Please help with "Voltage divider with capacitor circuit" fr

[lucretia]

Hi,

I bought this book, have all the bits and am trying to follow along.
I'm on chapter 5 (IC's) and implemented the flashing LED circuit in
Fig 5.2. I've implemented the circuit in Fig 5.6 where the LED is
replaced by a resister and capacitor. Problem is, I get the same
results, except for when I substitute the last capacitor (1nF). I just
don't get the 4.2V or 4V from the next 2 experiments, where C2 is
100nF and 10nF respectively. I've no idea why, either. Now, the
capacitor I'm using says 1n0K63 on it and I'm sure that is the same as
1nF = 1n0 = 1.0nF, right?

Can anyone help me?

Thanks,
Luke.

 

[JeffM]

lucretia wrote:

I bought this book, have all the bits and am trying to follow along.
I'm on chapter 5 (IC's) and implemented the flashing LED circuit in
Fig 5.2[. . .]
Luke

ASSuMEing that everyone (or, indeed, ANYone) has that book
is quite an imposition on the group.

The way to get good help is to put up a copy of the *schematic* here
so that EVERYONE can see it.

One way (the easy way) to do that is
1) Make a *.GIF or *.PNG of the original
using a scanner or digital camera.

2) Upload that image to a "image hosting service".
http://google.com/search?q=cache:aTbadBKF1cgJ:www.dmoz.org/Computers/Internet/On_the_Web/Web_Applications/Photo_Sharing/Image_Hosting+hotlinking+sister+*-*-emphasis-on-free-speech+registration+limit+Last+uncensored+Image.Hosting&strip=1

3) Put a hyperlink to that image in your Usenet post
(this is NOT "Google Groups")
http://groups.google.com/group/alt.comp.freeware/msg/4a83eaad102e7efe?q=*-a-service-for-*-*-*+Usenet+*-Wikipedia+hide.the.fact+*-*-policed+concerns-*-*-*-*-about-the-Google-interface+*-*-follow-Usenet-customs-and-*-rules+*-*-*-not-*-mustered-*-*-*-*-*-*-*-*-*-*-*-*-*+*-*-*-*-*-*-*-software+less-*-savvy-*+*-*-*-*-*-*-*-*-*-*-*-*-is-now-legendary+zzz+*-summary+qq+Web
and _deep-link_ to the **image**--NOT to the *page*.
..
..
Another way (a BETTER way) is to use ASCII characters
to draw your circuit within your post:
http://groups.google.com/group/sci.electronics.design/browse_frm/thread/85e131e3a52c30bf/8f0442f3d583fe45?q=PNG+ASCII+freeware.tool+*-*-*-*-GRATICULE+AVOID.JPEG+binaries+Andreas.Weber+website+zzz+PDF+GIF+persistance+LTspice+qq-qq+alt.binaries.schematics.electronic+asc-file

You MUST use software that allows a monospaced font (like Courier).
e.g. The Kate text editor will do this.
This software makes this even easier:
http://translate.google.com/translate?u=http://www.tech-chat.de/aacircuit..html+&langpair=de%7Cen

If you attempt to do this in Google's font
rather than cut & paste from non-proportional font editor
the results will be a complete mess.

(When you paste it into Google it will appear a mess to you.
It won't to those using a real Usenet newsreader.)

 

[Jon Kirwan]

On Tue, 17 Feb 2009 03:08:56 -0800 (PST), lucretia
<lucretia9@lycos.co.uk> wrote:

The following ASCII can be cut n pasted into a new file and loaded
into LTspiceIV, it's probably not the neatest, but I couldn't find a
way of rearranging the pins on the 555.

You didn't include a ground on the schematic and LTSpice kind of wants
that placed somewhere in order to simulate it.

As you have it, C1 participates in setting the period. You didn't
specify a value on the schematic, so I just used 10uF as a default. C2
modifies the tau (duration) of the pulse you observe on an
oscilloscope. If you are using a multimeter, though, you are probably
going to have a hard time observing it unless C2 is pretty large and
even then you will "observe" some kind of averaging, probably. Do you
have a scope or logic analyzer of some kind to use? That may help a
lot with looking at the results of what you are building.

Jon

 

[lucretia]

On Feb 17, 11:27 am, Jon Kirwan <j...@infinitefactors.org> wrote:

On Tue, 17 Feb 2009 03:08:56 -0800 (PST), lucretia

lucret...@lycos.co.uk> wrote:
The following ASCII can be cut n pasted into a new file and loaded
into LTspiceIV, it's probably not the neatest, but I couldn't find a
way of rearranging the pins on the 555.

You didn't include a ground on the schematic and LTSpice kind of wants
that placed somewhere in order to simulate it.

Well, I'll look into that

As you have it, C1 participates in setting the period.  You didn't
specify a value on the schematic, so I just used 10uF as a default. C2

C1 is switched between 10 microF, 1 microF, 100 nF, 10 nF and 1 nF. In
his results, he gets 0V, 0V, 1.5V, 4V and 4.2V respectively, this is
when C2 = 100 nF. I match these results except for the last one where
I get something like 0.14V. My multimeter is set to 20V AC range.

Also, when C2 is 10 nF, he gets: 0V, 0V, 0V, 1.5V and 4V for the
above, again, my last reading doesn't match.

modifies the tau (duration) of the pulse you observe on an
oscilloscope.  If you are using a multimeter, though, you are probably
going to have a hard time observing it unless C2 is pretty large and
even then you will "observe" some kind of averaging, probably.  Do you
have a scope or logic analyzer of some kind to use?  That may help a
lot with looking at the results of what you are building.

Nope, just a DMM.

Thanks,
Luke.

 

[lucretia]

I didn't know of some of these tools, thanks.

The following ASCII can be cut n pasted into a new file and loaded
into LTspiceIV, it's probably not the neatest, but I couldn't find a
way of rearranging the pins on the 555.

Thanks,
Luke.

--- divider.asc ---

Version 4

SHEET 1 880 680

WIRE -160 -96 -336 -96

WIRE 16 -96 -160 -96

WIRE 384 -96 16 -96

WIRE -160 16 -160 -16

WIRE 352 16 -160 16

WIRE -160 64 -160 16

WIRE 112 64 48 64

WIRE 384 64 384 -96

WIRE 384 64 336 64

WIRE -336 96 -336 -96

WIRE 112 128 0 128

WIRE 352 128 352 16

WIRE 352 128 336 128

WIRE -160 176 -160 144

WIRE -32 176 -160 176

WIRE 112 192 80 192

WIRE 416 192 336 192

WIRE -160 208 -160 176

WIRE 0 208 0 128

WIRE 0 208 -160 208

WIRE -160 240 -160 208

WIRE 16 256 16 -96

WIRE 112 256 16 256

WIRE -32 320 -32 176

WIRE 416 320 416 192

WIRE 416 320 -32 320

WIRE -336 432 -336 176

WIRE -160 432 -160 304

WIRE -160 432 -336 432

WIRE -64 432 -160 432

WIRE 80 480 80 192

WIRE 80 560 80 544

WIRE 288 560 80 560

WIRE 80 576 80 560

WIRE -64 672 -64 432

WIRE 48 672 48 64

WIRE 48 672 -64 672

WIRE 80 672 80 656

WIRE 80 672 48 672

WIRE 288 672 80 672

SYMBOL Misc\\NE555 224 160 R0

SYMATTR InstName U1

SYMBOL res -176 -112 R0

SYMATTR InstName R1

SYMATTR Value 4k7

SYMBOL res -176 48 R0

SYMATTR InstName R2

SYMATTR Value 10k

SYMBOL res 64 560 R0

SYMATTR InstName R3

SYMATTR Value 1k5

SYMBOL cap -176 240 R0

SYMATTR InstName C1

SYMBOL cap 64 480 R0

SYMATTR InstName C2

SYMATTR Value 100n

SYMBOL Misc\\battery -336 80 R0

SYMATTR InstName V1

SYMATTR Value 9V

TEXT 288 608 Left 0 ;Multimeter to read 50V (AC)

 

[tomrei]

On Feb 17, 11:37 am, lucretia <lucret...@lycos.co.uk> wrote:

On Feb 17, 11:27 am, Jon Kirwan <j...@infinitefactors.org> wrote:

On Tue, 17 Feb 2009 03:08:56 -0800 (PST), lucretia

lucret...@lycos.co.uk> wrote:
The following ASCII can be cut n pasted into a new file and loaded
into LTspiceIV, it's probably not the neatest, but I couldn't find a
way of rearranging the pins on the 555.

You didn't include a ground on the schematic and LTSpice kind of wants
that placed somewhere in order to simulate it.

Well, I'll look into that

As you have it, C1 participates in setting the period.  You didn't
specify a value on the schematic, so I just used 10uF as a default. C2

C1 is switched between 10 microF, 1 microF, 100 nF, 10 nF and 1 nF. In
his results, he gets 0V, 0V, 1.5V, 4V and 4.2V respectively, this is
when C2 = 100 nF. I match these results except for the last one where
I get something like 0.14V. My multimeter is set to 20V AC range.

Also, when C2 is 10 nF, he gets: 0V, 0V, 0V, 1.5V and 4V for the
above, again, my last reading doesn't match.

modifies the tau (duration) of the pulse you observe on an
oscilloscope.  If you are using a multimeter, though, you are probably
going to have a hard time observing it unless C2 is pretty large and
even then you will "observe" some kind of averaging, probably.  Do you
have a scope or logic analyzer of some kind to use?  That may help a
lot with looking at the results of what you are building.

Nope, just a DMM.

Thanks,
Luke.

Hi Luke,

if you plot the FFT of your output voltage with your LTspice, you'll
see that with C1=10n, the output frequency is about 5.8kHz
but if you change the C1=1n, the FFT will show your output frequency
is about 57.4k Hz.
most of the DMMs will have a AC frequency measuring range. some 30kHz
even less.
so there is high probability that you DMM is not rated for that high
frequency measurement.
check the spec on that.
it's best to use a oscilloscope or analyzer for this type of
measurement.

hope it helps.

yours Ren

 

[lucretia]

I Just uploaded a photo of the breadboard:
http://farm4.static.flickr.com/3166/3290274155_cbe0a0eb9b_b.jpg

On Feb 18, 11:53 am, tomrei <tomrei2...@gmail.com> wrote:

if you plot the FFT of your output voltage with your LTspice, you'll
see that with C1=10n, the output frequency is about  5.8kHz
but if you change the C1=1n, the FFT will show your output frequency
is about 57.4k Hz.
most of the DMMs will have a AC frequency measuring range. some 30kHz
even less.
so there is high probability that you DMM is not rated for that high
frequency measurement.
check the spec on that.

The manual says:

AC Voltage
Frequency range: 50Hz to 500Hz

AC Current
Frequency range: 50Hz to 500Hz

Capacitance
Test Frequency: 2 dot 5 (where dot is a full stop in the middle
vertically, not like a decimal point)Hz Models PG012 & PG017

Frequency
Ranges (autoranging): Model PG017 - 2kHz to 15MHz

Mine is a PG017.

it's best to use a oscilloscope or analyzer for this type of
measurement.

hope it helps.

yours Ren

Well, if that explains why I'm getting different results for that one
capacitor, then yeah it does, thanks

Luke.