Bigglez/MrAl's parallel Diode/ series Fuse solution is the most traditional and non invasive (does not modify the current or voltage to the load)protection method.
Just note that the fuse must be rated for a lower current than the diode will blow at and generally lower than the source max current (or it will never blow even with a short) and larger than IDD of the circuit being powered. For protecting an IC based circuit, use a fast blow or instrument fuse.
I have seen situations where the protection diode blows up from overcurrent without blowing any fuse and the IC gets damaged anyway thouogh the fuse would have prevented fire for example but not electrical failure. Even with a properly chosen fuse, there still can be damage from EOS (Electrical OverStress).
If I had a high value chip to protect, I would step up to an onboard regulator. Fortunately this one seems to be reasonably priced.
Your Son might appreciate an adjustable current limited bench power supply at this point. A valuable lesson worth more than the chip I hope has been leanned.
With the heat gun method, you run the risk of moving or stripping the other SMT parts like all those caps. I would just trash the leads and desolder using only an iron, flux and braid (maybe a little added solder to wet the work area) but any of the suggested methds will work with appropriate care. As usual, there is more than one way to do it successfully.
7yr old + battery + developement board = smokebomb
Hi there,
Yes, as hackle says, the fuse has to be appropriately sized,
and the traces or wires leading to it have to be also heavy
enough to withstand the surge current. Traces have been
blown off in the past with a setup like this and im sure you
can find info about that on the web.
As to desoldering the small part, i think what i would do if
nothing else seemed to work is i would take a Dremel drill
with a cut off disk and carefully cut each pin from the
package plastic, separating it from the plastic. The package
itself would eventually come loose where it could be lifted
up, then the pins remaining on the board could be desoldered
one at a time using a standard fine tip iron and desoldering
bulb or even solder wick.
Cutters might not be small enough to cut each pin from the
package body, but with a high speed cutter disk each side
could be done cutting all the pins on one side with one pass.
Of course you have to be very careful not to cut too deep and
damage the board under the package.
Inspect after removing all the pins before soldering a new part.
Repair if necessary before the new part is mounted.
Yes, as hackle says, the fuse has to be appropriately sized,
and the traces or wires leading to it have to be also heavy
enough to withstand the surge current. Traces have been
blown off in the past with a setup like this and im sure you
can find info about that on the web.
As to desoldering the small part, i think what i would do if
nothing else seemed to work is i would take a Dremel drill
with a cut off disk and carefully cut each pin from the
package plastic, separating it from the plastic. The package
itself would eventually come loose where it could be lifted
up, then the pins remaining on the board could be desoldered
one at a time using a standard fine tip iron and desoldering
bulb or even solder wick.
Cutters might not be small enough to cut each pin from the
package body, but with a high speed cutter disk each side
could be done cutting all the pins on one side with one pass.
Of course you have to be very careful not to cut too deep and
damage the board under the package.
Inspect after removing all the pins before soldering a new part.
Repair if necessary before the new part is mounted.
LEDs vs Bulbs, LEDs are winning.
Update...
The heat gun Mfg. was wrong. I tried with a soldering iron and got nowhere fast. That was last week. Today I was fixing a cellphone charger whose cord seemed to fascinate our 6 month old kitten and was finishing up the heat shrinking. I glanced over and saw the board and figured I would try it. After about 30-60 seconds of close heating, mainly in the center of the chip, it pushed right off the pads all at once. Totally unexpected but I am very happy about it.
Kevin
The heat gun Mfg. was wrong. I tried with a soldering iron and got nowhere fast. That was last week. Today I was fixing a cellphone charger whose cord seemed to fascinate our 6 month old kitten and was finishing up the heat shrinking. I glanced over and saw the board and figured I would try it. After about 30-60 seconds of close heating, mainly in the center of the chip, it pushed right off the pads all at once. Totally unexpected but I am very happy about it.
Kevin
Perhaps. The free air may only be 400degF, as quotedpsycho wrote: The heat gun Mfg. was wrong.
but when confined to a target (your IC) the back pressure
slows the air and allows greater heating. Either way it worked!
Great! You can clean up the pads (carefully) withpsycho wrote: After about 30-60 seconds of close heating, mainly in the center of the chip, it pushed right off the pads all at once. Totally unexpected but I am very happy about it.
solderwick. In fact there's prbably enough residual
solder metal to attach the new IC, just add flux.
I'm always scolding myself for over doing the solder
paste on new construction done by hand.
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