Chip with simple program for Toy

[John Bokma]

Dave wrote:

Well, an answer already came... My subjects work everytime.

Yeah, you are such a smart guy.

--
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[Bob Monsen]

wdflannery@aol.com wrote:

.-------------o---o----------.
| | | |
no switch |/ | |
o------o----| ' |
| | |> |/ ---
| | |-| - 3V minimum
| | |> |
'+ .-. | |
=== | | | ---
/-\ | | .-. -
| '-' ( X ) |
| | '-' |
| | | |
'------o----------o----------'

Nice work. But.... I'm trying to put this thing together for a
calculus book for junior high students to illustrate an exponential
function (starting from the DE characerizing the circuit) in nature, so
the circuit has to easy for anyone to wire up. Hence, no
transistors... etc.


If there is even 1 ohm of resistance in the cap, it'll suck up 0.5V, probably preventing your bulb from lighting at all.


I did take a few EE course in college, and as I recall caps always had
0 resistance. What are the facts? How about a 0.1 farad electrolytic?

Caps have both resistance (called ESR) and inductance (called ESL).

Here is a tutorial containing more that you ever wanted to know about
capacitors:

http://my.execpc.com/~endlr/index.html

BTW, if the students have access to multimeters, it's easier to just
have them take time measurements of voltage across a resistor in an RC
setup. 100uF + 1MEG ohm gives a time constant of 100, so measurements
are likely to end up looking exponential on a graph in a lab. Two
students, one saying 5, 10, 15, 20... the other recording voltage at
that time.

Also, the parts are much cheaper (except the multimeter, of course,
which they could share).

---
Regards,
Bob Monsen

 

[mike]

Thaqalain wrote:

This was test question for ems comapny,they don't describe
Volatge/Current Source?here is original question:
DC is safely applied to the primary of a transformer:
*When limiting resistance is in series with primary.
*When -------------------------Parallel------------.
*When neither of preceding applies

True or false?
Transformer cores are sized to be the smallest/lightest/cheapest
they can be and still not saturate at rated drive levels.

If true, then any significant amount of DC current is a bad thing.
Matters not whether it was placed there by Mr. Thevenin or Mr. Norton.
mike

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[R. Steve Walz]

Thaqalain wrote:

1)An 8 bit transistor register has output voltage of LHLHLHLH,What is
equivalent decimal number being stored?
(2) A 4 bit transistor registry has output voltage of HLHL,what binary
number and it's decimal equivalent is stored?

I am new in ems cos want to qualify test for entry.
--------------------------

If L is 0 and H is 1, and lsb is last, then:
LHLHLHLH is 010101 which is 85 = 0 + 64 + 0 + 16 + 0 + 4 + 0 + 1
HLHL is 1010 which is 10 = 8 + 0 + 2 + 0

-Steve
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[John Fields]

On 10 Jun 2005 08:12:37 -0700, wdflannery@aol.com wrote:

Or, better yet:


+-----> |
| |
| O
|+ |
[BAT] +------+
| |+ |
| [1F] [LAMP]
| | |
+--------+------+


I like it, but I think the (assumed) high cap resistance of the 1 f
double layer electric cap will prevent it from working.

---
Take a look at this:

http://www.elna-america.com/PDF/DZ-N.PDF

Note that the 1F unit has an internal resistance of less than or equal
to 0.12 ohms.

If you look up the spec's for a 1728 lamp (1.35V, 0.06A) it'll present
a resistance of about

E 1.35V
R = --- = ------- = 22.5 ohms,
I 0.06A

when it's hot, so that 0.12 ohm ESR in the cap is only going to "kick
in" and decrease the initial current through the lamp by about 5% when
the switch is opened.
---

If I use a 0.1 f electrolytic and the hot bulb has 5 ohms resistance I
can get a time constant of 0.5 seconds, which isn't what I was hoping
for but isn't bad. (If the electrolytic has negligible internal
resistance).

---
See above. With a 1F cap discharging into a lit bulb with a filament
resistance of 22.5 ohms in series with the cap's 0.12 ohm ESR one
would expect a time constant of about 22.5 seconds, but since the
lamp's filament resistance will be dropping as the cap's charge
becomes depleted and its output voltage decreases, the time constant
will be considerably shorter. How much shorter? I don't know, but if
I took a WAG I'd say by about a factor of two.

IMO, that would be an interesting experiment/ exercise for you or your
students to perform. That is, calculating the filament resistance by
measuring the current through it with different voltages across it,
and then determining the time constant of the system as the resistance
falls because of the decay of the capacitor voltage across the falling
filament resistance.

--
John Fields
Professional Circuit Designer

 

[Rich Grise]

On Fri, 10 Jun 2005 16:35:19 -0700, Bob Monsen wrote:

wdflannery@aol.com wrote:

I did take a few EE course in college, and as I recall caps always had
0 resistance. What are the facts? How about a 0.1 farad electrolytic?

Caps have both resistance (called ESR) and inductance (called ESL).

Here is a tutorial containing more that you ever wanted to know about
capacitors:

http://my.execpc.com/~endlr/index.html

BTW, if the students have access to multimeters, it's easier to just
have them take time measurements of voltage across a resistor in an RC
setup. 100uF + 1MEG ohm gives a time constant of 100, so measurements
are likely to end up looking exponential on a graph in a lab. Two
students, one saying 5, 10, 15, 20... the other recording voltage at
that time.

Also, the parts are much cheaper (except the multimeter, of course,
which they could share).

Be sure and use _analog_ multimeters, you know, the kind with a
meter needle? DVMs are almost useless for this sort of thing.

And I've done this very thing, except with a fairly large aluminum
electrolytic cap, maybe 1000 - 10000 uF (I don't remember the exact
value), ~24 VDC, and an LED + 1K resistor. The voltage across the
resistor was 1V per mA, of course.

I was amazed - from 20 mA down to 10 mA, the brightness seemed not
to change _at all_, at least to the naked eye (shame on you! Put
some clothes on!) over a period of about a second, and then decreased
practically linearly from 10 mA to zero. I _saw_ the knee at 10 mA! I
even turned off the room lights, where the LED was the only light in the
room, and the LED just kept dimming, and dimming, and dimming, until there
was zero light at zero current.

Cheers!
Rich

 

[John Bokma]

Dave wrote:

I know, and you're the way too smart, arrogant,

No, you got your feelings messing up your brain cells (all 4 of them)
again.

--
John MexIT: http://johnbokma.com/mexit/
personal page: http://johnbokma.com/
Experienced programmer available: http://castleamber.com/
Happy Customers: http://castleamber.com/testimonials.html

 

[Rich Grise]

On Fri, 10 Jun 2005 16:49:04 -0700, mike wrote:

Thaqalain wrote:
This was test question for ems comapny,they don't describe
Volatge/Current Source?here is original question:
DC is safely applied to the primary of a transformer:
*When limiting resistance is in series with primary.
*When -------------------------Parallel------------.
*When neither of preceding applies


True or false?
Transformer cores are sized to be the smallest/lightest/cheapest
they can be and still not saturate at rated drive levels.

If true, then any significant amount of DC current is a bad thing.
Matters not whether it was placed there by Mr. Thevenin or Mr. Norton.

IOW, (D) None of the above. There is _no_ safe DC value that can
be applied to the primary of a transformer. Unless, of course, it's
a transformer that was designed for single-ended class A output. In
that case, it'd be series resistance, or more strictly speaking,
series transconductance.

If this is a test question, then Thaqalain needs to reread the
textbook before re-taking the test. Or ask the teacher what
answer they're trying to extract from the students.

One of the ways test questions are recognizable is by the date.
It's FINALS WEEK! ;-D

Cheers!
Rich

 

[Rich Grise]

On Fri, 10 Jun 2005 16:51:14 -0400, Tom Biasi wrote:

"Rich Grise" <richgrise@example.net> wrote in message
On Tue, 07 Jun 2005 02:07:36 -0700, Winnie Oakbob wrote:

I think this task is too advanced for me, so please, can you help me ?

What would you like to change it to?

Rich,
Sometimes old bulbs or bulbs in a humid or corrosive environment develop a
cupric oxide film between the outer ring and the center terminal. This can
cause a small "leak" in current.
I was aware of what to do when my children and then later, grandchildren
developed a "leak". Perhaps this is why the bulb needs "changing". I think
now-a-days Pampers come in sizes from 25 watt to 150 watt.

LOL!
Thanks!

ObJoke:

How many white guys does it take to change a light bulb?

<spoiler space>
-
-
-
-
-
-
-
<ss>
-
-
-
-
-
-
-
-
<ss>
-
-
-
-
-
-
-
-
</ss>

One.

Cheers!
Rich

 

[Rich Grise]

On Fri, 10 Jun 2005 12:05:46 -0700, John Larkin wrote:

On 10 Jun 2005 07:22:15 -0700, "Thaqalain" <saqlain92110@yahoo.com
wrote:

(1)The number of cycles shown on a scope for a given frequency is
determined by?
*Sweep Frequency
*Volatge Scale
*Ohm's Law


(2)In a triggered scope sweep volume is started by ?
*Sweep frequency
*Trigger Potential
*activated transformer

You've got to be kidding.

Nah, it's finals week.

Cheers!
Rich

 

[ehsjr]

Bob Monsen wrote:

jackbruce9999@yahoo.com wrote:

2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?


The impedance of a set of passive devices is independent of the voltage
across them. It only depends on R, L, C, and f. The fact that there is a
DC component makes no difference.

An inductor will pass DC current as if it were a wire. Only differences
in current cause a voltage across it. A capacitor will not pass DC, so
the DC does not matter. Obviously, a resistor is a resistor, and cares
nothing for ac vs dc.

The key is that the DC is varying - the differences in current you
mentioned. Assuming it is varying at a level where the component
charges and discharges (eg inductor below saturation) there will be
current through and voltage across it. He needs to understand how
each component reacts in his circuit.

Ed

 

[petrus bitbyter]

"padmow" <padmow_69@yahoo.com> schreef in bericht
news:1118439039.287737.144960@g49g2000cwa.googlegroups.com...

Hi.

I'm wondering if there is any match pair for PNP transistor 2SB178.

Also the match pair fo NPN transistor BC108.

is there anyway I can search for the match pair of both transistors by
internet.

Thank you
Padmow

The pnp counterpart for the BC108 is the BC178. Their typenumbers tells them
to be small signal, general purpose silicium transistors. The 2SB178 is a
Japanese type and their numbers has no relations with either European or
American part numbers. FAIK it's an old low power low frequency pnp
germanium transistor ever produced by Matsushita. I guess - just guess -
they were used in the output stages of the two- and sixtransistor
pocketradios at the time.

petrus bitbyter

 

[petrus bitbyter]

<soolun@webtv.net> schreef in bericht
news:1118458492.464910.318940@f14g2000cwb.googlegroups.com...

How can I step down 130 VDC to 12 VDC using an LM 7812. As the 130 VDC
battery pak loses voltage I want to maintain the 12 VDC.

You can't. The LM7812 has a maximum input voltage of 35V. To step down from
130VDC to 12VDC you will need either a discrete build linear- or a switching
(buck) regulator.

petrus bitbyter

 

[Bob Monsen]

wdflannery@aol.com wrote:

Here is a tutorial containing more that you ever wanted to know about

capacitors:

Nothing on double electric layer caps that I can find .

Hmm, I guess it isn't the be all and end all site. Drat.

---
Regards,
Bob Monsen

 

[Lord Garth]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.06.10.18.43.27.778139@example.net...

On Fri, 10 Jun 2005 03:54:20 +0000, Lord Garth wrote:

The glass is completely full - half with water and half with air.

What does that make me? ;-)

Umm, an amphibian? ;-)

 

[Tom Biasi]

<soolun@webtv.net> wrote in message
news:1118463927.184779.195780@g14g2000cwa.googlegroups.com...

OK Thanks. Can you tell me how to connect the circuit using 24 VDC?

Did you try to find the info at all?

Look here: http://www.southwest.com.au/~jfuller/electronics/regulators.htm

 

[John Fields]

On 10 Jun 2005 21:53:54 -0700, wdflannery@aol.com wrote:

Take a look at this:

http://www.elna-america.com/PD?/DZ-N.PDF


Excellent. I didn't find the internal resistance spec for my Panasonic
double layer 1 farad ... but according to the spec for the ELNA the
internal resistance is 10% the usual, and is what .12 ohms which means
the Panasonic should be about an ohm which means my original circuit
should have worked.....

Not necessarily. Because of the low cold resistance of the lamp
filament in series with the cap's one ohm ESR,

http://www.panasonic.com/industrial/components/pdf/ABC0000CE7.pdf

you might not have been able to get enough energy into the filament to
heat it up to incandescence before the charge in the cap was depleted.
It also depends on the thermal time constant of the filament.

Note that the ESR of their 10F offering is <0.1 ohm
---

In any case..... I'd like to get one of these caps if they're cheap.

---
Mouser's got them:

http://www.mouser.com/index.cfm?handler=data.getPcodes&pcode=Elna%2BDouble%2BLayer%2BElectrolytic%2BCapacitors&pcodenumber=55503
---

I did hook mine up the wrong way .......once.... maybe I cooked it.

---
Easy enough to find out.

Charge it up through a resistor and measure the charge current. If
the current into the cap doesn't eventually decay to the specified
leakage current of the cap, then you've hurt it. If it looks good,
then discharge it through the resistor. If T = RC is out of spec,
then you've hurt it.
---

Hmmmmm, in any case, we're getting there.

---
Yup.

--
John Fields
Professional Circuit Designer

 

[Tom Biasi]

<soolun@webtv.net> wrote in message
news:1118493595.887572.124850@g43g2000cwa.googlegroups.com...

Yes, thanks, I had read the info at that website. I was confused
because I had been told to use the LM7812 by someone who I thought was
knowledgeable. I am new to this field.

The 7812 has an "IN" (for up to 30 volts pin 1) and an "OUT" (12 volts
regulated pin 3).
The common (pin 2) or GND is shared between the two.
With a battery you won't need the large input capacitor.
Regards,
Tom

 

[Bob Penoyer]

On Sat, 11 Jun 2005 06:12:09 GMT, Mac <foo@bar.net> wrote:

<snip>

Yes. DC by definition is zero frequency.

Um, no. DC is Direct Current, i.e., current that flows in one
direction. For example, the output from a rectifier is DC but it
certainly isn't "zero frequency."

No, it is NOT DC. Sometimes when speaking casually people call it DC, but
more often it will be called rectified AC.

Rectified AC _is_ DC. Now you might say, But it has a lot of AC stuff
riding on it and that makes it "rectified AC."

Okay, so let's hang a large capacitor across the rectifier's output.
Now, assuming there is some sort of load connected to the rectifier,
there will still be ripple on the load--so there is still some AC
present. Is this still rectified AC? Using your definition, when does
the signal change from rectified AC to DC?

I agree with you that DC stands for Direct Current. But what is the
logical meaning of that? Who knows. The bottom line is that when a
waveform varies with time, it is NOT DC in popular useage.

As long as there is a finite load on the rectifier that I've
described, anything less than infinite capacitance will permit some
ripple to be present. So, since you say "... When a waveform varies
with time, it is NOT DC in popular useage," then the signal will never
become DC.

The simple truth is that a current flowing in only one direction is,
by definition, direct current. It might have AC riding on it, but if
it's direction doesn't change, it's DC.

 

[Fred Abse]

On Fri, 10 Jun 2005 08:59:48 -0700, Bob Eldred wrote:

"Thaqalain" <saqlain92110@yahoo.com> wrote in message
news:1118413335.960660.229320@o13g2000cwo.googlegroups.com...
(1)The number of cycles shown on a scope for a given frequency is
determined by?
*Sweep Frequency
*Volatge Scale
*Ohm's Law


(2)In a triggered scope sweep volume is started by ?
*Sweep frequency
*Trigger Potential
*activated transformer

What the hell is this, A quiz?

More likely multiple choice homework questions.

Damn lazy teacher, if it is

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)