^ no
(Caffeine deprivation effect)
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
perforated channel, when it actually connects low-impedance source to drain.
Nah, the line is the cathode connected edgewise.
Cheers
Phil Hobbs
The fuse should be before the switch.
Ok... It finally dawned on me what the error in the circuit is. I was bit by this very error many years ago when I built a simple power supply using the LM7805 and a couple LM317 regulators.
And the answer is: The LM7805 requires a minimum load of 5ma to maintain regulation. There is no resistor on the LM7805 to provide the 5ma load current. Connect a
1K resistor from the LM7805 output to ground and it will regulate properly.Cheers, Dave M
I think it's the 317 and its ilk that need a minimum output current, because they push the quiescent current out there in order to minimize the adjust pin current. The 78xx parts push the quiescent current out the ground pin.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
There is no minimum output current on the 7805, though the regulation etc. is specified with a non-zero output current. We used many thousands with < 1mA load (and no output capacitor) with no problems.
Yes but only assuming it is a stand alone supply. Sure, you wouldn't want that volttagee too high with the output cap charged and then connect it to your DUT.
However they are not likely to have that problem when in a wired in a circuit.
In other words you're right, but conditionally.
No, he's not right.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reminds me of the line "Parts is parts..."
"A charged cap is a charged cap is a charged cap..."
They will "unload" or "dump" their stored charge into whatever load you present them with in accordance with Ohm's law until empty.
So, it is usually considered a bad thing to apply your PS leads to your DUT energized already. One usually applies non-energized lines to the DUT power input pins, and THEN energizes the supply via manual switch throw or electronic means.
Any properly designed supply which has some form of capacitor based storage or output 'filtration' on it, typically also has a bleeder resistor on said cap bank or even each cap, which will drain them when not in actual use.
If there is an exception, it would be supplies filling supercaps or batteries, but then those get the "UPS" moniker, not "power supply".
Dunno if anyone posted circuitcellar's answer, but if you haven't seen it:
-- Silvar Beitel
Who says they're right ? OK, I can understand their answer but at very light loads it would work fine.
But they say it's OK to put the switch before the fuse ?
Really, 470uf with out specifying a secondary voltage or load current?
Cheers
Or frequency?
Without specifications, their answer makes no sense.
People who can design electronics, do. People who can't design electronics run web sites and publish magazines.
Really.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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