anand,

I hope that I have clarified your point.

So it sounds like there is no conversion between ASCII
and Modbus, it's apples and oranges time.

Jim

--- In Electronics_101@y..., iman hermansyah <iman_hermansyah@y...>
wrote:

Hi Gusys,

Hi Imam,
My name is Anand Ahuja. As you have come to know by now, ASCII is
representation of various characters, including space, special and
control characters, in memory of computers.
Modbus is a communication protocol which works on RS485 bus. RS485
bus has different other protocols also which are used for
communication. RS485 bus is a two wire bus which is used in
industrial control for communication between various devices like a
PLC, temp. controller, electrical power monitor, AC or DC Drive, HMI
(Human Machine Interface).
The Modbus protocol uses ASCII characters for transfer of data between
devices. Besides, a protocol has other parameters like no. of bits,
parity, stop bits, baud rate, error checking and correction. Profibus
(from Siemens), Devicenet and Controlnet (from Allen Bradley) are
among the other protocols that are implemented on the same RS485 bus.
However, all of them cannot be implemented on the same bus. All the
devices sitting on the RS485 bus can be configured to communicate on
the same protocol. Each protocol has certain variations like no. of
bytes sent per packet, error checking, transmission speed,
master/slave or peer-to-peer mode, etc.,.

I hope that I have clarified your point.

Anand Ahuja

Iam a nandew comer in electronic world...
Could somebody teach me what is differencies between
ASCII text and Modbus,for inter-device communication.
Is there an interface for these?

Thank's

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Hello all,
I'm trying to build an electronic flute and need a
way to create each note from a source tone.
I'm using a voice record and playback IC (ISD1420P)to play
a looping tone as the source.
I think I need a frequency divider but not sure, if I do
how do I set one?
Is there another way about it?
I'm still a beginer in electronics, any help would be appreciated.
Thanks,
Alan

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开云体育

开云体育

>i need a circuit which convert my monitor into tv receiver.
>i will be very thankfull.

iman,

I just red the instruction,Modbus is a protocol for
data tranfering.

So is ASCII, can you say something about where or why
it is used instead of ASCII?

which created by Modicon. Presently i've problem to
establish communication between 2 communication which
different protocol,one is ASCII and the other is
modbus.FYI i use RS-485 for this comm.
Anyway i'm getting clear in ASCII code.

The first thing you could do is locate a table for both and compare the
two. If you had two tables in memory, one ASCII, the other Modbus.
Another table would contain the jump addresses to the code to which
you are converting. Say you're converting ASCII to ModBus. The first
character comes along, and pointers point to ASCII and the jump table.
The convert program compares each the incoming ASCII character
with one in the ASCII table. If no match is found both pointers are
incremented. This repeats until a match is found, at which time the
second pointer should be pointing to the correct jump table value
enabling the program to load the alternate code into the accumulator
(or a variable in high level language. ) and send it wherever it is
supposed to go. Then pointers are resent and the next character
retrieved, etc.

Jim

Thank's Jim,

I just red the instruction,Modbus is a protocol for
data tranfering. It's a standard protocol comunication
which created by Modicon.Presently i've problem to
establish communication between 2 communication which
different protocol,one is ASCII and the other is
modbus.FYI i use RS-485 for this comm.
Anyway i'm getting clear in ASCII code.

Iman.
--- Jim Purcell <jpurcell@...> wrote:

iman,

Could somebody teach me what is differencies

between

ASCII text and Modbus,for inter-device

communication.

Now quite frankly I haven't heard of Modbus. I can
tell you
that ASCII, American Standard Code for Information
Interchange,
is simply a numeric code for letters, numbers, a few
special
characters and some control characters. ASCII is
widely used,
probably the standard, in the US. I would think that
it may be
the standard for the world now, to have to convert
among
various codes in international message handling
would seem
an herculean task. When comparing communication
codes
there are a number of considerations. Back when this
sort
of communication was far less reliable the EBCDIC
code
was sometimes used because it was more easily error
checked. I have never worked in an environment where
EBCDIC was in use.

Other considerations might be, what kind of
information
is being transmitted. I don't know what is done to
ASCII
when special characters are required, ones that look
strange to us who are accustomed only to English.

I haven't answered your question, but at least you
know that
your message was received. This forum seems to have
people
of widely varied skills and knowledge, I'm certain
that someone
will be able to help you. It might help if you told
us the context
in which you know about the Modbus code.

Is there an interface for these?

If the only difference between two code is the
numerical values
conversion is quite simple. A look up table is often
used, the
position in the table for one code is matched with
the position
in the other table. A program has two pointers, one
pointed
at the start of each table. The first table is
searched
while incrementing both pointers until a match is
found.
Then the value pointed to by the second pointer is
the
converted character. There may be some programmers
in the group who know a more sophisticated
conversion
scheme. I've never needed one.

Jim

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--- In Electronics_101@y..., Jim Purcell <jpurcell@w...> wrote:

I clearly read that Mark didn't mean a heatsinked fuse,
but a common fuse IN CONTACT with a heatsink (let's say,
for example, the secondary fuses of a power supply's
tranny in contact with the rectifiers heatsink).

Unless you meant it was in contact accidentally it would

Yes, I meant accidentally, sorry for the missunderstanding.

P.S. your name if I don't miss my guess is the same as
Marconi's, I have always wondered how that name was
pronounced. I'm guessing that phonetically it would be
spelled, 'gee-er-mo' but that's how I would guess the
Spanish pronunciation might be. I know even less Italian
than Spanish. :-)

About the spanish pronunciation, you are 95% correct, it goes like
gui (like "gi" in "give") ller (like "Jerr" in "Jerry") mo (like "mo"
in "moth"). Also, Marconi's first name was Guglielmo, wich has the
very same root as Guillermo and William.

Saludos,

Guillermo.

Guillermo,

it's stored in vacuum capacitors.

That's a good one! I would be very grateful if you tell me the

Have to get it from someone besides me. I'm neither a physicist,
nor an engineer, although I challenge an engineer to explain it. :-)

Jim

what I can't figure out is where
it's stored in vacuum capacitors.

That's a good one! I would be very grateful if you tell me the
answer.

Guillermo.

Can anyone answer my original question - Why are fuses not rated in
units of power?

As fuses are used as overcurrent protection devices, the relevant
factor here is the CURRENT that the fuse will carry before melting.
Power is somewhat irrelevant here, as it would be an indirect way to
tell you the important parameter, the current capacity.

I cannot recall anyone designing a circuit saying "then, I want the
fuse to blow while it dissipates 10W or above", but " I want the the
fuse to blow while 10A or above go through this path".

Also, power alone is useless, you need also the resistance of the
fuse to calculate the current capacity, or the voltage drop across
the fuse.


Guillermo.

开云体育

d,

suggested bypass transistors as a method for limiting current at the input
to LM3xx and LM78xx voltage regulators.

First off, maybe you mean a pass transistor. This approach involves using the
regulator to establish the output voltage at the base of a power transistor,
then the power supply output is taken from the collector. The unregulated DC is
applied to the collector. So the transistor isn't a special device except that
it is designed to operate at higher current than the regulator. In that sense
the input current to the regulator doesn't need to be large because the
transistor passes the current to the load, not the regulator. Of course the
actual output voltage will be the regulator voltage minus about 0.7 V, the
normal BE drop on a silicon transistor. Some circuits use more complex
regulators that use the actual output voltage to control the base reference
voltage.

Jim

What are bypass transistors and how do they work? What types are good for
this?

-Mike

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Your use of Yahoo! Groups is subject to

Back in August I posted a question about building a power supply and someone suggested bypass transistors as a method for limiting current at the input to LM3xx and LM78xx voltage regulators.

What are bypass transistors and how do they work? What types are good for this?

-Mike




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Here's an idea:

Buy a new VCR.

Seriously, these things are cheap now. I've seen them for as little as $50. If you were good at electronics and had access to tools and parts I could see fixing it yourself, but there is no justification in paying someone to fix such a low cost item.

-Mike


Victor Lee <emaillee@...>:

We are Veron and Vic , siblings from Malaysia.
Nice to meet you.

We have a fully automatic Toshiba VCR , which is 4 years old.

recently, I insert an old tape[ which is my favourite tape ] into the
VCR.

It automatically jumped out after I heard the processing of the clever
mechanism inside seems like the electronics inside do not let it go on ,

maybe it is problematic tape.

But, I am too eager to watch to series show, I regreted to have inserted
it a few times inside again.

Finally, The tape stucks inside !!! I have to remove the cover in order
to cut out the tape twirling onto the rollers etc.

I thought everything will turn to normal after I recap the cover and put
everything back.

But, It no longer works. Tapes inserted will not wind automatically onto
the rollers , it just stops there, So , I have to eject it .

What is wrong ?

I do not trust my technicians here because, I had it repaired once
before. The technician here just left it for 2 months and, finally they
say
that they cannot repair !!!!!
I was charged for the service. Then, the technician sent it to the
toshiba technician.
I was told that IC chip inside was burnt out.

So, the total repair time took 3 months, and I was charged twice. and it
is not cheap for the IC chip.

Please help.

thank you ,

veron and vic

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Hi folks,

I just started a Yahoo!Group for us techies in the Portland,OR area.
Maybe we can get a group going and try setting up some meetings so we
can show our project, help each other out and stuff. I just started
the group today, so of course there's no messages there yet. But I
hope that will change.



-Mounir

Sure, you'll need a few things to get started:

1) A microcontroller (from Digikey, Jameco, etc.)
2) The hardware to program the microcontroller (many designs exist online that can be built for less than $10)
3) The software to program the microcontroller (often comes with the HW)
4) The development software to create the program that you'll load into the microcontroller. If you're going to program Microchip's PICs, you can get their development environment free.

Might I suggest a book I have suggested previously: "PIC Microcontroller Project Book" by John Iovine. It looks like a pretty good beginner book.

So what's your project idea?

-Mike



charlexus@...:

i want to make a project using a microprocessor or a microcontroller.
would you help me with an idea...

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Jim,

The software to program the PIC or the program itself?

Oh, so the device is always a heartbeat away from it's father. :-)
Interesting idea. I should think then that most programs are far
smaller than the development system on the chip.

I'm not sure what you meant by this, but, once programmed, the PIC can be placed in its own circuit to perform its duties - its program stays in its EEPROM (or EPROM) and will start running once power is applied. Most PICs can even be programmed in-circuit.

Assembly, OK, I think I keep getting the Stamp and the Pic confused.
I was thinking BASIC. And of course the final program has to be binary
rather than hex doesn't it. Does a HEX file have any meaning in this
case?

Stamps actually use surface-mount PICs. They also have a BASIC interpreter on board. And they run slower and are more expensive than PICs.

PICs can indeed be programmed in BASIC (PICbasic) - if you want to pay for it - although most people I've run into who work with them just program in assembly (the software is free!).

The hex file is generated from the development software. I'm not sure if this is a standard, but it sure is the common practice. The programmer then takes it, converts it to op-code (binary), and writes it to the PIC.

It's pretty seemless, though. My setup works like this:

1) I write the program in MPLAB (Microchip's dev. software).
2) I compile it, which creates a hex file (after I've eliminated bugs).
3) I run the programming software, which takes the hex file, converts it to binary and writes it to the PIC, which is sitting in the programmer connected to the parallel port of my PC.
4) I take the PIC out of the programmer and put it on my breadboard for experimenting, or into the final circuit.

When power is applied to the PIC it does whatever the program is supposed to do.

If I wanted to I could even program the PIC without removing it from its circuit. This makes it very easy to update.

-Mike



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Hmmmm. Somehow the problem solved itself. So, it must've been in the
software somehow. I thought I blew a hardware connection. But,
maybe you can explain the mic in the computer and what happens when
you mistake your output jacks for input jacks...

I was wanting to play sound out of my laptop through a couple of
speakers. But, I connected the speakers into the mic jack instead of
the sound out jack. My mic has'nt worked since. ?

Try this:

+
|
R
|
*---||--------- Opamp Input
|
R
|
-

Did you understand that ? I sure didn't :). The point with the
negative voltage is to allow the audio signal to swing both ways Now
if you're able to put the audio signal to swing around 6V instead of
0V, then you can just use the 12V car battery without a negative
voltage.

Use for example two 1K resistors. One between Vcc and opamp input,
and one between opamp input and GND. Connect the opamp input VIA A
CAPACITOR to the audio signal source.

I think that should work

Mounir
--- In Electronics_101@y..., a_w_abate@y... wrote:

I was fairly interested in electronics when I was in high school.

To

the point where I built several kits including a COSMAC Elf 1802
computer. However, I strayed from the hobby over the years but am
slowly returning. Now I am challenged by OpAmps and negative

voltage.

I do not understand how to generate a negative voltage (for
differential inputs) from one power supply such as a car battery. I
am trying to build a small headphone amplifier and am just coming

up

with noisy audio. I believe this is because I am not apply the
negative voltage correctly. help!