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From: Kari Laine on 16 Mar 2010 16:01
Michael Black wrote:
>
> I had an analog meter when I was 12, and soon it no longer worked, the
> needle having wrapped around the stop too hard. I was careful of any
> later meters, having learned the lesson.
>
> Or, that time when I touched high voltage and when I pulled away my elbow
> slammed into a hard surface enough to hurt, I was careful of high voltage
> after that.
>
> In other words, actually doing mild damage may be a better way of
> preventing accidents than merely warning someone to not do something
> because it might cause an accident.
> Michael
I should have mentioned that I am not totally ignorant about electricity
and electronics. I know the passive components quite well but transistor
has always been difficult to me. I had electronics as hobby when I was a
kid up to something round 16 years old. Then I was in the UNI and
learned something(I am a dropout). Then worked in computer business.
Now I am retired and though that why not...

I have had 220V chocks something round 5 times totally in my lifetime
and they really hurt. Luckily the hart was not stopped. Nowadays I
triple check before touching anything. But naturally accidents could
happen. I am mainly interested the low-voltage electronics (at least now).

The amplifier thing I mentioned turned up nicely.
I got used car audio amplifier for about $90 from auction site in Finland.

Specs:

APA4400G
100W x 4 Channel Amplifier
Maximum Power Output 300 W (75 W x 4)
Continuous Average Power Output 200 W (50 W x 4 into 4 ohms 20Hz-20kHz @
0.04% THD)
Maximum Power Output 700 W (175 W x 4)
Continuous Average Power Output 400 W (100 W x 4 into 4 ohms 20Hz-20kHz
@ 0.02% THD)
Typical 2-ohm Stereo 130 W x 4 @ 0.2% THD
Typical Bridged Power 250 W x 2 @ 0.2% THD
Dynamic Output Control Bass Extender Control 0-12dB
Adjustable 4-Channel 50Hz-200Hz, 24dB/oct. High/Low Pass Crossover
2-Channel Non-Fade Line-Level Output
Mixed-Mode Operation
Bridgeable 4-, 3-, or 2-Channel Operation
Pulse-Width Regulated MOSFET Power Supply

So is this good one or bad?

I have never worked with car amplifiers. But I think it must be single
supply 12V with lot of amperes (I have a lab power supply which probably
can cope). And what is good that according the manual there seems to be
all possible protections for misuse. I only hope the seller is honest...

Well another new tool to play...:-)

By the way these newsgroups are great. I have learned a lot when reading
these groups. I use GigaNews which has retention to year 2003.
Groups about electronics, interesting me contains about
1200000 messages :-)



Best Regards
Kari


--
PIC - ARM - DISPLAYS - RELAYS - MODULES - CONVERTERS - I2C - SPI -
KEYPADS - ACCESSORIES
http://www.byvac.com (I am just a satisfied customer)
From: John Fields on 16 Mar 2010 14:14
On Tue, 16 Mar 2010 19:29:12 +0200, Kari Laine <klaine8(a)gmail.com>
wrote:


>Now when I have you attention you hopefully don't mind a question.
>
>How to find out capacitance and inductance with using function generator
>and scope? Is it easy,not so easy, hard, very hard or impossible?
>I remember seeing this somewhere in the net, but don't find it now.

---
It's pretty easy.

If you have a capacitor and inductor and you know the value of one of
them only, to find the value of the other you can hook up your equipment
like this: (View in Courier)


+-------+
+-----[10K]----+<----[X10 PROBE]---|VERT |
| | | |
| [L] | |
[FUNCTION GEN] | | SCOPE |
| [C] | |
| | | |
+--------------+-------------------|GND |
+-------+

Set your generator to output sine waves and adjust its output amplitude
and the scope's vertical gain control for some convenient display and
then vary the generator frequency until the scope displays a null.

At the very bottom of that null is where the circuit is resonant, and
since we know that, at resonance, capacitive reactance (Xc) equals
inductive reactance (Xl) we can determine the reactance of the component
which we know the value of and then solve for the value of the unknown
component by using that reactance.

For example, let's say we have a 0.1�F capacitor which resonates with an
unknown coil at 10kHz.

In order to determine the reactance of the capacitor we can say:

1 1
Xc = --------- = ---------------------- ~ 159 ohms
2pi f C 6.28 * 1e4Hz * 1e-7F

Now, since we know that the reactance of the coil has to be the same as
the reactance of the cap, we can calculate the inductance like this:


Xl 159R
l = ------- = -------------- = 2.504e-3H ~ 2.1 millihenrys
2pi f 6.28 * 1e4Hz


If you know the value of the inductor, but not the capacitor, you can
find its reactance by rearranging the second equation to:


Xl = 2pi f L


and then find the value of the cap by rearranging the first equation to:

1
C = ----------
2Pi f Xc

Finally, you can check your work with:


1
f = ---------------
2pi sqrt (LC)


so, plugging in the results we got earlier, we'll have:


1
f = ------------------------------- = 10998Hz
6.28 * sqrt (2.1e-3H * 1e-7F)


About 10% high because there are rounding errors in there, but you get
the picture, yes?


Another way is to use a resistor of a known value in series with the
unknown cap or coil:


+-------+
+-----[10K]----+<----[X10 PROBE]---|VERT |
| | | |
| | | |
[FUNCTION GEN] [DUT] | SCOPE |
| | | |
| | | |
+--------------+-------------------|GND |
+-------+

I've gotta go do some chores, but I want to get this off instead of
waiting until later to send the whole thing, so I'll finish it when I'm
done...

JF
From: Hammy on 16 Mar 2010 15:36
On Tue, 16 Mar 2010 19:29:12 +0200, Kari Laine <klaine8(a)gmail.com>
wrote:


>Now when I have you attention you hopefully don't mind a question.
>
>How to find out capacitance and inductance with using function generator
>and scope? Is it easy,not so easy, hard, very hard or impossible?
>I remember seeing this somewhere in the net, but don't find it now.
>
>
>Best Regards
>Kari
>

Johns giveing you a nice detailed instruction but I see from your sig
that you are at least familiar with PIC's so you could build your own.

Here is a pretty good one.

http://ironbark.bendigo.latrobe.edu.au/~rice/lc/
From: Ron M. on 16 Mar 2010 19:35
On Mar 16, 1:26 pm, Michael Black <et...(a)ncf.ca> wrote:
> On Tue, 16 Mar 2010, Kari Laine wrote:
> > John Fields wrote:
> >> On Tue, 16 Mar 2010 13:23:14 +0200, Kari Laine <klai...(a)gmail.com>
> >> wrote:
>
> >> ---
> >> I suspect a couple of hits to the pocketbook will shorten the learning
> >> curve and lengthen the attention span appreciably.
> >> ---
> > What you mean with this...Do you mean I should buy some books or
> > something? If so ISBN is?
>
> I had an analog meter when I was 12, and soon it no longer worked, the
> needle having wrapped around the stop too hard.  I was careful of any
> later meters, having learned the lesson.
>
> Or, that time when I touched high voltage and when I pulled away my elbow
> slammed into a hard surface enough to hurt, I was careful of high voltage
> after that.
>
> In other words, actually doing mild damage may be a better way of
> preventing accidents than merely warning someone to not do something
> because it might cause an accident.
>     Michael
>
>
How about 15 watts VHF right into the palm of your hand. That is an
attention getter. Won't touch that again.
>
> > My attention span is very bad indeed, it has always been. Nowadays they
> > even have a diagnosis for it...
>
> >>> Then I would need a power supply for +/- 28 DC for these amplifiers.
> >>> It is not clear to me what the maximum amperage should be - anyone?
>
> >> ---
> >> According to the specifications, 4 amperes.
> > Thanks did not notice it.
>
> > Best Regards
> > Kari- Hide quoted text -
>
> - Show quoted text -

From: Kari Laine on 17 Mar 2010 04:15
John Fields wrote:
> On Tue, 16 Mar 2010 19:29:12 +0200, Kari Laine <klaine8(a)gmail.com>
> wrote:
>
>
>> Now when I have you attention you hopefully don't mind a question.
>>
>> How to find out capacitance and inductance with using function generator
>> and scope? Is it easy,not so easy, hard, very hard or impossible?
>> I remember seeing this somewhere in the net, but don't find it now.
>
> ---
> It's pretty easy.

Thank you! Even I understood. If you have time the second method would
be interesting.

Best Regards
Kari
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