I can't be trusted with a soldering iron

A project log for REMB - Raz0r Electric Mountain Board

An electric mountain board, built from scooter parts.

Daren SchwenkeDaren Schwenke 09/03/2019 at 07:222 Comments

After a fun day with the family, this evening I went about replacing the under-rated transistors I had driving my braking mosfets with some BC337 ones.  They have a more respectable 50v CE voltage rating and should work well.

I was offline and never bothered to check the datasheet for them.  It's an NPN BJT transistor.. how hard can this be.

Cue the smell of atomized silicon and motors spinning out of control.

<insert expletives here>

Stupidly try the other channel...

<insert more expletives here>

Later, go read the actual datasheet.  The 2N3904 has an EBC pinout.  The BC337 has a CBE pinout.  I built it with my transistors wired in backwards.

<insert even more expletives here>

I've now blown more power mosfets in the last week than I have in at least the last 5 years and I do terrible things with them.  Then again, I usually don't just 'wing it' when the power involved could easily vaporize my wiring.

The main problem here is a combination of arrogance, the complete lack of much of my equipment, and the tiny form factor I've forced myself into.  Keeping with my goal of fitting everything within the board cross section, the power section needs to fit in a rectangular cube 3/4x3/4x3in including connectors and the minimum space I need for the mosfets consumes most of that.  So.. bench testing has been pretty much non-existent.

It works on paper.  It physically fits.  I just need to stop screwing up now.

I'll be rebuilding the power section again tomorrow.  Good thing I keep a bin full of power mosfets and transistors around..


Ken Yap wrote 09/03/2019 at 13:41 point

I can't be trusted with chips. Back when I was an intern, I inserted all the 2112 dynamic RAMs on a PDP-11/23 expansion board the wrong way. Boy were they hot. Boss wasn't happy, but didn't hold a grudge. Ribbed me now and then about my boo-boo. Now I always look carefully for the notch or the pin 1 dot. Not just for the chip's sake but also the rest of the circuit I may have to redo.

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Dr. Cockroach wrote 09/03/2019 at 11:42 point

Bummer, I did the same thing back when working with the Cardboard Computer. I was using 2n2222's and A friend sent me a large amount of BC549's. I did not look into the Emitters and Collectors being reversed and blew a few of them myself. The smell was wonderful.... Not ;-)

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