Re: Flying Diodes and Tongue in Cheek
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Hi Chuck. Sorry about your casualty. I guess those diodes also make a good fuse :-) I think an 0805 package LED would fit, but I don't think it's a good idea. The full current supply will flow through that device (30mA or so) which would probably toast most SMD LEDs. If you found an LED that could handle that forward current, the forward voltage would be much higher than the schottky diode, which would impact the minimum supply voltage. Plus, it would be insanely bright and would probably get quite warm. I'm looking forward to your videos! 73 Mike M.? KU4QO
On Thu, Mar 27, 2025 at 3:13?PM chuck adams via <chuck.adams.phd= [email protected]> wrote: Gang,
1.? I was joking the other day about the SMD build of the uni-VFO and how I
set the world record for a flying diode.? And I said I didn't need a diode.
The village idiot strikes again.? I bought 3 of the VFOs to experiment with.
For the purpose of learning soldering and for multiple projects I thought of
for using them.
Late last night or early this a.m., I'm up past my bedtime and on the
workbench
with the second VFO.? It was working nicely.? I made the mistake of
finding a
way to short the 3.3V to ground.? I was wondering why the critter quit
working.
With a 20x loupe I saw that the diode had this nice little shiny bump
dead center
of the top.? DVM verified that I had blown it.? Shorted out the
connection, but
externally I put a schottky diode externally for now.
Mike et al, please put an LED in its place.? It protects and serves as a
power
indicator.? IMHO.? Is there an LED that size?
2.? Tongue in cheek.? The other day I said that I didn't need to know ahead
time how much space a circuit was going to need.? Attached.? Page from the
lab book of the schematic and a page showing the hand drawn layout.? I have
written, a long time ago, a computer program to do this and it's description
is in one of my docs that were/are online somewhere.? I caught someone with
that one.
Note.? Crystal in wrong place on both pages.? I had that corrected when
soldering as I recognized the error.? Nice to have the Colpitts circuit
memorized after many years of using it.? Also, in layout, the two caps
were missing, but again I'm using both pages as I build to double double
check.? It does help catch a lot of errors when you are rushed.
FYI
chuck, aa7fo
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