/diy/ - Do It Yourself

>>1524761
here's the oscillator I used, based on a circuit by Phil Rice VK3BHR, but with a slower comparator (I didn't have the original LM311 on hand)
with SW1 in shown position, an external inductor Lx is connected in series with (and therefore adds to) L2-L4, forming a tank circuit with C6 (a 3300pF 2% film cap I had laying around from another project). U3B provides positive feedback, coupled bidirectionally through C5+C12. U3A is a voltage shifter feeding the oscillations to the micro. the micro counts the frequency using its 16-bit timer and a busy delay loop, then calculates
>L=1/(4*%pi^2*C*f^2)
which is then formatted and printed to the LCD. the Zero button saves the reading and simply subtracts that saved reading from future readings. normally you short the test leads together for a 0-valued Lx then Zero, then connect to the inductor to test
capacitance measurement works similarly, with Cx added in parallel to C6 and the internal inductor, and basically the same math with L and C exchanged, and you leave leads open to zero
>though I'd have to do calculations
computer algebra systems are helpful. e.g. wxMaxima was told that
>f_LC(l,c):=1/(2*%pi*sqrt(l*c));
then told to
>solve(f_LC(L,C) = f,L);
and did so instantly
>saturation tester
hmm intredasting... my main purpose for it is checking hand-wound RF toroids for correct value. once this LC meter achieves its final form (a factory-made proto board and possibly even a box) I'm torn between building a small toroid winder or a scalar network analyzer

>>1524771
that yellow press'n'peel paper works sort of well for me. QFNs are naga happen but SOICs and 0603 (inch) are fine. I sure do miss the solder mask though

>>1524770
parts stocks are built item by item, I've found. ofc you aren't gonna stock shit you don't (yet) know you need. I will say those resistor/capacitor/inductor cut tape assortments on ali are nice and pretty convenient for the impulse build