need help in Power Supply

[email protected]

we have a fax machine that is always busted whenever there's a power 
surge,so I suspected that the power supply of the fax machine is not 
regulated..instead of fixing it I decided to make one.
but the problem is all of my notes in electronics only gives me a 
20volts DC output which is not enough to supply the fax machine.
(it uses a 24vDC output)

Does anyone here have a circuit diagram of a regulated 24v Power 
Supply?

I will appreciate any help.

Thanks.

Re: new one

Thomas Lee Mullins

#59

--- In Electronics_101@y..., reniar@c... wrote:
Hello guys,

Im Buknoy,recently subscribe in this group.

Im a Electronics Technician for a quite sometimes now and I want to 
enhance my knowledge in electronics.,I hope this group will be a 
great help to me.

Thanks and good day to all.Have you tried the 
group? I am a member of more than one group (if one group can 
not answere a question, perhaps another [of the same type]can?).

new one

[email protected]

#58

Hello guys,

Im Buknoy,recently subscribe in this group.

Im a Electronics Technician for a quite sometimes now and I want to 
enhance my knowledge in electronics.,I hope this group will be a 
great help to me.

Thanks and good day to all.

Re: IC's?

Matt Hill

#57

checkout www.icmaster.com to find who makes the IC. 
Then go to the manufacturer website.
=]
matt hill

--- Zach Archer <slander@...> wrote:
Oh yeah -- I also got a few IC's in the package. Is
there a directory 
(online or otherwise) that can identify their
function, and 
(hopefully!) indicate what the pins do? Thanks

-- Z

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multimeters' funcionality testing jig

[email protected]

#56

I need to build a jig using an AC source from outside to see if a 
multimeter is functional. Have to design it to be able to test 
resistance, cap, current both AC and DC, voltage, diodes.
Does anybody know where could I find some schematics to help me?
Thanks 
Michael
.

More transformers...

Zach Archer

#55

I generated low-level AC voltage using a sound program on my computer -- I looped a 60 hz sine wave, and ran it through my mixer for amplification, and then into the transformer. On this side, the voltmeter read 2 volts rms AC. The other side of the transformer read 1/3 of a volt, which would indicate a 1:6 ratio stepping down. BUT...

I tried flipping the transformer around, which ought to have changed its ratio to 6:1, right? And it gave me the same reading, 2 volts in, 1/3 volt out. Hmmm.

The other model of transformer (the one with 11 pins) gave me a surprise -- the incoming side read 4 volts rms AC, and I couldn't find any current or voltage whatsoever on the other side. Confusing! Time to search the web, I guess, and see if I can determine more info about these components based on their ID numbers...

-- Z

Re: Evaluating a transformer?

[email protected]

#54

Zach,  try AC voltage, Good Luck, Steve

Show quoted text

At 05:44 PM 5/18/01 -0700, you wrote:
Greetings all, I won a small box of assorted electronic components on
eBay, which arrived today. I'm still trying to evaluate + test all of
them, but I have a question regarding transformers. The box came with
many small transformers, 2 different kinds -- the smaller kind has 5
leads (3 on one side, 2 on the other) and the larger ones have 11
leads (6 and 5).

I'm trying to determine the turns ratio of both models. Unfortunately
I'm not having any luck... What I'm doing is setting a variable DC
power supply to either 6 or 3 volts, and connecting that to 2 wires
on one side of the transformer. On the other side I'm attaching a
5-watt, 100-ohm resistor to a couple leads. (The leads are being
chosen semi-randomly...)

Then I'm measuring the DC voltage on both sides. The primary side
(er, the side with the power supply connected to it... This is
another unknown, I'm not sure which side steps the voltage up, and
which steps down?..) responds okay, it measures the DC input, minus a
few volts.

The other side, however, always registers as dead, I'm not measuring
any voltage across the resistor at all.

Any ideas? The small transformer got warm, which at least indicates
that it's doing something, but the large one stays cool...

-- Z

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Electronics_101-unsubscribe@...



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Re: IC's?

Tavys Ashcroft

#53

Oh yeah -- I also got a few IC's in the package. Is there a directory
(online or otherwise) that can identify their function, and
(hopefully!) indicate what the pins do? ThanksWell, aside from just looking up the part number on google, there's:

The Chip Directory

and

Semiconductor Cross Reference Search

Each usefull in a different way.

Zach, email me which chips you have and I'll come up with a fun circuit or project for you.

-Tavys

Re: Evaluating a transformer?

Tavys Ashcroft

#52

Then I'm measuring the DC voltage on both sides.Well there's your problem right there.  Transformers only work for AC.  It's inductive coupling.  As the primary's voltage goes up and down, a magnetic field expands and collapses.  This magnetic field's velocity induces voltage in the winds of the secondary, giving your your secondary voltage.  When it's only DC, the magnetic field is constant, and so there's no change in the magnetic field to create movement in the electrons.

Any ideas? The small transformer got warm, which at least indicates
that it's doing something, but the large one stays cool...Well, the warmth is created by the resistance of the wire.  It's usually pretty thin gauge wire, which has been dipped in varnish and baked to keep winds from shorting.  I make large inductors at work similar to this, but they weigh 300 pounds.  Sometimes we 'DC Bake' them.  The heat from DC current will cook off any wet varnish solvent inside after we bake them in a large oven.  Mmmm Xylene eating my brain cells.

So, if you want to evaluate a transformer, you're going to need a sine wave generator.  Any AC will do, but a sine wave is a good place to start.  Plus, you get to turn the knob and make space sounds. Outer space sounds like someone turning a knob on an oscillator, by the way.

Then you use your multimeter in AC mode and measure primary and secondary voltage.

The one with five wires is probably center tapped, which means you get full secondary voltage across the two outer wires, but half of that from the center wire to either outer one.  Center tapped transformers are usually used in non-bridge full wave rectifier circuits for DC power supplies and such.

-Tavys

IC's?

Zach Archer

#51

Oh yeah -- I also got a few IC's in the package. Is there a directory (online or otherwise) that can identify their function, and (hopefully!) indicate what the pins do? Thanks

-- Z

Evaluating a transformer?

Zach Archer

#50

Greetings all, I won a small box of assorted electronic components on eBay, which arrived today. I'm still trying to evaluate + test all of them, but I have a question regarding transformers. The box came with many small transformers, 2 different kinds -- the smaller kind has 5 leads (3 on one side, 2 on the other) and the larger ones have 11 leads (6 and 5).

I'm trying to determine the turns ratio of both models. Unfortunately I'm not having any luck... What I'm doing is setting a variable DC power supply to either 6 or 3 volts, and connecting that to 2 wires on one side of the transformer. On the other side I'm attaching a 5-watt, 100-ohm resistor to a couple leads. (The leads are being chosen semi-randomly...)

Then I'm measuring the DC voltage on both sides. The primary side (er, the side with the power supply connected to it... This is another unknown, I'm not sure which side steps the voltage up, and which steps down?..) responds okay, it measures the DC input, minus a few volts.

The other side, however, always registers as dead, I'm not measuring any voltage across the resistor at all.

Any ideas? The small transformer got warm, which at least indicates that it's doing something, but the large one stays cool...

-- Z

Re: Thelephone line modulation with tv signal

Barry Hansen

#49

The audio bandwidth over telephone connections is too low to support full-motion video. However, amateur radio operators have been sending color pictures over the airwaves using the small audio bandwidth for many years. This would work just as well over the telephone. Read about SSTV (slow scan television) which sends pictures with audio modulation. It fits neatly within a 2.6 kHz bandwidth, and is suitable for telephones and all sorts of audio recordings. Search the Internet for SSTV and you'll get lots of hits, such as this one: To make the pictures fit into audio, each frame takes a few seconds to a couple minutes, depending on the picture's resolution and number of colors. You give up motion, but the pictures are quite nice. Equipment? SSTV can be built quite cheaply using a computer with a sound card. Free software is available from ham radio web sites. There is another alternative, too. If you're going to use a computer anyway, then an ordinary modem connection is better optimized to send data and digital pictures across the phone lines. Good luck, Barry

Show quoted text

I want to send a video by telephone line, but i dont know how to
start. I'm looking for a circuit that modulate the telephone line with a
video sinal and at the other end it demodulate to see this image in
a tv. Please if any one can give me an idea or help, send me that.

Re: Thelephone line modulation with tv signal

Tavys Ashcroft

#48

I want to send a video by telephone line, but i dont know how to
startWell, first you should learn a bit about the nature of a video signal, and the frequency response of telephone systems.  The audio in telephones is of a very limited band.  Something like 500-3000 Hz (don't quote me on that, I don't actually know it).  So what you need is something that can perhaps digitize your video signal.  Real analog video signals are at a very high frequency which would never make it across a phone system.  With a digital signal, you'd need the sampling rate to be within the audio range of the telephone system, but would otherwise probably not have a problem.  The drawback of that is having such a low sampling rate leads to low quality and low frame rate.  That's why nobody has a good looking video telephone yet.


im lookin for a circuit that modulate the telephone line with a
viedo sinal and at the other end it demodulate to see this imagen in
a tv.I'm sure it's possible to make..something..but don't count on high quality.  The phone system is one of the least reliable systems as far as quality goes.  Nearest I can see is some sort of complicated audio range beat frequency type thing but it would probably be next to impossible to make, forgetting the distortion and signal loss over phone lines.

You'd be better off going digital.

I'm no expert on analog to digital stuff, but I know there are lots of analog to digital chips available.  You'd just lose a whole lot of quality for the low sampling rate necessary.

What exactly were you planning on doing with this.  Maybe there's a better way to transmit..?

-Tavys

Re: Thelephone line modulation with tv signal

nKode

#47

开云体育

oh, btw, they sell things for old tv's that have a coax to a two wire split forked piece that you screw down... I've got one for an old console that's not cable ready. They're real common. Considering a telephone wire only requires a ring and a tip, two wires, circuitry shouldn't be required....just get the adapters.

?

Joshua

?

----
"A meow massages the heart."?
nKode / Pulse 8 - aim:jkerseyVCSO

?

Show quoted text

----- Original Message -----

From: ramiroi@...

To: Electronics_101@...

Sent: Thursday, May 17, 2001 10:32 AM

Subject: [Electronics_101] Thelephone line modulation with tv signal

I want to send a video by telephone line, but i dont know how to start im lookin for a circuit that modulate the telephone line with a viedo sinal and at the other end it demodulate to see this imagen in a tv. Please if any one can give me an idea or help, send me taht
To unsubscribe from this group, send an email to: Electronics_101-unsubscribe@...

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Re: Thelephone line modulation with tv signal

nKode

#46

开云体育

what's wrong with using a coax?!

?

Joshua

?

----
"A meow massages the heart."?
nKode / Pulse 8 - aim:jkerseyVCSO

?

Show quoted text

----- Original Message -----

From: ramiroi@...

To: Electronics_101@...

Sent: Thursday, May 17, 2001 10:32 AM

Subject: [Electronics_101] Thelephone line modulation with tv signal

I want to send a video by telephone line, but i dont know how to start im lookin for a circuit that modulate the telephone line with a viedo sinal and at the other end it demodulate to see this imagen in a tv. Please if any one can give me an idea or help, send me taht
To unsubscribe from this group, send an email to: Electronics_101-unsubscribe@...

Your use of Yahoo! Groups is subject to the .

Thelephone line modulation with tv signal

[email protected]

#45

I want to send a video by telephone line, but i dont know how to 
start im lookin for a circuit that modulate the telephone line with a 
viedo sinal and at the other end it demodulate to see this imagen in 
a tv. Please if any one can give me an idea or help, send me taht

Re: D/C speed control

Tavys Ashcroft

#44

Can anyone suggest a way to control speed of a D/C motor, inexpensively?  It
cannot be 'Mickey mouse' because it's part of a prototype machine I'm
building, which hopefully will sell to the public.  Is it a fact of life
that it just costs to cut the voltage?Well, you could do some experiments with pulse width modulation.  I hear that is used quite a bit for pulse DC motor control.  You can make this with a 555 timer circuit like this:

You can set up a voltage divider with a pot in the middle as your control resistor to get the exact range you want.

This may seem just a little 'mickey mouse' but it works.

If you want non pulse DC (I suppose for higher current motors that might be problematic...????) you could use an adjustable voltage regulator.  I know most manufacturers have these.  National Semiconductor has lots of info on their webpage including PDF files and application notes and circuits.

You could design your own voltage controlling board for the motor speed and have it custom made, but that could be just as expensive as buying the premade ones.

I know your pain, though.  There's a few machines I make at work that use DC motor control boards for adjusting conveyor belt speed.  Very expensive.

-Tavys

Multi code DVD????

#43

Can Any one give me Any info on how to mod DVD players so they are
multi code?????

)O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(  )O(

     The Sinister Dragon

Hey, Just because I'm EVIL,
     Doesn't make me a bad person......    >:-)

D/C speed control

Gary F

#42

Hello.

I'm trying to run a 24v D/C gear motor with the ability to control RPM
between 20 - 35.  Continuous operation, 9 hours per day.

50 inch oz. of torque.  Looking at the Molon C15, or other type of 'gear
motor' that I can attach a nose gear to the shaft.  Speed control is
mandatory.

My problem is in the controller itself.  EXPENSIVE.  I'm now looking into
model railroad controllers to do the job.  They are bigger than the normal
KB controllers, but half the cost.

Can anyone suggest a way to control speed of a D/C motor, inexpensively?  It
cannot be 'Mickey mouse' because it's part of a prototype machine I'm
building, which hopefully will sell to the public.  Is it a fact of life
that it just costs to cut the voltage?

Thanks.

Gary

(No subject)

Ed Miller

#41

I have a large quantity of used Futaba M202SD08
standard character display modules (vacuum flourescent
displays or VFDs) for sale for $15.00 each, with free
shipping.

(Free shipping applies to US buyers only. Non-US
buyers - Please contact me to make special shipping
arrangements, as you will be responsible for any
charges beyond normal US shipping).

On my VFD page at
 you'll
find photos, specifications, a link to the operations
manual in PDF format so you can download the manual
free, a link to Futaba for further information, my
eBay buyer / seller ratings, and more.

These VFDs can be used in a variety of applications
such as BASIC STAMPS, 80C52-BASIC controllers, PCs,
robotics, PICs, PLCs, miscellaneous projects for the
electronics hobbyist and experimenter, and more.

These displays were removed from good equipment
because they weren't "showroom new". A few of the
pixels are slightly dim, but each has been
individually tested and found to be in good working
order.

Each module comes with a 30-day guarantee (minus
return shipping charges) if returned in undamaged
condition with your sales receipt.

They may not be suitable for production use, but they
are a terrific bargain for experimenters, developers,
and hobbyists. 

These VFDs retail new for $70-90 each, but I am
offering good used ones for about 1/4th that price.
Only $15.00 each, shipping included.

I accept personal checks and money orders, or you can
use your credit card securely via PayPal to order.

If you have any questions, please feel free to contact
me.

William E. (Ed) Miller, ASEET
11 N. Washington Street
Chesterfield, Indiana 46017 USA
(765) 378-0358 (evenings)

prototech@... (main e-mail)
coolcreek.geo@... (alternative e-mail)



=====
William E. (Ed) Miller
coolcreek.geo@...
prototech@...

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