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Sine to square wave converter
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my.spam.maps@gmail.com
electronics forum beginner


Joined: 22 Aug 2006
Posts: 1

PostPosted: Tue Aug 22, 2006 5:55 am    Post subject: Re: BALUN transformer for capacitive loads Reply with quote

can you rephrase that?

archiees@gmail.com wrote:
Quote:
Hi,
I need to drive 2 capacitive electrodes with out of phase RF (0-100
Vp-p, 10KHz - 1MHz). For this purpose i got myself one of the T&C power
amplifiers (AG1021) with a gain of 53dB upto 1MHz. I planned to use a
BALUN transformer from North hills (75 ohm: 75 ohm, 1KHz - 2MHz) to
unbalance the amplifier RF. I use a function generator as a source.
However, things are not working as i thought.
The setup is as follows: Function generator feeding the signal to the
power amplifier. The output i measure on a oscope is good 100 Vp-p for
small input signal < 1 m volt (10Khz) . As soon as i connect the output
of the amplifier to the BALUN, my reflected power to the amplifier
shoots up. And the 2 unbalanced outputs of the BALUN show merely 12
Vp-p.
I know the power amplifier is rated for 50 ohm, is there an impedance
problem. With the capacitive load at the secondary of the BALUN, the
impedance which the amplifier at the primary is surely not 50 ohms.
How can i overcome this, can i just use a BALUN with more turns on the
secondary? Say 50 ohm : 600 Ohms BALUN to step up the voltage.
I would appreciate the suggestions.
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John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Tue Aug 22, 2006 6:15 am    Post subject: Re: BALUN transformer for capacitive loads Reply with quote

my.spam.maps@gmail.com wrote:
Quote:
can you rephrase that?

archiees@gmail.com wrote:

Hi,
I need to drive 2 capacitive electrodes with out of phase RF (0-100
Vp-p, 10KHz - 1MHz).

(snip)

Quote:
I know the power amplifier is rated for 50 ohm, is there an impedance
problem. With the capacitive load at the secondary of the BALUN, the
impedance which the amplifier at the primary is surely not 50 ohms.

That's right. with a capacitive load, the load impedance falls as
frequency rises. Using a transformer to change an unbalanced source
to a balanced pair of outputs does nothing to solve this mismatch.
The largest capacitance the unbalanced 50 ohm load can drive to
nominal output voltage at 1 MHz is about 3000 pF. If the balun steps
the total voltage up 2:1 then the capacitance each side can drive is
half of that.

So what capacitive load are you trying to drive to 100 v p-p at up to
1 MHz?
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jasen
electronics forum Guru Wannabe


Joined: 18 Jun 2006
Posts: 204

PostPosted: Tue Aug 22, 2006 7:08 am    Post subject: Re: Schumacher Automotive Jump Stater/DC Power Source and Macerator Reply with quote

On 2006-08-21, mea305 <mea305@aol.com> wrote:

Quote:
The page does not explain all of the information; according to the
material sent with the unit, it operates at 12VDC, 16Amps (with a 20
Amp fuse in the "trigger."

If, then, I use a standard automotive battery (will it be a difference
whether the auto battery is "good")?

Get a used battery from a wrecker (the ones they sell for $10 or so with a one
month warranty), it'll be good enough.

what happened to the battery in your RV?

Bye.
Jasen
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jasen
electronics forum Guru Wannabe


Joined: 18 Jun 2006
Posts: 204

PostPosted: Tue Aug 22, 2006 7:47 am    Post subject: Re: transistor help Reply with quote

On 2006-08-21, Imran <messenger_boy_2005@hotmail.com> wrote:
Quote:
I have a home irrigation controller hat has gone faulty on one of the zones,
I have opened it up and have found one of the transistors to be faulty there
is a number on the transistor but it looks like its a part number from the
manufacturer of the irrigation unit rather then the actual part number of
the transistor.

The number written on it is 1401ES or 1401E5 cant make out if its a 5 or an
S but looks like an S to me and sound like it might be an NPN transistor.

those things are often AC, are you certain it's not a triac?

Quote:
The purpose of this transiston from what I can tell from the board is to
turn a solenoid on and off.

If you can tell the current and voltage the solenoid operates at that would
help. (or the current output of the power supply for the irigation unit...)

Quote:
The Irrigation unit is made by Holman Distributors.

that's a novel name for a manufacturer.

Bye.
Jasen
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jo.jo
electronics forum beginner


Joined: 22 Aug 2006
Posts: 3

PostPosted: Tue Aug 22, 2006 10:17 am    Post subject: Bridge Rectifier Problem.......!!!!!!! Reply with quote

I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?
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default
electronics forum Guru Wannabe


Joined: 03 May 2005
Posts: 175

PostPosted: Tue Aug 22, 2006 10:50 am    Post subject: Re: 240V relay contact suppression Reply with quote

On Mon, 21 Aug 2006 22:44:44 GMT, Stanislaw Flatto
<compaid@shoalhaven.net.au> wrote:

Quote:
John Fields wrote:

Actually, no.

The diode provides a path to Vcc for the high-voltage spike
generated when the relay driver turns off, in order to protect the
driver. The price, though, is that the current won't only flow
through the diode, it'll also flow through the coil (since that's
where it comes from) until it's dissipated to the point where it can
no longer hold the armature closed. That means that the relay will
stay closed longer than if the diode wasn't there, but the driver
won't be destroyed.



Too modern for me. What "driver"?
~1960 AD working on telephone exchanges, relay technology, diodes(?),
were called rectifiers then, selenium plates, and were used (rarely!)
to improve responses by allowing faster collapse of the magnetic field.
Anything changed since?

Have fun

Stanislaw

Solid state transistor drivers are/can be destroyed by the voltage
spike caused by the collapsing magnetic field. Back in the selenium
rectifier era, they used toobs which were unaffected by the spikes.

The diode acts to short the reverse emf developed by the coil and this
supports the magnetic field for a short period of time, slowing the
action of the contacts opening. - similar to a the shading pole they
use on AC relays to prevent them from chattering.

Slower collapse - the diode causes a current to flow in the coil, that
current produces a magnetic field.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
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Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Tue Aug 22, 2006 11:25 am    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

"jo.jo" wrote:

Quote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?

Not enough info sadly.

Is there anywhere you can post a schematic showing what you did?

Graham
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Stanislaw Flatto
electronics forum addict


Joined: 10 Sep 2005
Posts: 74

PostPosted: Tue Aug 22, 2006 1:08 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

jo.jo wrote:
Quote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?


Can you be more specific.
Do you see half sinusoic signals of the same polarity and twice the
frequency of input?
Or you see half sinusoic signals with the period of input and missing
equal periods between them?

If the first then you have correct "full wave rectification". What did
you expect?

HTH

Stanislaw
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John Fields
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3260

PostPosted: Tue Aug 22, 2006 1:14 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

On 22 Aug 2006 03:17:18 -0700, "jo.jo" <jo.jo.uk@hotmail.co.uk>
wrote:

Quote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?


---
You probably have something miswired or a diode in backwards. The
circuit should look like this:

(View in Courier)


+----------+------>+DC
|K |K
[1N4001] [1N4001]
| |
120AC>--------+ +--+ |
P||S | |
R||E | |
I||C | |
120AC>--------+ +--|----------+
| |
|K |K
[1N4001] [1N4001]
| |
+----------+------>-DC

"K" is the diode cathodes, and with your scope ground connected to
-DC and the probe to +DC you should see full-wave rectified AC


--
John Fields
Professional Circuit Designer
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Bob Masta
electronics forum Guru Wannabe


Joined: 03 May 2005
Posts: 219

PostPosted: Tue Aug 22, 2006 1:28 pm    Post subject: Re: Data logger using PDA - advice needed Reply with quote

On 19 Aug 2006 15:38:27 -0700, "Pashlipops" <nickpashley@hotmail.com>
wrote:

Quote:
Hi there

I am looking for some advice as to where to start to put my iPaq 2200
to work as a datalogger.

As a person with little electronics knowledge and experience (but I am
willing to learn), I want to connect the following:

signal -> voltage -> multiplexer -> RS232 (or USB) interface -> iPaq -

CF card

I am looking to log about 10 channels at 5-10Hz. I can probably deal
with the signal to voltage interfaces, some being frequency to voltage,
others temperature, others pressure etc.

I have downloaded the Microsoft eMbedded tools (VB and C++) which will
(hopefully) allow me to write an application for the iPaq.

My question for you guys is; can anyone point me in the right direction
for circuit diagrams/designs for multiplexers that can connect via
RS232 or USB? Or even a DIY project to do the whole job.

Thanks in advance

PP

You might want to check out Dataq's cheap (US$25)

A/D module at:
http://www.dataq.com/194.htm
This interfaces through the serial port and comes
with Windows data logger software. Don't know if
it will work with the iPaq. This Dataq product has been
around in various forms for many years, so I'm guessing
that by now the software interface may be well-hacked...
you may be able to make a driver for your own software.
I looked into this myself back when the thing was new,
(and free!) but the interface was more than I wanted to
hack out at the time.

Best regards,



Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
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jo.jo
electronics forum beginner


Joined: 22 Aug 2006
Posts: 3

PostPosted: Tue Aug 22, 2006 1:52 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

Stanislaw Flatto wrote:
Quote:
jo.jo wrote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?


Can you be more specific.
Do you see half sinusoic signals of the same polarity and twice the
frequency of input?
Or you see half sinusoic signals with the period of input and missing
equal periods between them?

If the first then you have correct "full wave rectification". What did
you expect?

HTH

Stanislaw

the output signal from my rectifier consists of positive half of a sin
wave and then a flat line ( 0v more or less ) and is the same frequency
as the input. a bridge rectifer essentially takes a sine wave and
inverts the negative half, hence the frequency doubles. this inverted
negative half is what i am missing from my output.

i bread boarded the rectifier ( made from four 1n4001 ) and applied a
sin wave from a signal generator to the input and measured the output
on a oscilloscope. the output from the rectifier seems to be missing
the inverted negative half cycle.

i thought mayby it has something to do with the way the oscilloscope
and signal generator ground there signals or i am simply using the
equipment wrong. however i am sure that i have set everthing up
correctly

i am using 15V at 50 Hz to test the bridge rectifier and the amplitude
of the output ( for the posistive half of the input ) is consistant
with the conversion from rms to peak values and the losses you would
expect in the diodes.
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MarkMc
electronics forum beginner


Joined: 25 May 2005
Posts: 49

PostPosted: Tue Aug 22, 2006 2:38 pm    Post subject: Re: 240V relay contact suppression Reply with quote

Yes, the LCR (combined cap and Resistor) and MOV are rated for about
400VAC (I don't have the items here with me at work to confirm).

Thanks
Mark

John Popelish wrote:

Quote:
That should work if both the capacitor and MOV is rated for 240 volts
AC operation. If the capacitor is not AC rated, it should have
something like a 1000 volt DC rating (or at least as high as the MOV
clamping voltage specification).
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petrus bitbyter
electronics forum Guru


Joined: 24 Mar 2005
Posts: 363

PostPosted: Tue Aug 22, 2006 2:45 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

"jo.jo" <jo.jo.uk@hotmail.co.uk> schreef in bericht
news:1156254767.795356.33040@75g2000cwc.googlegroups.com...
Quote:

Stanislaw Flatto wrote:
jo.jo wrote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?


Can you be more specific.
Do you see half sinusoic signals of the same polarity and twice the
frequency of input?
Or you see half sinusoic signals with the period of input and missing
equal periods between them?

If the first then you have correct "full wave rectification". What did
you expect?

HTH

Stanislaw

the output signal from my rectifier consists of positive half of a sin
wave and then a flat line ( 0v more or less ) and is the same frequency
as the input. a bridge rectifer essentially takes a sine wave and
inverts the negative half, hence the frequency doubles. this inverted
negative half is what i am missing from my output.

i bread boarded the rectifier ( made from four 1n4001 ) and applied a
sin wave from a signal generator to the input and measured the output
on a oscilloscope. the output from the rectifier seems to be missing
the inverted negative half cycle.

i thought mayby it has something to do with the way the oscilloscope
and signal generator ground there signals or i am simply using the
equipment wrong. however i am sure that i have set everthing up
correctly

i am using 15V at 50 Hz to test the bridge rectifier and the amplitude
of the output ( for the posistive half of the input ) is consistant
with the conversion from rms to peak values and the losses you would
expect in the diodes.


Suppose the output of your signal generator and the input of your
oscilloscope share a common ground.

petrus bitbyter
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John Fields
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3260

PostPosted: Tue Aug 22, 2006 3:22 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

On 22 Aug 2006 07:54:34 -0700, "jo.jo" <jo.jo.uk@hotmail.co.uk>
wrote:

Quote:

petrus bitbyter wrote:

Suppose the output of your signal generator and the input of your
oscilloscope share a common ground.

petrus bitbyter

Both of them are grounded so yes they do how would this be a problem ?

---
They're shorting out a diode in the bridge.


--
John Fields
Professional Circuit Designer
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jo.jo
electronics forum beginner


Joined: 22 Aug 2006
Posts: 3

PostPosted: Tue Aug 22, 2006 3:40 pm    Post subject: Re: Bridge Rectifier Problem.......!!!!!!! Reply with quote

jo.jo wrote:

Quote:
I am trying to construct a small desktop power supply and have noticed
a small problem when measuring the output voltage from my bridge
rectifier. The rectifier is constructed from four 1N4001. When i
apply a AC wave (sin) to the input and measure the output, using a
oscilloscope, the bridge rectifier seems to produce only halfwave
rectification. I was expecting full wave rectification. Can anyone
suggest what i am doing wrong ?

thanks to john, petrus and everyone else who replied i am sure you will
hear from me again..... ;- )
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Google

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