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Type: Posts; User: wwfeldman

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1. ## Thread: Converting drill file in um to mm

by wwfeldman
Replies
2
Views
38

### Closed: Re: Converting drill file in um to mm

mm is millimeter, 10^-3 m
um is micrometer, 10^-6 m

converting requires moving decimal point 3 places corresponding to multiplying or dividing by 1000,
depending one which way you're going.
...
2. ## Thread: Stacking diodes for high voltage rectification

by wwfeldman
Replies
13
Views
233

### Closed: Re: Stacking diodes for high voltage rectification

100 uf4007 plus 100 R & C for snubber plus 100 voltage sharing resistor
vs
10 K50UF plus 10 R & C for snubber plus 10 voltage sharing resistors

now compare board space, parts cost, inventory...
3. ## Thread: Will I be able to drive LED with attached analog circuit ?

by wwfeldman
Replies
3
Views
122

### Closed: Re: Will I be able to drive LED with attached analog circuit ?

i think it will work
but the LED is always on, and there are simpler circuits to just turn on the the LED
at 3.5 mA the LED will not be very bright.
4. ## Thread: Stacking diodes for high voltage rectification

by wwfeldman
Replies
13
Views
233

### Closed: Re: stacking diodes for high voltage rectification

Bridge Rectifier won't Rectify

you would need some way to guarantee that all of the diodes carried their share of the voltage

since the uf4007 is rated at 1000 V, 100 of them...
5. ## Thread: Potential Energy and Kinetic Energy of an Electron in an Energy Band diagram

by wwfeldman
Replies
2
Views
234

### Closed: Re: Potential Energy and Kinetic Energy of an Electron in an Energy Band diagram

An attempt:

as you know:
consider the bohr model of hydrogen:
an electron can orbit the nucleus only in specific quantum levels
the lowest level, n = 1, is at -13.6 eV
the next level, n = 2,...
6. ## Thread: damaged remote control

by wwfeldman
Replies
4
Views
165

### Closed: Re: damaged remote control

treat it like a wet cell phone

put it into a container with rice all around for a day or 2 to dry it out
get all of the rice dust off it
then put it back together with a fresh battery.
7. ## Thread: Single conductor inside hollow conductor

by wwfeldman
Replies
25
Views
872

### Closed: Re: Single conductor inside hollow conductor

if anyone wishes to continue he discussion of potential, emf and voltage, etc,
please start a new thread under physics
as this seems somewhat far afield from kajunbee's question
8. ## Thread: Single conductor inside hollow conductor

by wwfeldman
Replies
25
Views
872

### Closed: Re: Single conductor inside hollow conductor

@easy peasy
emf and potential are both measured in volts
when the "voltage" is caused by charges, it is potential and the potential difference between two locations is the voltage we measure
when...
9. ## Thread: Whats the best way to ESD damage a PCB

by wwfeldman
Replies
6
Views
305

### Closed: Re: Whats the best way to ESD damage a PCB

it also depends on the humidity in the air
this time of year, north america, europe etc have relatively high humidity and
static charge does not build up

if you did the carpet shuffle, or the...
10. ## Thread: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transformer

by wwfeldman
Replies
17
Views
733

### Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

this test is accomplished by tieing all of the primary leads together and all of the secondary(ies) leads together
and then applying 3750 VAC

3 mA seems like a lot of leakage
11. ## Thread: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transformer

by wwfeldman
Replies
17
Views
733

### Closed: Re: 1 minute vs 1 second isolation voltage test for isolated offline SMPS transform

the transformer tested for a longer time is likely built better

i expect more critical application require a longer isolation test

what is the 3mA about?
12. ## Thread: Nominal current of diode bridge rectifier

by wwfeldman
Replies
5
Views
271

### Closed: Re: Nominal current of diode bridge rectifier

the data sheet says rectangular pulses, 1/3 of the time, as noted above, 90A output current

conduction by any one diode 1/3 of the time is the most one would expect from a 3 phase sine wave input...
13. ## Thread: 12 vdc led running very hot

by wwfeldman
Replies
12
Views
373

### [SOLVED]Closed: Re: 12 vdc led running very hot

please provide the circuit the LEDs are in, the part number of the LED
and any known voltages or currents
14. ## Thread: Isolate R37 from Equation

by wwfeldman
Replies
2
Views
183

### Closed: Re: Isolate R37 from Equation

try this:
apply voltage divider at the + input of the op amp V+ = ...

assuming a perfect op amp, V- and output = V+

combine R25 and R28 to one equivalent resistor

assuming Vo is open,...
15. ## Thread: Drive motor through IRF520 MOSFET module and Arduino

by wwfeldman
Replies
1
Views
121

### Closed: Re: Drive motor through IRF520 MOSFET module and Arduino

please draw the circuit for the arduino, the MOSFET Drive Module and the motor
show the connections between the arduino the mosfet driver and from the mosfet driver to the motor
show all voltage...
16. ## Thread: How to use the same RELAY on 12V & 24V vehicles

by wwfeldman
Replies
10
Views
367

### Closed: Re: How to use the same RELAY on 12V & 24V vehicles

what load does the relay handle? V? I? etc

Kyotto makes a series of solid state relays with a control voltage range of 4 to 32 V

load voltage ranges 24 to 280 VAC and currents 10, 15, 25, 40,...
17. ## Thread: Single conductor inside hollow conductor

by wwfeldman
Replies
25
Views
872

### Closed: Re: Single conductor inside hollow conductor

@easy peasy:
potential (voltage) is the energy per unit charge based on static charge distributions
things where we use V = sum of kq/r or integral thereof for continuous charge distributions
...
18. ## Thread: HP 54520A Blown Fuse Problem

by wwfeldman
Replies
28
Views
1,100

### Closed: Re: HP 54520A Blown Fuse Problem

suggestion:
find an identical 'scope on ebay or a used equipment place
get it for spare parts
if it turns on, but the 'scope doesn't work, you have a new power stage

useless suggestion:
when...
19. ## Thread: Single conductor inside hollow conductor

by wwfeldman
Replies
25
Views
872

### Closed: Re: Single conductor inside hollow conductor

the outer conductor of coax is usually stranded and woven
if it was solid, like a pipe, it wouldn't bend.

when i asked where the return path was, i did assume a current
as you know, there is...
20. ## Thread: Single conductor inside hollow conductor

by wwfeldman
Replies
25
Views
872

### Closed: Re: Single conductor inside hollow conductor

yes
where is the return path of the AC current?
21. ## Thread: OP07 circuit output voltage?

by wwfeldman
Replies
24
Views
732

### Closed: Re: OP07 circuit output voltage?

this question appeared in this thread
13.9 V instead of 2.75 v, Which parts are failing?

so my question is what are umsch1 and umsch2 connected to?
umsch1 is directly connected to the...
22. ## Thread: What dc can u measure?

by wwfeldman
Replies
5
Views
416

### Closed: Re: What dc can u measure?

assuming sinusoidal waves, and since there is no apparent load, all three circuits act as peak detectors.

If Veff is Vrms, then Vpeak = sqrt(2) * Veff or Vpeak = sqrt(2) * 20,5 V = 28.99 V
...
23. ## Thread: 230V AC to 5V DC push button interfacing

by wwfeldman
Replies
9
Views
381

### Closed: Re: 230V AC to 5V DC push button interfacing

why are you changing the switch from a nice, safe, working 5V switch and circuit
to an untested, not so safe 230V switch and circuit?

How are you changing the voltage/power to the fan to...
24. ## Thread: H-Bridge Inverter breaks after a while

by wwfeldman
Replies
10
Views
436

### Closed: Re: H-Bridge Inverter breaks after a while

What is connected to the output, P0 and P1?

what is the capacitance of C400V Power Cap?

how much current is in that 680 nH inductor feeding the bridge rectifier?

I built a switch mode...
25. ## Thread: 13.9 V instead of 2.75 v, Which parts are failing?

by wwfeldman
Replies
3
Views
313

### Closed: Re: 13.9 V instead of 2.75 v, Which parts are failing?

your schematic is very hard to read

what is N403?
what does the red line below and to right of red "?" connect to?

without information about parts and what you are expecting it to do,
it...
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