Chip with simple program for Toy

[Ban]

cgwiita@ucla.edu wrote:

I'm making a simple electronic-transmission controller for my car, but
I seemed to have run into a problem. The basic idea is to control
three solenoids with a BASIC stamp. I've got everything working like
it should, but I'm having trouble on the output circuits to the
solenoids. Here's the problem: I need to send 12v out of the control
box and to the solenoid (they are grounded internally in the
transmission) with transistor switches. I can't for the life of me
however, figure out a way to send out 12v from the controller,
controlled with the 0-5v of the Stamp pins (doesnt matter if the Stamp
needs to switch high or low). I have the 12v available to me in the
controller, so its really a matter of switching the 12v in the box to
the solenoid 3 feet away. I guess what I'm getting stumped on, is
that with everything I try to setup, theres always a voltage drop
from what I want to switch (the 12v) to the base (0 or 5v, its always
lower...)

Some specs:
solenoids, 10ohm
transistor im using (NTE11)- NPN, Hfe minimum of 230, max current
capacity 5A

Any ideas?

Yes, The transistor needs to be PNP (NTE12), because the solenoids are
grounded. And you need another NPN like 2N3906 to make a level translator.

12V PNP
o-----o------ -----------o
| \ v |
| --- |
| ___ | |
'-|___|-o |
10k | |
.-. |
| |560 |
| |0.5W |
'-' |
| 1N4001 |
INPUT | .---o
___ |/ | |_
o-|___|-o---| NPN - )|
4k7 | |> ^ )|
.-. | | ._)|
| | | '---o
10k| | | |
'-' | ===
| | GND
=== ===
GND GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
View/font fixed

--
ciao Ban
Bordighera, Italy

 

[Larry Brasfield]

"Ban" <bansuri@web.de> wrote in message news:S2hve.2377$h5.132195@news3.tin.it...
[snip]

And you need another NPN like 2N3906 to make a level translator.

The 2N3906 is a PNP transistor.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Steve Banks]

3. How about some sort of foot pump like generator that you can pump the
small lead battery back up, or possibly a lipo directly to save a few
strokes, perhaps even while you are flying.

Not too sure if thats a serious suggestion?

Just tryin to think outside the box. I didn't know if the car was anywhere
nearby or if you were hiking somewhere remote and wanted a more self
sufficient solution. It might not take that many pumps to charge a battery,
lessee if I can take a quick guess:

Lets say your setup can make two pounds of thrust for 600 seconds (10
minutes), or 1200 lb. seconds.

Lets also say you weigh 200lbs.

that means for you to make the same output, you would have to put all your
weight on the pedal for 1200/200 seconds or 6 SECONDS!

Of course there are losses all over the place in this analogy, and the lipo
battery will complain if you charge it in 6 seconds, but it is just a quick
starting point for a guess.

 

[Paul McIntosh]

It'll work just fine, only very slow. Go to Walmart and get a cheap auto
charger. Prolly not more than $20.00.

<junk1@davidbevan.co.uk> wrote in message
news:1119688798.653100.296920@o13g2000cwo.googlegroups.com...

This may sound a bit of a silly question, but currently I use one of
the small 12V 7Ah sealed lead acid batteries to charge my lipos with
(via a lipo charger) - but I only get about 3 charges before the 12V
has dropped too far.

...so the obvious solution is to buy a 12v car battery (about 70Ah).

The question is; will I be able to charge the 12V car battery with the
same charger that I use to charge the 12V sealed lead acid?

As I understand it a car battery is just a lead acid battery? So same
technology and same voltage just higher Ah. Will I blow myself up if I
use the small 12v lead acid charger on the big 12v car batt?


Thanks

David Bevan
http://www.davidbevan.co.uk

 

[Paul McIntosh]

I got a 50A regulated charger that automatically goes to trickle. I think
it cost about $25 at Checker Auto.

"John Miller" <me2@privacy.net> wrote in message
news:d9jhq2$5ge$2@n4vu2.n4vu.com...

Funfly3 wrote:
buy a cheap car charger from a car shop and buy a car battery from Macro
for
Ł17/Ł19 and its got 3 a year guarantee that's what I use

Beware of cheap (unregulated) chargers used routinely. They will boil
your electrolyte, and generate excess hydrogen while they're at it.

--
John Miller
email domain: n4vu.com; username: jsm(@)

 

[Funfly3]

"Tim Auton" <tim.auton@uton.groupSexWithoutTheY> wrote in message
news:fjsqb117sd792e9r32nucki22o3omnap63@4ax.com...

"Funfly3" <dontemailme@ntlworld.com> wrote:
"John Miller" <me2@privacy.net> wrote in message
news:d9jhq2$5ge$2@n4vu2.n4vu.com...
Funfly3 wrote:
buy a cheap car charger from a car shop and buy a car battery from
Macro
for
Ł17/Ł19 and its got 3 a year guarantee that's what I use

Beware of cheap (unregulated) chargers used routinely. They will boil
your electrolyte, and generate excess hydrogen while they're at it.

What's the price of a regulated charger that will charge a car battery
routinely??? a 10AH charger is around Ł45 so a 50AH is going to be a lot
more and the battery has a 3 year warranty all for Ł17 cook it then take
it
back

You're getting Amps and Amp-hours confused. A 10A charger can charge a
100Ah battery.


Tim
--
Don't tell me I'm still on that feckin' island!
No I am not, a decent charger that bulk charges then float charges has a

maximum capacity battery size it can cope with a charger that's designed for
a small battery will not bulk charge a car battery but your right a normal
10 amp charger will charge any battery but it will cook it if left on two
long

 

[Charles Jean]

On Sat, 25 Jun 2005 01:35:44 GMT, Charles Jean
<alchemcj@earthlink.net> wrote:

On 23 Jun 2005 18:30:07 -0700, "davidd31415" <davidd31415@yahoo.com
wrote:

I know you can make a square wave from the sum of sinusoidals, but does
this mean that if you look at a sine-wave that wasn't made by using
sinusoids (perhaps using a switch or an oscillating crystal to turn the
signal on and off) on a spectrum analyzer that you would see all of the
harmonics required to make up the square wave?
___
This post got me to thinking about a related subject. I'm a hobbyist,
and my math is limited to one year of calculus, but I would like to
see if I have a correct conception of what's going on here. I can see
that any periodic function can be put through the Fourier transform to
obtain an infinite series of sin and/or cos terms to completely
describe the original function. This applies to electronic circuits,
musical instruments, vibrational analysis of bridge decks, etc.
So, when one sees a "perfect square wave" on the oscope, it is
actually always a mixture of sine waves of f(fundamental-the frequency
of the square wave as seen on the oscope),3f,5f,7f...... frequencies.
A more complex wave like that produced by a violin string would look
different than either a sine wave or a square wave, because the
mixture of waves producing it are not at the amplitude/frequency
required by the Fourier transform to produce a square wave. If I were
to see what looks like a very low distortion sine wave on the oscope,
I can infer that this is a "true sine" wave, with very little
contribution from any higher harmonics, and not some weird lucky mix
of higher sin/cos frequencies that are significant compared to the
fundamental? Or would the use of a spectrum analyzer be required to be
sure?
For circuit elements like capacitors and inductors, whose reactance
varies with frequency, what happens when dealing with a square wave?
what frequency does one use in the reactance formulas, knowing that
you're dealing with a mixture of them? I would instinctively just put
in the fundamental frequency, but is this right? TIA for clearing any
of this up for me.

___

Thanks for all the great insights you folks provided! They cleared up
some of the fog. I thought John's idea of putting the signal through a
good low-pass filter was a quick, semi-quantitative test for the
presence of significant harmonics was especially neat. Any good
references on how to design/build a decent one? Is it possible to
make one that has a variable cut-off frequency? Or is there a circuit
out there somewhere for a "poor-boy" RF spectrum analyzer?(0.5-30
MHz). Please remember that any thing above elementary calculus leaves
me with puzzled look on my face-this includes differential equations!
Thanks again for the great responses.

Charlie

 

[Fubar of The HillPeople]

I use a Die Hard lawn tractor battery for my electric flying. I charge it
using one of those Battery Tender charger/minders.
Much smaller than a standard car batt with a high capacity.
Cool thing with the tender is you can leave it hooked up all week and it
keeps the battery up without overcharging.
The lawn tractor battery also fits in the bottom of a rolling plastic tool
box I have keeping me self sufficient at the field.

--
Dan
AMA605992
KE6ERB
http://www.fubar1.net
"I've heard the screams of the vegetables..."
Take out the "trash" to reply
<junk1@davidbevan.co.uk> wrote in message
news:1119688798.653100.296920@o13g2000cwo.googlegroups.com...

This may sound a bit of a silly question, but currently I use one of
the small 12V 7Ah sealed lead acid batteries to charge my lipos with
(via a lipo charger) - but I only get about 3 charges before the 12V
has dropped too far.

...so the obvious solution is to buy a 12v car battery (about 70Ah).

The question is; will I be able to charge the 12V car battery with the
same charger that I use to charge the 12V sealed lead acid?

As I understand it a car battery is just a lead acid battery? So same
technology and same voltage just higher Ah. Will I blow myself up if I
use the small 12v lead acid charger on the big 12v car batt?


Thanks

David Bevan
http://www.davidbevan.co.uk

 

[Randy Day]

JennaMyria wrote:

Hello everybody!
My name is Myria and I really don't belong into this group at all, but
I do have a question and searching the web doesn't really get me
anywhere, because I guess I lack some basic understanding of
electronics. I was hoping you could help me.
Simple question: What are resistors actually made of? I mean the inside
material. I know it must be some kind of substance that leads
electricity more slowly (hope I phrase that right), but I am interested
in the actual inside materials.
Reason: My husbands grandfather was a radio/TV repair guy from the 50s
to the late 80s and we inherited a huge collection of, well, different
kinds of resistors (and a couple of capacitators). We couldn't sell
them and I was wondering if I could use them in my craft projects. As I
am working with children, I need to know if there is anything inside
those resistors that is inherently dangerous/poisonous like mercury or
maybe lead. And could it be dangerous by contact alone, or if they
swallowed a resistor? (They are not that age group, but the weirdest
things do happen. In todays suing happy society, you cannot be careful
enough!)
Any info is appreciated. Thanks.
Myria

The older resistors were mostly carbon in a ceramic(?) shell.
The hard shell caps were usually ceramic, too. You may find
a few waxy caps, but I can't recall their composition.
The electrolytic type caps may have some chemicals in them,
but they usually used metal cans as containers.

If the leads have solder on them, the solder likely contains
trace amounts of lead. Not enough to be a concern, I would
think; you would probably have to be more worried about
stomach punctures if one got swallowed.

I've been around components like that for almost as long
as grandpa, and it ain't hurt me none! <blink, blink, twitch, twitch>

HTH

 

[John Popelish]

Charles Jean wrote:

On Sat, 25 Jun 2005 01:35:44 GMT, Charles Jean
alchemcj@earthlink.net> wrote:


On 23 Jun 2005 18:30:07 -0700, "davidd31415" <davidd31415@yahoo.com
wrote:


I know you can make a square wave from the sum of sinusoidals, but does
this mean that if you look at a sine-wave that wasn't made by using
sinusoids (perhaps using a switch or an oscillating crystal to turn the
signal on and off) on a spectrum analyzer that you would see all of the
harmonics required to make up the square wave?

___
This post got me to thinking about a related subject. I'm a hobbyist,
and my math is limited to one year of calculus, but I would like to
see if I have a correct conception of what's going on here. I can see
that any periodic function can be put through the Fourier transform to
obtain an infinite series of sin and/or cos terms to completely
describe the original function. This applies to electronic circuits,
musical instruments, vibrational analysis of bridge decks, etc.
So, when one sees a "perfect square wave" on the oscope, it is
actually always a mixture of sine waves of f(fundamental-the frequency
of the square wave as seen on the oscope),3f,5f,7f...... frequencies.
A more complex wave like that produced by a violin string would look
different than either a sine wave or a square wave, because the
mixture of waves producing it are not at the amplitude/frequency
required by the Fourier transform to produce a square wave. If I were
to see what looks like a very low distortion sine wave on the oscope,
I can infer that this is a "true sine" wave, with very little
contribution from any higher harmonics, and not some weird lucky mix
of higher sin/cos frequencies that are significant compared to the
fundamental? Or would the use of a spectrum analyzer be required to be
sure?
For circuit elements like capacitors and inductors, whose reactance
varies with frequency, what happens when dealing with a square wave?
what frequency does one use in the reactance formulas, knowing that
you're dealing with a mixture of them? I would instinctively just put
in the fundamental frequency, but is this right? TIA for clearing any
of this up for me.


___
Thanks for all the great insights you folks provided! They cleared up
some of the fog. I thought John's idea of putting the signal through a
good low-pass filter was a quick, semi-quantitative test for the
presence of significant harmonics was especially neat. Any good
references on how to design/build a decent one? Is it possible to
make one that has a variable cut-off frequency? Or is there a circuit
out there somewhere for a "poor-boy" RF spectrum analyzer?(0.5-30
MHz). Please remember that any thing above elementary calculus leaves
me with puzzled look on my face-this includes differential equations!
Thanks again for the great responses.

I don't know about .5 to 30 MHz, but if you stay down in the audio
spectrum, you can make some very narrow band pass filters with opamps
that are easily tunable over a wide range while holding fairly fixed
Q. The type that is easiest to adjust is probably a state variable or
bi quad configuration. You can search Google for lots of design info.
Most versions also have a low pass output and some have a high pass
and notch output, so you can do lots of experiments with them. For
instance, with the notch, you can remove the fundamental and see what
other harmonics are left from the wave.

Any of these can be made with a good quad opamp.

http://pdfserv.maxim-ic.com/en/an/AN1762.pdf

 

[Lawrence Oravetz]

James Hanley formulated on Monday :

hi, sorry this post may not appear in the thread it should. I only
have access to google to post, (no newsserver) and google says it's
'unable to retreive the message' (google fails like that sometimes).

I should have given more info.
The device is a KVM Switch (also known as a CPU switch)

meaning: (plug many computer boxes in and then plug in one actual
Keyboard Video(monitor) and Mouse, and you can switch between them -
choosing which computer to access).

The button on the KVM Switch will let me cycle between computers.

The KVM switch is connected to a KVM Extender which boosts 30 meters,
hence the KVM switch is downstairs.
meaning: The system I have, is that the KVM Switch - instead of
plugging directly into a Keyboard monitor and Mouse, is plugged into
a KVM Extender - boosting the signal along a 30 meter cable, into my
room, where my Keyboard monitor and monitor plug in.

I opened up the KVM Switch to have a look. Posts mentioned something
about 4 contacts, I can see them. I could find the correct pair (via
experimenting with a screwdriver or little wire, to see which
activates the switch), and then I could solder one end of a wire to
those 2 contacts, and the other end to an actual switch.

The KVM switch does plug into the mains.

Should I use 30 meters of shielded cable or just normal wire? I have
heard that normal wire may act like an antenna and confuse the kvm.
Though i've also heard that normal wire is fine 'cos it's just a
switch.

I intended to get 24AWG wire - shielded, but the technical sales guy
was convinced that I didn't need shielded, and that shielded would be
harder to solder on. He didn't have the info available to him to tell
me what the AWG of the wire he sold me was, but he said it'll be fine.

thanks

I have a Linksys KVM and double clicking the lefu ctrl key on my
keyboard switches it witgout having ro fish around for the button. If
yours dosn't do that..try the linksys switch.

--
This is an automatic signature of MesNews.
Site : http://www.mesnews.net

 

[Lawrence Oravetz]

Lawrence Oravetz brought next idea :

James Hanley formulated on Monday :
hi, sorry this post may not appear in the thread it should. I only
have access to google to post, (no newsserver) and google says it's
'unable to retreive the message' (google fails like that sometimes).

I should have given more info.
The device is a KVM Switch (also known as a CPU switch)

meaning: (plug many computer boxes in and then plug in one actual
Keyboard Video(monitor) and Mouse, and you can switch between them -
choosing which computer to access).

The button on the KVM Switch will let me cycle between computers.

The KVM switch is connected to a KVM Extender which boosts 30 meters,
hence the KVM switch is downstairs.
meaning: The system I have, is that the KVM Switch - instead of
plugging directly into a Keyboard monitor and Mouse, is plugged into
a KVM Extender - boosting the signal along a 30 meter cable, into my
room, where my Keyboard monitor and monitor plug in.

I opened up the KVM Switch to have a look. Posts mentioned something
about 4 contacts, I can see them. I could find the correct pair (via
experimenting with a screwdriver or little wire, to see which
activates the switch), and then I could solder one end of a wire to
those 2 contacts, and the other end to an actual switch.

The KVM switch does plug into the mains.

Should I use 30 meters of shielded cable or just normal wire? I have
heard that normal wire may act like an antenna and confuse the kvm.
Though i've also heard that normal wire is fine 'cos it's just a
switch.

I intended to get 24AWG wire - shielded, but the technical sales guy
was convinced that I didn't need shielded, and that shielded would be
harder to solder on. He didn't have the info available to him to tell
me what the AWG of the wire he sold me was, but he said it'll be fine.

thanks

I have a Linksys KVM and double clicking the left ctrl key on my keyboard
switches it without having to fish around for the button. If yours dosn't do
that..try the linksys switch.

--
This is an automatic signature of MesNews.
Site : http://www.mesnews.net

 

[Lawrence Oravetz]

Jean-Marie Vaneskahian has brought this to us :

I Need To Trigger a Relay When an LED Lights Up On a Smoke Detector

My goal is to use simple battery operated combination Smoke / Carbon
Monoxide detectors in various parts of my house. I want these battery
operated detectors to trigger a simple contact closure when they
alarm.

I noticed that the detectors have a Red LED that lights up when the
Smoke / Carbon Monoxide detector is triggered. I soldered two small
wires to the PCB on the back of the detector in "parallel" with the
Red LED.

When I connect a voltmeter to the two wires I soldered in "parallel"
with the Red LED and now run from the back of the PCB of the Smoke /
Carbon Monoxide detector I get about +0.001V when nothing happens and
+1.78V when I hit the test button on the Smoke / Carbon Monoxide
detector. By the way, the Smoke / Carbon Monoxide detector runs on a
total of 3 AAA 1.5V batteries.

I have a very basic electronics understanding. One concept that I do
NOT understand is that of "Ground". I do understand how to "Wire"
components though.

My question is this:

How do I take the 2 wires running from the back of the PCB on the
Smoke / Carbon Monoxide detector and generate a basic dry "Contact
Closure" when the detector is triggered?

I am sure this requires transistors, diodes, resistors, reed switches
and a separate battery source, but I have no clue how to connect them
and what types and values to purchase. I buy most of these components
from Radio Shack (Part Numbers Would Be Great!).

Please help me put this together. I really appreciate any wisdom on
this topic. My goal is to protect my family by wiring these battery
operated Smoke / Carbon Monoxide detectors to my home alarm system
that uses contact closures.

Thanks a million in advance,
Jean-Marie Vaneskahian
jean@vaneskahian.com

Doing that modification will void the UL certification of the device
and lets your insurance company off the hook if ever you have a claim.
There are smoke detectors available to interface with your alarm
system.. Look at www.adilink.com

--
This is an automatic signature of MesNews.
Site : http://www.mesnews.net

 

[Larry Brasfield]

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in
message news:l68rb1tsks25l38tpvl8s4ilsagnuavg1m@4ax.com...

On 25 Jun 2005 10:34:26 -0700, cgwiita@ucla.edu wrote:
[snip]
However, I
wouldn't use Larry's KSB834 because I can't get them from Digikey or
the hobbyist suppliers I checked.

Parts you can get are the best kind.

[snip]

Notes: When you apply the 12V to the solenoid, it's probably going to
take some 10s of milliseconds to rise up to the 1A or so you might
expect with the 10 ohms (V/L effect.) Similarly, it's going to also
be even slower to lose its energy, because using the diode will only
allow a small voltage across the inductor during turn-off.

That is a common misconception. When the solenoid having L = Ls
and R = Rs is turned on by applying Vs, its current begins ramping at
Vs/Ls A/S and asymptotically approaches Vs/Rs with an exponential
decay time of Ls/Rs. When the switch is turned off, the current begins
ramping down at (Vs+Vd)/Ls A/S (where Vd is the forward voltage of
the clamp diode, treated as constant) and asymptotically approaches
-Vd/Rs with an exponential decay time of Ls/Rs. The current not only
ramps slightly faster, it is headed for a value on the other side of zero.
So the current decay is definitely faster than the onset.

If such a circuit is slower to release the solenoid than energize it, the
reason is either dissymmetry between pull-in and drop-out voltages,
or an increase in inductance when the moving element is in the
energized position. The clamp diode should only be blamed for
not dropping the voltage as fast as would be possible by applying
a larger reverse voltage to bring the current to zero.

If you doubt this, I urge you to simulate it and study the result.

Finally,
there may be a bit of voltage "ringing"/oscillation at the PNP's
collector as the solenoid's inductance "fights" with the non-linearity
of the diode near the point where the inductor's energy is nearly
spent.

I have looked at lots of diole-clamped solenoids without seeing
such a thing. The circuit will certainly not support oscillation. The
usual appearance is a more rapid drop toward zero Volts across
the diode as its current approaches zero and its impedance goes up.

[snip]
--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Bob Monsen]

Terry Pinnell wrote:

"biltu" <suman_25biltu@yahoo.co.in> wrote:


To day I have make a circuit which is efects timer circuit.this is

stop
any electronics timer lick clock.


Try again - that makes no sense!

Ah, the joys of machine translation.

"All your base are belong to us!"...

http://www.allyourbasearebelongtous.com/

--
Regards,
Bob Monsen

If a little knowledge is dangerous, where is the man who has
so much as to be out of danger?
Thomas Henry Huxley, 1877

 

[Jonathan Kirwan]

On Sat, 25 Jun 2005 20:59:03 -0700, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"Jonathan Kirwan" <jkirwan@easystreet.com> wrote in
message news:l68rb1tsks25l38tpvl8s4ilsagnuavg1m@4ax.com...
On 25 Jun 2005 10:34:26 -0700, cgwiita@ucla.edu wrote:
[snip]
However, I
wouldn't use Larry's KSB834 because I can't get them from Digikey or
the hobbyist suppliers I checked.

Parts you can get are the best kind.

[snip]
Notes: When you apply the 12V to the solenoid, it's probably going to
take some 10s of milliseconds to rise up to the 1A or so you might
expect with the 10 ohms (V/L effect.) Similarly, it's going to also
be even slower to lose its energy, because using the diode will only
allow a small voltage across the inductor during turn-off.

That is a common misconception. When the solenoid having L = Ls
and R = Rs is turned on by applying Vs, its current begins ramping at
Vs/Ls A/S and asymptotically approaches Vs/Rs with an exponential
decay time of Ls/Rs. When the switch is turned off, the current begins
ramping down at (Vs+Vd)/Ls A/S (where Vd is the forward voltage of
the clamp diode, treated as constant) and asymptotically approaches
-Vd/Rs with an exponential decay time of Ls/Rs. The current not only
ramps slightly faster, it is headed for a value on the other side of zero.
So the current decay is definitely faster than the onset.

If such a circuit is slower to release the solenoid than energize it, the
reason is either dissymmetry between pull-in and drop-out voltages,
or an increase in inductance when the moving element is in the
energized position. The clamp diode should only be blamed for
not dropping the voltage as fast as would be possible by applying
a larger reverse voltage to bring the current to zero.

If you doubt this, I urge you to simulate it and study the result.

Finally,
there may be a bit of voltage "ringing"/oscillation at the PNP's
collector as the solenoid's inductance "fights" with the non-linearity
of the diode near the point where the inductor's energy is nearly
spent.

I have looked at lots of diole-clamped solenoids without seeing
such a thing. The circuit will certainly not support oscillation. The
usual appearance is a more rapid drop toward zero Volts across
the diode as its current approaches zero and its impedance goes up.

[snip]

I first admit I'm just a hobbyist on this score. But I didn't need to
simulate it, as I've seen it before. Damped oscillations in the 50kHz
range. I chalked it up to that non-linearity issue. But, of course,
I could be wrong.

So, I just simulated it. And there it is! The simulator seems to see
it, too.

Jon

 

[Jonathan Kirwan]

On Sat, 25 Jun 2005 20:59:03 -0700, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

That is a common misconception. When the solenoid having L = Ls
and R = Rs is turned on by applying Vs, its current begins ramping at
Vs/Ls A/S and asymptotically approaches Vs/Rs with an exponential
decay time of Ls/Rs. When the switch is turned off, the current begins
ramping down at (Vs+Vd)/Ls A/S (where Vd is the forward voltage of
the clamp diode, treated as constant) and asymptotically approaches
-Vd/Rs with an exponential decay time of Ls/Rs. The current not only
ramps slightly faster, it is headed for a value on the other side of zero.
So the current decay is definitely faster than the onset.

If such a circuit is slower to release the solenoid than energize it, the
reason is either dissymmetry between pull-in and drop-out voltages,
or an increase in inductance when the moving element is in the
energized position. The clamp diode should only be blamed for
not dropping the voltage as fast as would be possible by applying
a larger reverse voltage to bring the current to zero.

If you doubt this, I urge you to simulate it and study the result.

I just did, and it shows something I didn't expect but also not what
you say above. The decay time appears to be quite similar to the rise
time. About twice as long, actually, for the decay as for the rise.
But not nearly as much longer as I suspected. I need to look more
into this.

Jon

 

[John Popelish]

davidd31415 wrote:

Ahh yes, glad the context gave that away, *square* indeed.

So how would the sampling rate of an oscilloscope be related to what a
square wave ends up looking like on the scope? Is there a rule of
thumb for the sampling rate of an oscilloscope when sampling square
waves?

At the very least, the scope cannot show a rise time (or any thing
else) less than the time between samples. It can connect two samples
with a straight line. At two samples per square wave, it displays a
triangle.

 

[Funfly3]

"Dr1" <Dr1Driver@aol.com> wrote in message
news:1119788110.957641.288750@g49g2000cwa.googlegroups.com...

but I only get about 3 charges before the 12V has dropped too far.
You need to use a power supply. Using a battery to supply voltage to a
battery charger is a no win situation. It works with field chargers
only because the supply battery is MUCH larger than the battery being
charged, and can be kept peaked by the car's engine.

(about 70Ah).
Good luck finding a car battery that small. They usually come in
ratings of 600Ah or more.
I think on this point your are way of the mark a 600Ah battery is massive

fork lift truck sized, the maximun sized battery fitted to my Vauxhall Astra
is 70Ah

The question is; will I be able to charge the 12V car battery with the
same charger that I use to charge the 12V sealed lead acid?
Yup <giggle> but you may be there for days.

Dr.1

 

[Rheilly Phoull]

One day JennaMyria got dressed and committed to text

Hello everybody!
My name is Myria and I really don't belong into this group at all, but
I do have a question and searching the web doesn't really get me
anywhere, because I guess I lack some basic understanding of
electronics. I was hoping you could help me.
Simple question: What are resistors actually made of? I mean the
inside material. I know it must be some kind of substance that leads
electricity more slowly (hope I phrase that right), but I am
interested in the actual inside materials.
Reason: My husbands grandfather was a radio/TV repair guy from the 50s
to the late 80s and we inherited a huge collection of, well, different
kinds of resistors (and a couple of capacitators). We couldn't sell
them and I was wondering if I could use them in my craft projects. As
I am working with children, I need to know if there is anything inside
those resistors that is inherently dangerous/poisonous like mercury or
maybe lead. And could it be dangerous by contact alone, or if they
swallowed a resistor? (They are not that age group, but the weirdest
things do happen. In todays suing happy society, you cannot be careful
enough!)
Any info is appreciated. Thanks.
Myria

Also remember that such components are cheap as pollies promises these days

If you want to get the kids into electronics spend the money on training,
the components are secondary, also the old ones might also be suspect.

--
Regards ..... Rheilly Phoull