--- In Electronics_101@y..., "d nixon" <dnixon9@h...> wrote:

The key is the special signals that are recorded on cd.

No, the key is how much money some fool is willing to pay for such

a device.

Package it with a new diet and you've got yourself a money-maker.

-Mike

It really is very involved. And the purveyor of the study spends a
great deal of time on the phone giving technical support. I don't
think this has anything to do with making money. The device itself is
simple enough. The signals, however, would require something like
Wavewriter to duplicate. A great deal of info can be found on this
subject by searching the archives of the mind-l yahoo group. The
patent for some of the prototypical technology can be found in the
files section under "Thomas patent" and some representative waveforms
are in the photos section. It really does seem to produce some
remarkable effects. I myself was the fiercest critic of the study but
will be ordering mine in a few weeks. This is the telegraph of brain-
electronic interfaces that will lead to a cable modem, someday.

Sic Luceat Lux

Xenoticus

You will probably find answers to your questions about the Microchip
PIC family of micro-controllers on one of the _many_ PIC discussion
groups or other micro-controller discussion groups. Though it is an
interesting topic here it may be more productive there. I'll bet a
lot of people on this list are also on one or more uC lists.



--- In Electronics_101@y..., "Mounir Shita" <mshita@c...> wrote:

If I understood Microchip right, then there is no further

development

of the 17-family, right?

Must agree, 18 is way better than 17. Hopefully soon they'll get

all

their parts out in flash versions. Have you thought about using the
dsPIC, when it comes out, to something ? I'm very excited about

that

part. Price wise, its very close to the PIC18-family. However, its

16

bit and much faster.

Mounir

If I understood Microchip right, then there is no further development
of the 17-family, right?

Must agree, 18 is way better than 17. Hopefully soon they'll get all
their parts out in flash versions. Have you thought about using the
dsPIC, when it comes out, to something ? I'm very excited about that
part. Price wise, its very close to the PIC18-family. However, its 16
bit and much faster.

Mounir


--- In Electronics_101@y..., aseesf4@a... wrote:

How do you compare the PIC17 family to the PIC18 family? I only

used PIC17

once before PIC18 was introduced. But on my current project I was

comparing

PIC17 and PIC18. I honestly couldn't find any reason why Microchip

still made

the PIC17 series. PIC18 is way better and about the same price.

Am I missing something ? Do you have good experience with PIC17?


When we started this project I had intended to use separate PWM

outputs to

each of the three phases of the motor, therefore I needed three PWM

outputs.

The PIC17C756A was the best choice available with 3 PWM outputs.

Later,

changes were made to the motor and controller and I no longer

needed separate

PWM outputs. If I had known this earlier I would have used a PIC18

series

chip.

The PIC17 series was the next logical step for Microchip to take at

the time

they developed it. I believe it was just a step along the way to

the PIC18.

Microchip still supports this family, even though the PIC18 is a

much better

choice if you need more power than the PIC16 which is much cheaper,

because

of their policy of whenever possible always supporting past lines.

They do

this to prove to their potential customers that they will not be

hung out to

dry because of discontinued or obsoleted parts.

I repair very high power-voltage equipment and so far I've not used gloves
before. What i did was to use a ground stick and make sure I discharge the
capacitance voltages that were "trapped" before I actually use my hands to
service the equipment.

However at times, we still need to "check" the equiments while the equipment
is running, thats where the danger lies. Obviously an insulated mat won't
help much.

After reading your thread, I guess one just have to be extra careful when
dealing with these high power-voltages equipments. Once is enough!

I take my last message back. I just read the top of it and it looked
like my post. Thought something went wrong somewhere :)

Sorry.....................

Mounir


--- In Electronics_101@y..., aseesf4@a... wrote:

How do you compare the PIC17 family to the PIC18 family? I only

used PIC17

once before PIC18 was introduced. But on my current project I was

comparing

PIC17 and PIC18. I honestly couldn't find any reason why Microchip

still made

the PIC17 series. PIC18 is way better and about the same price.

Am I missing something ? Do you have good experience with PIC17?


When we started this project I had intended to use separate PWM

outputs to

each of the three phases of the motor, therefore I needed three PWM

outputs.

The PIC17C756A was the best choice available with 3 PWM outputs.

Later,

changes were made to the motor and controller and I no longer

needed separate

PWM outputs. If I had known this earlier I would have used a PIC18

series

chip.

The PIC17 series was the next logical step for Microchip to take at

the time

they developed it. I believe it was just a step along the way to

the PIC18.

Microchip still supports this family, even though the PIC18 is a

much better

choice if you need more power than the PIC16 which is much cheaper,

because

of their policy of whenever possible always supporting past lines.

They do

this to prove to their potential customers that they will not be

hung out to

dry because of discontinued or obsoleted parts.

Something got screwed up here. The message below was sent by me,
Mounir and not aseesf4@....

Mounir

--- In Electronics_101@y..., aseesf4@a... wrote:

How do you compare the PIC17 family to the PIC18 family? I only

used PIC17

once before PIC18 was introduced. But on my current project I was

comparing

PIC17 and PIC18. I honestly couldn't find any reason why Microchip

still made

the PIC17 series. PIC18 is way better and about the same price.

Am I missing something ? Do you have good experience with PIC17?


When we started this project I had intended to use separate PWM

outputs to

each of the three phases of the motor, therefore I needed three PWM

outputs.

The PIC17C756A was the best choice available with 3 PWM outputs.

Later,

changes were made to the motor and controller and I no longer

needed separate

PWM outputs. If I had known this earlier I would have used a PIC18

series

chip.

The PIC17 series was the next logical step for Microchip to take at

the time

they developed it. I believe it was just a step along the way to

the PIC18.

Microchip still supports this family, even though the PIC18 is a

much better

choice if you need more power than the PIC16 which is much cheaper,

because

of their policy of whenever possible always supporting past lines.

They do

this to prove to their potential customers that they will not be

hung out to

dry because of discontinued or obsoleted parts.

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We had a good teacher and he really did teach us to do most of the
work in our heads. Maybe he was able to give us all that 'intuitive'
feel that it took to do it fast. I can't do it anymore though. I
really haven't needed to do transistor circuit analysis in a long
time. The last time I used DPI was to nomalized a thermistor circuit
for a lead acid battery charger.

Do you remember the name or author of the text that you used? We
only had a series of notes from the instructor.

There is a method called Driving Point Impedance Analysis that

makes

AC analysis easier. Most of the analysis can be done in your

head.

Whoa! Its easy, but not that easy! :-) This is the method we

used to follow in school.

Rama

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See, I told you the math wasn't that hard.

Yeah - the math is never hard :-)

There is a method called Driving Point Impedance Analysis that makes
AC analysis easier.? Most of the analysis can be done in your head.

?

Whoa! Its easy, but not? that easy! :-) This is the method we used to follow in school.

Rama

--- In Electronics_101@y..., "G Ramasubramani" <grama@a...> wrote:
> Actually, if you work with the AC picture of the circuit, replacing
the transistor in the circuit with the equivalent current and voltage
sources, it is as simple as applying Kirchoffs laws.
>

A precise explanation, Paul.
Thanks,
SUNAN

See, I told you the math wasn't that hard.

There is a method called Driving Point Impedance Analysis that makes
AC analysis easier. Most of the analysis can be done in your head.

--- In Electronics_101@y..., "G Ramasubramani" <grama@a...> wrote:

Actually, if you work with the AC picture of the circuit, replacing

the transistor in the circuit with the equivalent current and voltage
sources, it is as simple as applying Kirchoffs laws.

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How about sensitivity analysis! Arrggg! "Kenneth, what is the Early
voltage?!"


--- In Electronics_101@y..., "G Ramasubramani" <grama@a...> wrote:

(P.S. the math isn't really all that bad >> for a single

transistor)

Even when you start applying negative feedback? :-)

Rama

Rama,

>>(P.S. the math isn't really all that bad >> for a single transistor)?Even when you start applying negative feedback? :-)

By the time you get that far you have also had to contend with the effect of following stages. The gain of a stage is usually never as good ad the beta, i.e. current gain. Stage gain is roughly equivalent to? Rc || R load divided by the emitter AC resistance. (the || is shorthand for in parallel with).? In most cases you can ignore the r(sub)E unless the emitter R is low or you need a more accurate figure.

Jim

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Yes, excellent advice. Here are a couple of points for general
knowledge.

The gain of the transistor (beta) is the given in the data sheets as
either beta or hfe. That gain is measured in the linear operating
region or in other words where it is highest. Beta is collector
current divided by base current. As the transistor nears saturation
the beta is greatly reduced. For switching applications where the
transistor must be on "hard" a general rule is that the beta is
reduced by a factor of 10. You can get away with a factor of 5 in
low power applications, or at least I have done it.

Saturation can be measured. When the relay is energized, measure the
emitter to collector voltage. It should be near 0.1V or so depending
on the transistor. If it is much higher, then too much power is
dissipated in the transistor. The power should be dissipated in the
load not the switching element. To resolve this, increase the base
current or select a transistor with better specifications.

Now you can see why FETs are often used for switching applications.
There is no current flow into the gate. FETs have there own set of
problems but that's another topic. For your particular application,
a logic level FET should work very well.

Protect the transistor. In relay applications, be sure to put a
reversed diode across the relay coil and very close to the relay.
The diode is standard practice on all relay circuits and is even
included in some relays. That is one reason why relay coils often
have a (+) and (-) mark on the coil leads. When the relay is shut
off the coil field collapses and creates an inductive 'kick' that can
reach hundreds of volts. That kick can break down the transistor
juctions causing a fast or slow failure. It may work alright today
but...

Hope that helps.
(P.S. the math isn't really all that bad for a single transistor)

--- In Electronics_101@y..., mehdi Rostami <mrostamy@y...> wrote:

Hi Jonathan,
I was looking at the specifications of the BF469 and well, the

transistor is not really intended for use as a switch, although I
suppose any transistor be used as a switch as long as some care is
taken. It happens that you have not told us what is the relays
minimum operating current, at its specified voltage drive. The
transistor you used has a peak Colector current of 100mA. I would
suggest That you use a more common but more robust transistor, like a
TIP31 or even a 2N2222, the latter dealing well with 300mA (500mA
limit), and being very suitable for switching applications as well as
high frequency switching, PWM, etc. Please bear in mind that the
transistors with BF prefix are usually signal transistors for audio
and video. In this case you are using a "high voltage NPN intended
for class B video applications"

One other question, why did you put the realy at the emitter? The

most usual and correct topology is the emmiter connected to ground
and the relay in the colector. I think that this is the first
modifiction to do...put the relay in the collector!

In order to saturate a transistor, you need enough current, so it

is not directly a question of the voltage aplied to the base,
referred to the emmiter. With a voltage of 0.6V between the base and
emitter a transistor would start to turn on, so 6 Volt is more that
enough to get the transistor saturated. If you are really interested
in the maths behind the transistor design it?s really very easy, but
you would have to know the relays impedance, its operating voltage,
the transistors saturation VCE, and of course the voltages available.

Good luck and keep us informed!


Jonathan Luthje <jluthje@p...> wrote: Hi Guys,
I see there a few knowledgeable people getting around the

group, so I'm

hoping one or more of you can help me. I am trying to use a

transistor

(BF469) to drive a relay using an MPU - the problem being it

doesn't seem to

be switching. It would appear to me that the transistor isn't

saturating.

I have 2 power rails with a common ground (+6v regulated & +12v

unreg) - I

am applying 6v to the base via a 1.6k resistor, collector is

getting 12v

unreg., emitter is (of course) attached to the relay coil with a

diode

across it - the other end of the coil going to ground. If I short

out the

1.6k resistor, the relay "flutters" very weakly - indicating to me

that the

12v coil is only receiving 6v. If I short out Base/Collector it

switches

hard on.

Can I saturate an NPN trannie w/6v on base to drive a 12V

collector/emitter?

Do I need to apply a bias resistor somewhere in there?

Thanks in advance for any help,


Regards,


J0n





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