PIC - Recommendation for a first time user

Thank you everyone for your input to my earlier thread for my need of
a one chip solution that directed my application to using a PIC.

As a new PIC learner can you give me a PIC choice & part # (kit) that
has the flexibility I need for my application? Also a good webpage for
PIC projects would also be helpful. I have several years of old
experience, covered in cob webs, in the use of 8080 Assembly & Basic
programming languages which hopefully will allow me to grasp the PIC
language quickly.

Webpage link to my application need:

http://www.oldtemecula.com/theremin/tan/index.htm


My need in the ideal PIC (AFC) application:

A PIC samples its Input every 10 minutes from a manually activated &
conditioned Update Pulse. The Input is sampled for a 200 Hz frequency
in a 1/2 sec timing window and compared to 100. It has a possible
count value above or below a 100.

PIC INPUT = 1 Volt p-p AC @ 50 Hz - 300 Hz

PIC OUPUT = 5v to 6v DC @ 1 ma with a resolution of 100 increments.

PIC features:
OP Amp
F-V
ADC
Latch
DAC

* * *
Below is a first attempt not knowing any PIC language using some past
terms for crude logic in my Automatic Frequency Control. I will refine
the logic when I get a specific PIC for my application.

Dim vInput_count %, vOutput_V%

vOutput_V = 5.5v
PIC_Output = vOutput_V ' set PIC Output to 5.5 volts


label1:

If Terminate_ Pressed then End

vInput_count = PIC_Input '1/2 second PIC frequency Input sample"

If vInput_count > 100 then
vOutput_V = vOutput_V - .01 'minus .01 volts from PIC Output
'lowers the frequency at the PIC Input.
PIC_Output = vOutput_V

Goto label1

Else

If vInput_count < 100 then
vOutput_v = vOutput_V + .01 'adding .01 volts to Output raises
'the frequency at the PIC Input.

PIC_Output = vOutput_V

Goto label1

End if 'Program proceeds when Input_count = 100


Do until Update pressed 'Wait for 10 minute signal to Update
'sample at the PIC Input.
Loop

Goto Label1


End


* * * *

Christopher

Temecula CA.USA
http://www.oldtemecula.com

 

[RD]

In article <djtib45cp7cbkgev5sqv7et4o6s6a1g671@4ax.com>,
christopher@REMOVEoldtemecula.com says...

[snip]

PIC INPUT = 1 Volt p-p AC @ 50 Hz - 300 Hz

PIC OUPUT = 5v to 6v DC @ 1 ma with a resolution of 100 increments.

I don't have any direct experience with the
dsPIC's (the ones with the built-in DAC
output), but I'm fairly certain they provide
a steady output voltage level between 0 and 5
volts.

You'd have to provide a DC offset somehow to
reach your 5-6 volt range.

On the plus side, since the DAC is 16-bit,
your one volt range would have a resolution
of 2^16 * 0.2 = 13,107 increments.

You mention an Op-Amp as a feature of your
'ideal' PIC; many PIC's have an on-board
Comparator, although you'd have to read up on
how it's used on your specific PIC. It
may or may not be what you want.

The Input is sampled for a 200 Hz frequency in a 1/2 sec timing window

Use a high-gain transistor to convert your
signal to a square wave and get your PIC to
count the number of 1->0 transitions in your
1/2 second window:

+5v
|
.-.
| | 10k
| |
'-'
|----- PIC digital input
Audio |
In || _R_ |/
-||--|___|--|
|| |>
|
---
-
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

 

On Sun, 31 Aug 2008 14:59:27 +0200, "petrus bitbyter"
<pieterkraltlaatditweg@enditookhccnet.nl> wrote:

"Paul E. Schoen" <pstech@smart.net> schreef in bericht
news:48b9f098$0$31984$ecde5a14@news.coretel.net...

"petrus bitbyter" <pieterkraltlaatditweg@enditookhccnet.nl> wrote in
message news:48b9b7c0$0$3112$e4fe514c@dreader26.news.xs4all.nl...

The D/A is not that easy.
The most simple solution will be PWM. You'll need a very good low pass
filter to get rid of the sample frequency which in turn will make output
changes slow.
A good and rock-stable way is an R/2R network. You'll need 14 resistors
and 7 output pins to achive 100 (128 to be excact) step resolution. Both
are described in:
http://ww1.microchip.com/downloads/en/AppNotes/00655a.pdf
A more attractive way is using a D/A-convertor. A TC1320 for instance is
a good choice. But the 8-pins chip uses an I2C interface which will be
hard to inplement for a beginner. You can however find example code at
Microchips. For the PIC a PIC12f629 will do.
In all solutions described above you will need an amplifier if you need
an output voltage >5.5V.

I agree with your recommendations, but I found that it is possible to make
a voltage doubler with the PWM output that can be programmed for a range
of
about 4 VDC to 6 VDC. It requires only two capacitors, two resistors, and
a diode. It might need to be monitored by one of the ADCs and trimmed, or
if the load is stable, you could make a table of PWM values and output
voltages. The LTspice ASCII for the circuit is at the end. The simulated
outputs with a 10 kHz PWM into a 5 kOhm load after 100 mSec are as
follows:


snip spice list

Think this comes very close to the OPs requirements. It'll be a challenge to
keep the voltage stable while measuring the frequency but even a 12F629 has
two timers available so it wil not be that hard. There's no need to drive a
PIC to its limits by using 5.5V power. Ordinary stabilized 5V will do. Where
did you got this idea from?

petrus bitbyter

I am really learning a lot from all of you and your experience. Being
a designer from scratch, my projects allows me great flexibility.

I can use a PIC Output voltage range of 4.1v to 5.1v now that I
understand that it is more acceptable by the PIC chip.

With processor control other ideas come to mind that would also
enhance what I am attempting do. The idea of controlling the sequence
of which circuit board turns on first and a final un-mute the sound
command is interesting.

Making that final decision of which processor to go with is
challenging but you have given me some part #'s to research.


Thank you all for you continued support.

* * * *

Christopher

Temecula CA.USA
http://www.oldtemecula.com