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AC/DCdude17
Guest

Wed Sep 29, 2004 4:25 pm   



X-No-Archive: Yes



Quote:


If you have a little search on the web, you will see hat PF is defined
in a more general way than by simple phase angle, which as noted, is
meaningless for non-linear loads.


It's simple. The universal definition of power factor is the quotient of
real power in watts over apparent power in VA.

The average power factor is calculated by dividing VAh by kWh

AC/DCdude17
Guest

Wed Sep 29, 2004 4:25 pm   



X-No-Archive: Yes

You need to feed them with 288V(240 x 6/5 to compensate for frequency)
60Hz.



goldencap wrote:

Quote:
In Rio de Janeiro the electrical standard is 127V between fase and
neutral,
220V between fases, and the frequency all over Brazil is 60Hz..
I need to be able to use British standard fluorescent batons, and a
neon sign that usually runs at 240v 50HZ
How can I manage this ?????

Thanks A


ChadMan
Guest

Wed Sep 29, 2004 4:25 pm   



one of the best places to start, because it helps you ask more questions
and seek more answers is by going to radio shack and getting their new
book "Getting started in electronics" that encompasses all of their old
Forest Mimms mini engineers notebooks. They have lot's of cool little
projects and off some good beginning info. Radio shack will also be a
source for some entry level components like 1/4 watt and 1/2 watt resistor
assortments, electrolytic capacitor assortments disc capacitor assortments
and LEDs and what not. I like to build things like small projects and try
to find out how they work along the way. Get a breadboard or two also.

As for the previous fellow with the hammer analogy, I worked with a hammer
for 20+ years, now because of a start like the one I described above I am
the Webmaster, Network Admin. and advertising graphics artist for our
company.
I write all of our instructions and do all of our technical illustrations,
manage our product labeling system and they are paying for my electronics
education (CIE course while I work), I am starting to teaching myself to
write assembly for PIC microcontrollers (which most of our products use).
At this time I have put all aside for our second in house video (I am the
technical editor) on a video editing system that I built. It is an
instructional
video for all of our testers.

So I say grab on and have fun, keep asking questions and don't feel like
any question is a stupid question.

ChadMan
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chad for Dinosaur Electronics
See our website at:
http://DinosaurElectronics.com
For tech help call us at:
(541) 994-4344 8-5 M-F PST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---

"Chris" <imustberich7_at_wmconnect.com> wrote in message
news:122c716d.0306301624.7a4b5cb3_at_posting.google.com...
Quote:
I am a beginner in basic electronics. I've just done my first 555
timer project with electrnics learning lab. I couldn't understand very
well how the 555 timer worked. I have just followed the book to put
the 555 timer project together. I am also looking for a freeware
professional electronics calculator to download online that can
calcuate from ohm's law all the way down to binary numbers. I also
need to find out as much info about the 555 timer as possible.


ChadMan
Guest

Wed Sep 29, 2004 4:25 pm   



Quote:

"Chris" <imustberich7_at_wmconnect.com> wrote in message
news:122c716d.0306301624.7a4b5cb3_at_posting.google.com...
snipped
I am also looking for a freeware
professional electronics calculator to download online that can
calcuate from ohm's law all the way down to binary numbers. I also
need to find out as much info about the 555 timer as possible.



ESB Calc is one of the best calculators I have found.
Ohm's law is best kept in your head!!! Start by using
one of the charts that are on the web:
http://members.tripod.com/~schematics/ohmslaw.htm

Windows scientific calculator will do hex, bin conversions
just fine.
Best scientific calculator here ESB Calc here:
http://www.esbconsult.com.au/esbcalc/esbcalc.html


ChadMan

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chad for Dinosaur Electronics
See our website at:
http://DinosaurElectronics.com
For tech help call us at:
(541) 994-4344 8-5 M-F PST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---

AC/DCdude17
Guest

Wed Sep 29, 2004 4:25 pm   



X-No-Archive: Yes

"Benoit F." wrote:

Quote:
Hi,

I am building a power supply for my Matrix Orbital LCD. I am using a 7805
voltage (+5V) regulator with a 100uF capasitor before and after the chip. I
have seen lots of differents design of this PSU and i just don't know which
one is the best. Could someone help me with this, i just want to be sure i'm
doing the right thing before i blow off my 100$ LCD unit.

I also have some question about the 7805 voltage regulator...

1. How the chip will react if it is overheated?

2. What is the minimum input voltage that must be applied to run effectively
the 7805 chip?

Depends on the type of 7805 you get. Low drop version can operate on 6V.

I'd give it about 8V.

Remember, Vin-Vout x current = dissipation from 7805 and you should not hover
too close to their rated maximum dissipation, which is rated using an infinite
heatsink.

How many amps does your LCD unit draw?

If it's less than 1A, I recommend an Iomega Zip drive AC adaptor. Most AC
adaptors are not regulated and they're often about 50% over their rated voltage
under no load, but the Iomega AC adapter is internally regulated to 5.0 to 5.1V
with a 7805 like device.

You should be able to find one for $10 to 15 including shipping on eBay. It may
or may not be more expensive than building your own, but you will have
everything nicely self contained inside the wallwart block.

Henry Kolesnik
Guest

Wed Sep 29, 2004 4:25 pm   



If you've received a private reply please share it as I also recall the test
you've mentioned.
tnx
hank wd5jfr
<scottatlgh_at_despammed.com> wrote in message
news:3e03c610.0306260931.6a6d0b93_at_posting.google.com...
Quote:
About twenty-five years ago a colleague showed me how to do a ring
test on a power transformer. I need to test a SMPS transformer now and
I can't remember how he did this test. I know he used an oscilloscope
to look at the ringing but that's as far as my memory serves me. A
website on the internet explained some kind of a ring test but it
didn't give me the output I was expecting. Can someone please point me
in the right direction.

Thanks,

Scott


G.T.W.
Guest

Wed Sep 29, 2004 4:25 pm   



A debounce circuit?

On Thu, 19 Jun 2003 20:14:44 +0100, Terry Pinnell
<terrypinDELETE_at_dial.pipexTHIS.com> wrote:

Quote:
Can anyone come up with a simple, (R/C/diode) circuit that will
reliably produce a +ve spike of say 100 ms when it is first opened
please?

In theory I thought the configuration below should work. But, with
fairly noisy switches, I get some +ve spikes when the switch is
*closed* again. (I'm feeding this to an NPN BJT and taking an output
from its collector, and getting unwanted brief -ve going spikes.)

As a second best, I'll settle for R/C/diode/transistor.




+12V
o------o----o
|
.-.
| |
| |
'-' || Out
|--------o-||o----o------o----o
o || | |
\ | -
NC switch \ .-. ^
o \ | | |
(not button) | | | |
| '-' |
| | |
| | |
| | |
| | |
| | |
=== === ===
GND GND GND

--
Terry Pinnell
Hobbyist, West Sussex, UK



Ratch
Guest

Wed Sep 29, 2004 4:25 pm   



Look at this site http://sencore.com/ and click on products until you
find the HA325 Horizontal Output & Flyback Tester. You can down load the
manual for this instrument which does a ringing test on the coils. Hope
this helps a little. Ratch


<scottatlgh_at_despammed.com> wrote in message
news:3e03c610.0306260931.6a6d0b93_at_posting.google.com...
Quote:
About twenty-five years ago a colleague showed me how to do a ring
test on a power transformer. I need to test a SMPS transformer now and
I can't remember how he did this test. I know he used an oscilloscope
to look at the ringing but that's as far as my memory serves me. A
website on the internet explained some kind of a ring test but it
didn't give me the output I was expecting. Can someone please point me
in the right direction.

Thanks,

Scott


Henry Kolesnik
Guest

Wed Sep 29, 2004 4:25 pm   



Back in the mid 1950s when I was in high school I worked in a Radio& TV shop
and we had a small box called a Flyback and Yoke Tester that could find one
shorted turn in no time. I don't recall the manufacturer but it was real
simple and this is the crcuit that I think I'm recalling. I'm downloading
the HB325 manual as I write. It was kind of hard to find so here is the
URL:
http://www.sencore.com/products/ha325/HA325Manual.pdf

tnx
hank wd5jfr
ps if anyone recalls the simple one I used in the 50s please drop me an
email.

"Ratch" <rohland.atchison_at_comcast.net> wrote in message
news:u24Na.30504$926.2980_at_sccrnsc03...
Quote:
Look at this site http://sencore.com/ and click on products until you
find the HA325 Horizontal Output & Flyback Tester. You can down load the
manual for this instrument which does a ringing test on the coils. Hope
this helps a little. Ratch


scottatlgh_at_despammed.com> wrote in message
news:3e03c610.0306260931.6a6d0b93_at_posting.google.com...
About twenty-five years ago a colleague showed me how to do a ring
test on a power transformer. I need to test a SMPS transformer now and
I can't remember how he did this test. I know he used an oscilloscope
to look at the ringing but that's as far as my memory serves me. A
website on the internet explained some kind of a ring test but it
didn't give me the output I was expecting. Can someone please point me
in the right direction.

Thanks,

Scott



Robert McCormick
Guest

Wed Sep 29, 2004 4:25 pm   



TI has an app note on the MSP430 that gives you a range of ideas on how to
solve that problem. Not sure what the doc number was but it is on the app
notes page.

Also, Maxim has a number of great parts that can do unidirectional and
bidirectional level shifting between to voltage levels. Last one I looked
at would go as low as 1.2V and as high as 5.5V.


"Ole Voss" <ole.voss_at_netrogue.de> wrote in message
news:bcvsvg$o0oae$1_at_ID-118921.news.dfncis.de...
Quote:
I'm using the TI MSP430 mictrocontroller and was wondering how it is
basically possible to interface 5V peripherals to a 3.3V microcontroller.
Could somebody give me a hint what to do?


Thanks a lot!

Ole.



Kevin Dressel
Guest

Wed Sep 29, 2004 4:25 pm   



All:

Based on the feedback I received from you guys (thanks for that!) and after
referencing a few web pages, I created the following circuit (mind you I've
got two of these paralleled across the cap for 10 LEDs total):



470ohm 5 LEDs in series (Specs show 3.6V drop
@ 20mA)
(+)---------+----/\/\/----|>|-|>|-|>|-|>|-|>|--+
| 1/2W 18V Drop |
| |
Transformer 1000U | |
Vin = 10.5V 50V ----- Filter Cap reads |
w/ no load ----- 27-28V w/ no load |
| |
| |
| |
(-) -----------+-------------------------------+

Now, assuming I understood everything correctly up to this point, I should
be getting approx. 21mA current in the LEDs (28V-18V = 10V / 470ohm ~=
21mA), right? So, why is it then that when I check the current across the
LEDs with the multimeter, I read around 42mA (around 22mA across one LED)?

Also, when I light these LEDs up with a 3.6volt power source (three nicad
batteries), they are much brighter than when used in the circuit shown
above. Does anyone know why this would be?

Am I missing a crucial piece of the puzzle here?

Thanks,
Kevin

Kevin Dressel wrote:

Quote:
All:

I am trying to light up 10 white LEDs using an AC/DC transformer.
Originally, this transformer was used to charge batteries. The input is
120volt/60Hz/8watts (US) and the output is supposed to be 15volt
DC/100mA. I would like to wire 4 of the LEDs (3.6 volt drop across each
one, 20mA) in series with a 47ohm resistor (just to be safe with the
LEDs). This should give me slightly less light output at 15 volts due
to the reduced current.

Now for the question:

Based on readings from my multimeter, the output sits right around 10.5
volts. However, in experimenting with the adapter, I have been able to
put 5 LEDs in series with the 47 ohm resistor with no visible loss of
light (versus not having the resistor there - Quick note: I was able to
see a drop in light output upon putting a 220ohm resistor in series with
the LEDs). Why am I able to drive 5 LEDs when the volt meter is reading
only 10.5 volts DC? What's wrong with this? 5*3.6volts=18volts + 47ohm
* .02A = 18.94 volts? This is way more than 10volts! Is this due the
to fact that this adapter was used for charging batteries? Should I
maybe put a 12volt DC voltage regulator in the circuit?

I'm pretty confused...

Thanks for any help!

Regards,
Kevin


John G
Guest

Wed Sep 29, 2004 4:25 pm   



You say you checked the current ACCROSS one led and it is 22ma and ACROSS
the lot it is 42ma.
That's about expected results but very wrong practice.
Yo must measure current in SERIES with the load not ACCROSS it.
When you measured across one led you more or less removed that led from the
circuit and measured the current thru the rest.
When you measured across all the leds you more or less removed them from the
circuit and measured the current thru just the resistor and 42ma multiplied
by 470 Ohms gives about 19.7 volts which is about right for the supply volts
you quote.
If you had measured the current across the lot including the resistor the
current would have only been limited by the powersupply or the meter
selfdestructing whichever was the weaker.
--
Wot's Your Real Problem?
John G.


"Kevin Dressel" <dressel1_at_charter.net> wrote in message
news:3F06264D.4BB9FCE5_at_charter.net...
Quote:
All:

Based on the feedback I received from you guys (thanks for that!) and
after
referencing a few web pages, I created the following circuit (mind you
I've
got two of these paralleled across the cap for 10 LEDs total):



470ohm 5 LEDs in series (Specs show 3.6V
drop
@ 20mA)
(+)---------+----/\/\/----|>|-|>|-|>|-|>|-|>|--+
| 1/2W 18V Drop |
| |
Transformer 1000U | |
Vin = 10.5V 50V ----- Filter Cap reads |
w/ no load ----- 27-28V w/ no load |
| |
| |
| |
(-) -----------+-------------------------------+

Now, assuming I understood everything correctly up to this point, I should
be getting approx. 21mA current in the LEDs (28V-18V = 10V / 470ohm ~=
21mA), right? So, why is it then that when I check the current across the
LEDs with the multimeter, I read around 42mA (around 22mA across one LED)?

Also, when I light these LEDs up with a 3.6volt power source (three nicad
batteries), they are much brighter than when used in the circuit shown
above. Does anyone know why this would be?

Am I missing a crucial piece of the puzzle here?

Thanks,
Kevin


Kevin Dressel
Guest

Wed Sep 29, 2004 4:25 pm   



Thanks for the reply. That explains the differences between the two readings.
I rechecked it and got about 19mA through the entire circuit. I figure that
based on this, I could brighten things up a bit by reducing the resistor to
around 430 ohms, which should take the current up to around 20mA.

Regards,
Kevin

John G wrote:

Quote:
You say you checked the current ACCROSS one led and it is 22ma and ACROSS
the lot it is 42ma.
That's about expected results but very wrong practice.
Yo must measure current in SERIES with the load not ACCROSS it.
When you measured across one led you more or less removed that led from the
circuit and measured the current thru the rest.
When you measured across all the leds you more or less removed them from the
circuit and measured the current thru just the resistor and 42ma multiplied
by 470 Ohms gives about 19.7 volts which is about right for the supply volts
you quote.
If you had measured the current across the lot including the resistor the
current would have only been limited by the powersupply or the meter
selfdestructing whichever was the weaker.
--
Wot's Your Real Problem?
John G.

"Kevin Dressel" <dressel1_at_charter.net> wrote in message
news:3F06264D.4BB9FCE5_at_charter.net...
All:

Based on the feedback I received from you guys (thanks for that!) and
after
referencing a few web pages, I created the following circuit (mind you
I've
got two of these paralleled across the cap for 10 LEDs total):



470ohm 5 LEDs in series (Specs show 3.6V
drop
@ 20mA)
(+)---------+----/\/\/----|>|-|>|-|>|-|>|-|>|--+
| 1/2W 18V Drop |
| |
Transformer 1000U | |
Vin = 10.5V 50V ----- Filter Cap reads |
w/ no load ----- 27-28V w/ no load |
| |
| |
| |
(-) -----------+-------------------------------+

Now, assuming I understood everything correctly up to this point, I should
be getting approx. 21mA current in the LEDs (28V-18V = 10V / 470ohm ~=
21mA), right? So, why is it then that when I check the current across the
LEDs with the multimeter, I read around 42mA (around 22mA across one LED)?

Also, when I light these LEDs up with a 3.6volt power source (three nicad
batteries), they are much brighter than when used in the circuit shown
above. Does anyone know why this would be?

Am I missing a crucial piece of the puzzle here?

Thanks,
Kevin


Watson A.Name - 'Watt Sun
Guest

Wed Sep 29, 2004 4:25 pm   



In article <3F06264D.4BB9FCE5_at_charter.net>, dressel1_at_charter.net
mentioned...
Quote:
All:

Based on the feedback I received from you guys (thanks for that!) and after
referencing a few web pages, I created the following circuit (mind you I've
got two of these paralleled across the cap for 10 LEDs total):



470ohm 5 LEDs in series (Specs show 3.6V drop
@ 20mA)
(+)---------+----/\/\/----|>|-|>|-|>|-|>|-|>|--+
| 1/2W 18V Drop |
| |
Transformer 1000U | |
Vin = 10.5V 50V ----- Filter Cap reads |
w/ no load ----- 27-28V w/ no load |
| |
| |
| |
(-) -----------+-------------------------------+

Now, assuming I understood everything correctly up to this point, I should
be getting approx. 21mA current in the LEDs (28V-18V = 10V / 470ohm ~=
21mA), right? So, why is it then that when I check the current across the
LEDs with the multimeter, I read around 42mA (around 22mA across one LED)?

Also, when I light these LEDs up with a 3.6volt power source (three nicad
batteries), they are much brighter than when used in the circuit shown
above. Does anyone know why this would be?

Am I missing a crucial piece of the puzzle here?

You cannot measure across the LEDs with the DMM on the current range,
because it's almost a dead short. You must measure the current by
inserting the DMM between the resistor and LEDs, in other words in
series.

If you put the LED across the 3.6V, you should *still* put a current
limiting resistor in series with it. If you don't, then the battery
is probably pushing much more than the 30 mA maximum thru the LED.
Watch out for the overly hot LED.

Quote:
Thanks,
Kevin

[snip]

--
@@F_at_r_at_o_at_m@@O_at_r_at_a_at_n_at_g_at_e@@C_at_o_at_u_at_n_at_t_at_y@,@@C_at_a_at_l@,@@w_at_h_at_e_at_r_at_e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t_at_h_at_e@@a_at_f_at_f_at_l_at_u_at_e_at_n_at_t@@m_at_e_at_e_at_t@@t_at_h_at_e@@E_at_f_at_f_at_l_at_u_at_e_at_n_at_t@@

Kevin Dressel
Guest

Wed Sep 29, 2004 4:25 pm   



I figured that was the reason. I did put a 10 ohm resistor in series with the
3.6v source and the LED, but it still appeared brighter (of course, that is based
on my eyes, which are far from perfect).

For the series of 5, I figure I can get by with a 430ohm resistor (maybe a 390ohm
if necessary for brightness, though that will bring the current to around
21-22mA). Does anyone have a quantitative feel for how the higher current will
affect LED life? Based on the "perfect" scenario, they should last around
50,000-100,000 hours (these are probably standard numbers). I won't need them on
full time, so if I could get a quarter of that, it would more than suffice. Heat
dissipation should not be a problem.


later,
Kevin

"Watson A.Name - 'Watt Sun'" wrote:

Quote:
In article <3F06264D.4BB9FCE5_at_charter.net>, dressel1_at_charter.net
mentioned...

[snip]

Quote:
If you put the LED across the 3.6V, you should *still* put a current
limiting resistor in series with it. If you don't, then the battery
is probably pushing much more than the 30 mA maximum thru the LED.
Watch out for the overly hot LED.

Thanks,
Kevin

[snip]

--
@@F_at_r_at_o_at_m@@O_at_r_at_a_at_n_at_g_at_e@@C_at_o_at_u_at_n_at_t_at_y@,@@C_at_a_at_l@,@@w_at_h_at_e_at_r_at_e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t_at_h_at_e@@a_at_f_at_f_at_l_at_u_at_e_at_n_at_t@@m_at_e_at_e_at_t@@t_at_h_at_e@@E_at_f_at_f_at_l_at_u_at_e_at_n_at_t@@


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