very new to electronics. looking for starting place.

[George Herold]

On Jan 9, 5:56 pm, Michael Black <et...@ncf.ca> wrote:

On Wed, 9 Jan 2013, ianphilipho...@gmail.com wrote:
On Saturday, July 31, 2004 10:02:30 PM UTC-4, Scott Zechman wrote:
Hi all,

I have a very very basic knowedge of electroics. I have a project in mind
that i would like to build but have no idea where to even get started. I
looked over a few posts in this group and they are over my head. Is there a
web site that would have a "getting started" section for someone with my
very limited knowledge? If more details are needed on my project please let
me know. This is a one time project and I am not persuing a career in
electronics, so all the help i can get would be apprecated. If this is the
wrong group to post this in, please parden the intrusion.

thanks,

Scott

This is my first post to a Google group, so hopefully I'm doing this
right and posting in the right place. My interest is in elementary
electronics. I'm a total beginer who will be trying to learn basicaly on
my own. My first tools are a learning kit called Snap Circuits and a
multimeter. Which brings me to my first question. I built a simple
circuit in the kit: It is 2 aa bateries in a battery holder, a switch,
and a small motor. I'm told that a aa battery puts out about 1.5
volts.And when I measure across the batteries I get about 3.5v which
makes sense. But when I throw the switch and turn the motor on then I'm
reading like 9 volts across the motor. That does'nt make sense to me. It
seems voltage should be decreased by the resistance of the motor, not
increased. Can someone explain?

Did you read the original message, that was posted back in 2004, almost 9
years ago?  Did you read the rest of the thread, that might have some
pointers for the beginner?

Did you see my reply to the idiot who replied to this really old thread
via google back in September?
    And you replied to a message from July 31st, 2004.

    The guy is likely not still waiting for an answer (there were a few
    answers back then when it was relevant) and chances are good he's no
    longer a beginner after eight years.  Either he's given up, or he's
    become more capable.

    If a message is older than 30 days, don't respond to it, not via google
    at least and google really needs to fix that problem again.

I still have no idea why people are replying to old posts, though in the
September resurrection, it clearly was so someone could promote their
website.  That doesn't excuse why it's being resurrected again four months
later.

If you have something to say, start a thread.  Even if it's about
something old, don't reply to an old thread, the context is missing except
for people using google (and those of us who see what's happening), the
person who posted originally isnt' likely to still be here

If you actually did a search on something that interested you, and want
more details, don't reply to that thread (the ability to do so is a bug
that google needs to fix), but start a new thread, referencing the old or
quoting some of the old and then asking what you don't understand.

It's just ridiculous to post a reply to an old thread, and ridiculous to
post to an old thread that has no relevance to your question.

     Michael- Hide quoted text -

- Show quoted text -

Hmm, I think Ian was asking a new question. He just didn't know how
to start a new thread. (That's my guess anyway.)

George H.

 

[BeeJ]

Ask your questions any way you can. Most of us will try to interpret.

Your meter is giving you erroneous reading and may either be inaccurate
of needs calibration. Try some other types of cells with know
potential (voltage). See if you can find an adjustment to make your
meter read a little more accurately. It is not all that important to
be accurate but the meter should give good relative readings so you can
see voltage drop or whatever.

As for the motor voltage, remember you are dealing with both DC and AC
whenever you look at any circuit. Some DC circuits oscillate and give
funny reading when measured on the DC meter. Switch to AC on the meter
and see what that reads. Yes, some motor do produce at lot of "noise"
that will make it look funny to a DC measurement. But that noise is
sometimes very useful.

Keep at it and enjoy the world of electronics. I have been doing it
for 40 years and still enjoy fiddling once in a while.

If you look on line you will find many electronics courses that are
totally free and cover more areas than you probably want to know about.
Pick and choose and enjoy.

Learn about basic components first: resistor, capacitor, inductor,
diode transistor etc. You will later learn that a resistor can look
like a capacitor or an inductor in certain circumstances. All part of
the fun.

I used to host junior year electronics major college students for
summer break. They would come to my lab and learn that they were
taught the fundamental theory but knew nothing about the real world.
Find a local electronics store and, as one example, see how many
different types of capacitors there are and learn what each one is used
for and why. Knowing why is what is important because you can apply
that knowledge to other devices.

 

[Tim Wescott]

On Wed, 09 Jan 2013 10:01:20 -0800, Daniel Pitts wrote:

On 1/9/13 9:46 AM, ianphiliphodge@gmail.com wrote:
On Saturday, July 31, 2004 10:02:30 PM UTC-4, Scott Zechman wrote:

<very very old post snipped>

This is my first post to a Google group, so hopefully I'm doing this
right and posting in the right place. My interest is in elementary
electronics. I'm a total beginer who will be trying to learn basicaly
on my own. My first tools are a learning kit called Snap Circuits and a
multimeter. Which brings me to my first question. I built a simple
circuit in the kit: It is 2 aa bateries in a battery holder, a switch,
and a small motor. I'm told that a aa battery puts out about 1.5
volts.And when I measure across the batteries I get about 3.5v which
makes sense. But when I throw the switch and turn the motor on then I'm
reading like 9 volts across the motor. That does'nt make sense to me.
It seems voltage should be decreased by the resistance of the motor,
not increased. Can someone explain?

<useful USENET guidance snipped>

And finally, to perhaps answer your question:

AA batteries usually have at *most* 1.5v, and you'll likely see less
than that. I would have expected something like 2.5v to 2.9v, not 3.5v.

Dry cells usually are pretty close to 1.5V when they're unloaded (i.e.,
when no current is flowing), unless they're very close to being
discharged. With a modern voltmeter I would expect that you'd read
something very close to 3.0V

But you can't count on an "AA Battery" being a dry cell: it may be a NiCd
cell or a NiMH cell, in which case you can expect to see something more
like 1.2-1.25V unloaded.

Voltage isn't "decreased" by a load. Voltage is a potential.

The voltage of a battery _is_ decreased by a load. Different cells have
different characteristics, but they all drop in voltage when you pull
current from them (and almost all of them show more voltage drop per amp
the more discharged they get).

Few DC voltage sources show an increase in potential with current. It's
possible to make one that does it, but such negative terminal impedance
effects are kinda weird.

Also, a DC
motor often contains an inductor (coil or wire), which could affect
voltage. This principle is actually used in DC to DC converters to
increase voltage. To learn more, I suggest reading on first Ohms law,
and then Faraday's law of inductance.

Connecting any load, even an inductive one, to a battery is going to
reduce the average voltage on the battery. The only way to increase the
real average voltage on the battery is to pump current _into_ it with a
source. Raise a dry cell's voltage up to 4.5V/cell, and you can smell
the difference.

I'll be honest, this is outside of my direct experience,

That's obvious.

Hopefully someone more knowledgeable in this group will correct me
if I've mislead you.

You have.

IanPhilip (or whatever your name is):

I can only guess that whatever you're using for a voltmeter is having
problems. A DC motor is going to feed a lot of crap back onto whatever
line is powering it because of the winding inductance that Daniel
mentioned, but a good voltmeter should measure the average voltage, and
that average voltage should go down. It sounds like the voltmeter is
faulty to begin with (because it's measuring 3.5V on two cells), and then
that it is getting confused by the varying voltage on the battery with
the motor running.

What is the brand and model of your multimeter, and how close to new is
it?

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[Tim Wescott]

On Thu, 10 Jan 2013 06:23:43 -0800, George Herold wrote:

On Jan 9, 12:46 pm, ianphilipho...@gmail.com wrote:
On Saturday, July 31, 2004 10:02:30 PM UTC-4, Scott Zechman wrote:
Hi all,

I have a very very basic knowedge of electroics. I have a project in
mind that i would like to build but have no idea where to even get
started. I looked over a few posts in this group and they are over my
head. Is there a web site that would have a "getting started" section
for someone with my very limited knowledge? If more details are
needed on my project please let me know. This is a one time project
and I am not persuing a career in electronics, so all the help i can
get would be apprecated. If this is the wrong group to post this in,
please parden the intrusion.

thanks,

Scott

This is my first post to a Google group, so hopefully I'm doing this
right and posting in the right place. My interest is in elementary
electronics. I'm a total beginer who will be trying to learn basicaly
on my own. My first tools are a learning kit called Snap Circuits and a
multimeter. Which brings me to my first question. I built a simple
circuit in the kit: It is 2 aa bateries in a battery holder, a switch,
and a small motor. I'm told that a aa battery puts out about 1.5
volts.And when I measure across the batteries I get about 3.5v which
makes sense. But when I throw the switch and turn the motor on then I'm
reading like 9 volts across the motor. That does'nt make sense to me.
It seems voltage should be decreased by the resistance of the motor,
not increased. Can someone explain?

Hi Ian, That mostly sounds like a cheap voltmeter. My son has a snap-
circits kit, I can check and see what the voltage wavform looks like
when driving the DC motor. (I don't have much experience with motors.)
You might try looking at the voltage across the batteries.

The voltage waveform when you drive a motor from a source with any sort
of real-world impedance is crappy.

If you consider that a DC brushed motor is a device that automatically
switches an inductive load with mechanical switches many times a second,
this should help you understand why.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[George Herold]

On Jan 10, 5:46 pm, Tim Wescott <t...@seemywebsite.com> wrote:

On Thu, 10 Jan 2013 06:23:43 -0800, George Herold wrote:
On Jan 9, 12:46 pm, ianphilipho...@gmail.com wrote:
On Saturday, July 31, 2004 10:02:30 PM UTC-4, Scott Zechman wrote:
Hi all,

I have a very very basic knowedge of electroics. I have a project in
mind that i would like to build but have no idea where to even get
started. I looked over a few posts in this group and they are over my
head. Is there a web site that would have a "getting started" section
for someone with my very limited knowledge? If more details are
needed on my project please let me know. This is a one time project
and I am not persuing a career in electronics, so all the help i can
get would be apprecated. If this is the wrong group to post this in,
please parden the intrusion.

thanks,

Scott

This is my first post to a Google group, so hopefully I'm doing this
right and posting in the right place. My interest is in elementary
electronics. I'm a total beginer who will be trying to learn basicaly
on my own. My first tools are a learning kit called Snap Circuits and a
multimeter. Which brings me to my first question. I built a simple
circuit in the kit: It is 2 aa bateries in a battery holder, a switch,
and a small motor. I'm told that a aa battery puts out about 1.5
volts.And when I measure across the batteries I get about 3.5v which
makes sense. But when I throw the switch and turn the motor on then I'm
reading like 9 volts across the motor. That does'nt make sense to me.
It seems voltage should be decreased by the resistance of the motor,
not increased. Can someone explain?

Hi Ian,  That mostly sounds like a cheap voltmeter.  My son has a snap-
circits kit, I can check and see what the voltage wavform looks like
when driving the DC motor.  (I don't have much experience with motors..)
You might try looking at the voltage across the batteries.

The voltage waveform when you drive a motor from a source with any sort
of real-world impedance is crappy.

If you consider that a DC brushed motor is a device that automatically
switches an inductive load with mechanical switches many times a second,
this should help you understand why.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com- Hide quoted text -

- Show quoted text -

Thanks Tim, I can imagine all sorts of 'stuff' from a motor.

I hooked up my sons snap circuits. (I forgot my 'scope though.)
But for the OP (or second OP) I measured 3.1 V DC with no motor and
2.6 to 2.8 Volts with the motor. When switch to AC my B&K 391 (true
rms) read 0.1 to 0.5 V. But fast, big spikes will be missed.

George H.

 

[P E Schoen]

wrote in message
news:1d4fb53a-fc14-42fa-8db5-cfec80857e0c@googlegroups.com...

This is my first post to a Google group, so hopefully I'm doing this right
and posting in the right place. My interest is in elementary electronics.
I'm a total beginer who will be trying to learn basicaly on my own. My
first tools are a learning kit called Snap Circuits and a multimeter.

Which brings me to my first question. I built a simple circuit in the kit:
It is 2 aa bateries in a battery holder, a switch, and a small motor. I'm
told that a aa battery puts out about 1.5 volts.And when I measure across
the batteries I get about 3.5v which makes sense. But when I throw the
switch and turn the motor on then I'm reading like 9 volts across the
motor. That does'nt make sense to me. It seems voltage should be decreased
by the resistance of the motor, not increased. Can someone explain?

I have several cheap Harbor Freight meters which are usually pretty good,
but when the battery is low, the internal reference also is low, which makes
the meter read high. That said, it is not unusual for fresh batteries,
especially alkaline, to read higher than 1.5 volts per cell, and may be as
high as 1.65V as you measured:
http://en.wikipedia.org/wiki/Alkaline_battery

Such meters (which usually have AC ranges of 200V and 750V), use a series
diode which responds to the unidirectional peak voltage, calibrated to RMS
based on a sine wave.

The DC motor (brushed PM) will produce spikes which may account for the
higher voltage you read. It could even be inductively coupled to the meter
(which is probably not shielded). A quick and easy fix may be to put a
capacitor across the motor leads.

If you are serious about learning electronics, it would be highly advisable
to get an oscilloscope. You can start with a cheap USB scope which is
probably less than $20, or an older Tek, HP, B&K, Heathkit, or EICO which
might be not much more on eBay, Craig's List, or electronic flea markets
such as Ham festivals. The simpler models are not difficult to fix, and will
present a useful learning experience, although be careful with high voltage
line operated equipment.

And, as others have stated, please start a new thread if you have other
questions.

Good luck!

Paul