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Author Topic: A simple question about PWM and PIC12F683  (Read 6394 times)
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sughoi
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« on: July 12, 2008, 01:34:38 13:34 »

I want to ask a simple question. Actually I want to make a simple circuit that uses the same principles of a USB pic programmer. This circuit will be supplied with 3.7 V DC and via a PWM signal (from PIC12F683, of course will be supplied with 3.7 V DC) I want to get 7 V DC. I found K128 USB PIC programmer’s circuit diagram. But I’m confused.

I’m sending the diagram. Could somebody please help me?  Huh

http://rapidshare.com/files/129111037/PIC_Programmer_All-Flash_USB_Kit128_Manual.pdf

Thank you….
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sughoi
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« Reply #1 on: July 12, 2008, 10:01:32 22:01 »

Gentlemen I began to work on another circuit diagram. You know Brenner 8  USB PIC programmer. There is a BAT43 diode in order to get 10V DC. Thanks god I got this programmer, so I took my multimeter and measured input voltage as 4.8 V and I surprised that output of BAT43 is 10V DC. But when I try to get the same thing on my breadboard I can’t. I am confused……

You can find the circuit  diagram below..

http://rapidshare.com/files/129204144/brenner8p5.pdf.html

Please somebody help me…


Posted on: July 12, 2008, 09:17:28 21:17 - Automerged

I learned something about this programmer via its datasheet but it was written in german so somebody please translate these information.. I know now BAT43 works as a boost converter..
here you can find some information about boost converter..

http://www.coilgun.eclipse.co.uk/electromagnetic_pistol_voltage_converter_design.html
----------------------------------------------
6.1.4  Programmierspannungserzeugung
Die PICs benötigen zur Programmierung eine Programmierspannung von 10 .. 1
(je nach Typ). Sie wird aus der Betriebsspannung durch einen Boost-Konverter
erzeugt. Der PIC18F2550 gibt am Pin 13 ein 100kHz-Rechtecksignal aus, desse
Pulsweitenverhältnis einstellbar ist. 
Die an mit dem Boost-Converter erzeugte Spannung beträgt theoretisch
 
Vpp = 4,7V * Periode / off-zeit
 
wobei "Periode" die Dauer eine Rechteckschwingung ist, wärend "off-zeit" der lo
Teil dieser Periode ist. Durch Änderung von "off-zeit" kann die Vpp-Spannung
eingestellt werden.
In der Praxis gibt einige Seiteneffekte, die durch eine Kalibrierung kompensiert
werden müssen.
 
Zwei widerstände bilden einen Spannungsteiler über den der PIC18F2550 die
erzeugte Vpp-Spannung messen kann (Pin 3).

----------------------------------------------------------

and here is the original datasheet

http://rapidshare.com/files/129212583/b8_handbuch.pdf.html
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pelctronics
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« Reply #2 on: July 12, 2008, 10:33:43 22:33 »

Bat 45 is fast switching diode and nothing else ,he is just rectifier .. main thing do inductor (coil ) because electromagnetic energy stored in him   and charge  the capacitor in frequency  of switching...so you need coil, rectifier diode , capacitor,switch (transistor, fet,and so on) and you must send pwm impuls to switch.
that you may do from pic or by some other oscillator.  If frequency of switching is more you need less coil on inductor and less capacitor..this is basic thing how to get more voltage from less... Wink
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sughoi
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« Reply #3 on: July 12, 2008, 11:18:34 23:18 »

ok then, how can I calculate the values with these components. For example I want to get 8 volt dc from 3.7 V dc,  now what must be the values af these components (osilator freq, R , C, L ). How can estimate these vaules...Thank you.
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pelctronics
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« Reply #4 on: July 12, 2008, 11:56:02 23:56 »

He he,. it's too complex and expensive to produce supply by own. because you may burn your artistic work Smiley
better is to buy chip which have  already all parts in him Wink just put few passive elements around.
Mc34063a is SMPS controller check on goggle  for data sheet and circuit diagrams... Smiley   
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hemlig
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« Reply #5 on: July 13, 2008, 02:14:45 02:14 »

use google and search for: step up converter
there will be many hits that might be suitable for what you're trying to do.
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Walkura
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« Reply #6 on: July 13, 2008, 07:19:36 07:19 »

Maybe this datasheet will shed some light on it .
http://ww1.microchip.com/downloads/en/AppNotes/01047a.pdf
What you mean is a buckboost regulator .
You can do that very simple with for instance a sg3525 or with pic processor .
If its your first time i would say use a optical isolated gatedrive.
When you destroy your mosfet at least your logic survives  Grin

Good luck and calculate carefull
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« Reply #7 on: July 13, 2008, 09:42:43 21:42 »

A nice 5V to 9v inverver is on nearly every network card.
some in 16pin and others in 28pin. Data is found on the internet.
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sughoi
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« Reply #8 on: July 13, 2008, 09:50:31 21:50 »

thanks for every response
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sughoi
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« Reply #9 on: July 20, 2008, 04:16:48 16:16 »

I tried almost everything but I could not be succeed. I have one more question. Everyone knows brenner8 usb pic programmer. I have one. I made a booster converter as on it. when I use pwm signal on this programmer (from 18F2550) my boost converter works.(I have to add that I measured approximately  500mv from CCP1 pin and I read this signal is 100KHz). But when I try to generate the same signal with my 12F683 my boost converter does not work!

I am going to be crazy. Does anyone have the configuration of that Brenner8 programmer?
-CCPR1L, CCPR1H, CCP1CON, T2CON, PR2 etc. I want to ask that question to SPRUT but I could not find him e-mail adress.

Please someone help me...

Posted on: July 20, 2008, 03:53:54 15:53 - Automerged

This is the firmware link for Brenner8 programmer..

http://rapidshare.com/files/131118669/b8_fw_0_11.hex.html

May be this can be helpful .
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Walkura
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« Reply #10 on: July 20, 2008, 05:25:48 17:25 »

What duty cycle did you set in your program ?
From what i read i assume that with the pic2550 you have 10% (Vmeasured = Volts * duty cycle)
I don't know the programmer you mentioned but i can advise you a good read .
http://www.sonsivri.com/forum/index.php?topic=12417.0
Especialy pressman and brown tell in quite simple terms how to calculate a buck boost .
With that information you will know exactly what coil ,duty cycle etc etc. for any given wished voltage .

Good luck .
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« Reply #11 on: July 20, 2008, 05:32:16 17:32 »

Hi, I have one example. I use PIC12F629.
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Walkura
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« Reply #12 on: July 20, 2008, 05:37:48 17:37 »

Sorry for my double reply i didnt see the German text before  Embarrassed
----------------------------------------------
6.1.4  Programmierspannungserzeugung
(creation of the programming voltage)
Die PICs benötigen zur Programmierung eine Programmierspannung von 10 .. 1
(je nach Typ).
The pic's require for programming a programming voltage from 10...1 (according to type)
 Sie wird aus der Betriebsspannung durch einen Boost-Konverter
erzeugt.
This is made out of the powersupply by a (buck) boost converter .
 Der PIC18F2550 gibt am Pin 13 ein 100kHz-Rechtecksignal aus, desse
Pulsweitenverhältnis einstellbar ist.
The pic18f2550 gives at pin 13 a 100 Khz squarewave of which you can adjust the dutycycle .
Die an mit dem Boost-Converter erzeugte Spannung beträgt theoretisch
The voltage created with the boost converter is in theory
Vpp = 4,7V * Periode / off-zeit
 Vpp = 4,7 Volt * period / time off
wobei "Periode" die Dauer eine Rechteckschwingung ist, wärend "off-zeit" der lo
Teil dieser Periode ist.
Where as *period* is the time of the squarewave and *off-time* the low part of this period .
 Durch Änderung von "off-zeit" kann die Vpp-Spannung
eingestellt werden.
By changing the *off-time* you can set the programming voltage .
In der Praxis gibt einige Seiteneffekte, die durch eine Kalibrierung kompensiert
werden müssen.
In practicle use it gives some side effects that will have to be compensated by calibration .
 
Zwei widerstände bilden einen Spannungsteiler über den der PIC18F2550 die
erzeugte Vpp-Spannung messen kann (Pin 3).
2 resistors are used to create voltage devider that can measure the over the pic18f2550 created Vpp (Pin3)

----------------------------------------------------------
I hope its a little clear ,although i understand it ,German aint my native language  Wink
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sughoi
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« Reply #13 on: July 20, 2008, 07:02:54 19:02 »

I am going to try these and give you the pesponse....

Posted on: July 20, 2008, 06:27:59 18:27 - Automerged

Gentlemen I found my mistake. I made the procedure manually (by     ON, Delay, OFF, Delay) it works. But when I try to get PWM signal from PWM generator I get nothing due to wrong register calculation. Then I found that 4KHZ freq and %10 duty cycle is excellent for my application. So if I want to get that signal from 18F252 what must be the registers value. (PR2, T2CON, CCP1CON......). Thank you so much
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sughoi
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« Reply #14 on: July 20, 2008, 09:13:38 21:13 »

I used MikroC ready libraries I solved the problem..(for now)
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