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Sine to square wave converter
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quanghoc@gmail.com
electronics forum beginner


Joined: 14 Aug 2006
Posts: 13

PostPosted: Tue Aug 22, 2006 4:28 pm    Post subject: Adjustable Carbon Attenuator Reply with quote

I looked at this Attenuator:
http://www.vishay.com/docs/32025/m2001h.pdf

And there are some specification I don't understand. So what is
Resistive Element? I wonder if it is always "Carbon on laminated
paper"!!? If so, why they put it in there? Same question to Wiper
Contact.. isn't it always "Metal"??

Thanks.
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simo.kaltiainen@sunpoint.
electronics forum addict


Joined: 20 Mar 2006
Posts: 51

PostPosted: Tue Aug 22, 2006 3:55 pm    Post subject: Re: Just a question Reply with quote

Tim Williams wrote:
Quote:
Voltage doesn't matter if the output is in fact more like constant current
(or current limited). In that case, voltage will rise to whatever it
ultimately wants to.

Yes, if it's constan current or current limited, but if it's a constant
voltage charging (like lead batteries usually), I was actually still
wrong, as it's not the effective voltage even then that matters. But
it's the effective time, which is increased by the cap (without filter
cap the battery gets charged only at the peaks of the pulsating
voltage, but with a filter cap added, it makes the voltage steady,
charging the battery all the time).
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ehsjr
electronics forum Guru


Joined: 03 May 2005
Posts: 863

PostPosted: Tue Aug 22, 2006 3:50 pm    Post subject: Re: Will this DC motor control work? Reply with quote

Eric R Snow wrote:
Quote:
Greetings All,
I have been trying all sorts of designs out in my head for
controlling wire feed speed. The goal is to have a push-pull wire feed
system in a small MIG welder. The pulling wheels should try to spin
just a little faster than the push wheels to keep the wire taught. I'm
thinking about 5% difference but with a slip clutch on the pull wheel.
The slip clutch will be adjusted so that it slips before the wheel
slips on the wire. I have built and tested the clutch and it works
well.
My latest plan is to use wheels spinning at identical speeds with
the pulling wheels being 5% larger in diameter. To keep the wheels
spinning the same a tach would be driven by the idler push wheel and
the output used to control the pull driver wheel.
By using the push idler wheel as the speed reference even if the
push drive wheel slips on the wire the idler wheel should not slip.
I think I've got the mechanical part figured out. However, does
this sound like a good plan electronically?
Thanks,
Eric R Snow

Belt or gear drive both wheels from a single motor.
Forget the electronics - not needed if you do that.

Ed
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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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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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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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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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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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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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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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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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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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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.

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http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
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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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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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