<sb0>
whitequark, I suspect some are still around :)
<whitequark>
but I can say for a fact that *no* precious metals have survived for more than like
<whitequark>
ten minutes after the fall of ussr
<sb0>
I know a fab near Warsaw that still uses a lot of USSR-era equipment
<sb0>
including large oil diffusion pumps etc.
<sb0>
maybe mercury, even :)
<whitequark>
mmm, pumps
<whitequark>
mercury isn't really precious
<sb0>
(it's been on my todo-list for a while, but I'm never in Poland at the right time)
<sb0>
and I don't mean for the precious metals, just for the vacuum/electronic porn
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<whitequark>
what's a good way to make a constant-current regulator for 1A?
<whitequark>
lm317?
<whitequark>
hm, no, that'd dissipate at least 3W
<ysionneau>
STCS1A ?
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<whitequark>
ysionneau: oh great
<whitequark>
ysionneau: oh actually not, I can't find anywhere to buy it in RU
<whitequark>
not even "not in stock"
<whitequark>
though nevermind, I just realized I have digikey covered
<whitequark>
and DK has it in stock
<sb0>
what do you need this regulator for?
<sb0>
just curious
<whitequark>
sb0: I have 24V input and I want to power a water (coolant) pump for my CNC mill
<whitequark>
at about 1A it works best
<sb0>
constant voltage isn't good?
<whitequark>
I dunno actually
<whitequark>
they're probably more or less equivalent
<whitequark>
in this case
<sb0>
and what happens at max voltage?
<whitequark>
you mean at 24V?
<sb0>
the problem with driving a DC motor with constant current is that if you reduce the load (torque), the voltage and speed will go up
<sb0>
yes
<whitequark>
oh
<whitequark>
oh you're right.
<sb0>
if you run out of water, won't it make the motor spin too fast?
<whitequark>
I need constant voltage here
<whitequark>
it will, and it'll burn
<wpwrak>
that should be easy to fix. even an arduino could do that ;-)
<sb0>
the problem with pure constant voltage is the current spike at startup, when the motor isn't already spinning
<sb0>
but in some cases, the circuit's resistance is enough to keep that current within a reasonable value
<sb0>
of course, if you block the motor then, the current will stay high
<wpwrak>
so have a controller. monitor voltage. on start, allow for inrush current. then limit voltage (probably needs a low-pass filter). if it gets too high, uncommanded, emergency shutdown.
<wpwrak>
and yes, maybe also if the voltage gets too low :)
<sb0>
motors are inductive too, which helps limit the inrush current
<sb0>
so in a lot of cases, constant-voltage is the best simple solution :)
<sb0>
you can also add a slow-acting fuse ...
<wpwrak>
i guess you want to control both - current and voltage. regulate one, monitor the other. then you can detect any problems and just cut off. at least that's the theory :)
<whitequark>
so contrived
<wpwrak>
in russia, it's normal for motors to burn
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<DocScrutinizer05>
use a constant voltage with current limiting, and possibly even softstart. All available in very common cheap and simple regulator chips
<DocScrutinizer05>
usually with 3 pins
<DocScrutinizer05>
maybe for this usecase you prefer a 5pin version, that allows separate control for current limit and softstart
<DocScrutinizer05>
the 3 pin versions do no softstart and current limit is usually "hardcoded" and foldback characteristics which you don't really want
<DocScrutinizer05>
but actually you might get away with very convenient PWM on 50%, which doesn't even need any heatsink
<DocScrutinizer05>
since the motor is inductive, you only need a oscillator driving a power mosfet, and a clamp diode