That is why the latter is now controlled by a Stamp using a Futurlec solid state relay. (Thanks, Mike G.)
--Bill
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You are what you write.
Post Edited (Bill Chennault) : 12/6/2007 10:26:22 PM GMT
On the "blown" boards, have you tried running a regulated 5v to the VDD, and bypassing the regulator? Might give you more info.
David
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David
There are 10 types of people in this world,...
Those that understand binary numbers, and those that don't!!!
Thank you for thinking about this for me!
As it turns out, there was absolutely nothing wrong with OEM BS2 boards . . . it was more my inexperience.
allanlane5 figured out what it had to be and it was; it just took me a while to verify it. Take a look at the microscopic picture above.
--Bill
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You are what you write.