Electronics Projects, Circuit Diagrams

Electronic Circuits Design of Electronics Projects

Circuite electronice, scheme si montaje

Recent Posts

Pages: [1] 2 3 ... 10
RF / RF Circuits Frequency Counter with a PC interface
« Last post by Danmtang on May 22, 2017, 10:57:13 AM »
I build a lot of RF circuits, and often it’s convenient to measure and log frequency with a computer.
Previously I’ve built standalone frequency counters, frequency counters with a PC interface, and even hacked a classic frequency counter to add USB interface (twice, actually). My latest device uses only 2 microchips to provide a Raspberry Pi with RF frequency measurement capabilities.
The RF signal clocks a 32-bit counter  SN74LV8154 connected to a 16-bit IO expander MCP23017 accessable to the Raspberry Pi (via I²C) to provide real-time frequency measurements from a python script for $2.30 in components! Well, plus the cost of the Raspberry Pi. All files for this project are on my GitHub page.

The entire circuit is only two microchips! I have a few passives to clean up the RF signal (the RF input is loaded with a 1k resistor to ground, decoupled through a series 100 nF capacitor, and balanced at VCC/2 through a voltage divider of two 47k resistors), but if the measured signal is already a strong square wave they could be omitted. The circuit requires a gate pulse which typically will be 1 pulse per second (1PPS) and can be generated by dividing-down a 32.768kHz oscillator, a spare pin on a microcontroller, a fancy 1PPS time reference, or like in my case a GPS module (Neo-6M) with 1PPS output to provide an extremely accurate gate.

The connections are intuitive! The I2C address is 0x20 when A0, A1, and A2 are grounded. GPB(1-4) control the register select of the counter, and GPA(0-7) reads each bit of the selected register. The whole thing is controlled from Python, but could be trivially written in any language.

An advantage of this continuously running mode is that no clock cycles are lost, so a gate which accidentally fires a bit early due to jitter and cuts-off a cycle will compensate for it on a subsequent read. This is shown above, as a very stable 10MHz frequency reference is measured with this method. A “slow” 1PPS clock tick causes a reading slightly higher, compensated-for by the next reading being slightly lower. In this way, clock sources which are extremely accurate but suffer from low precision (like GPS time sources) are able to maximize the long-term measurement of frequency. Combining this frequency measurement technique with the ability to generate an analog voltage with a Raspberry Pi will allow me to perform some interesting experiments with a voltage controlled crystal oscillator.
Microcontrolere & DSP / Re: pupitru comanda analogic
« Last post by Gancoolza on May 15, 2017, 11:26:10 AM »
I've seen that it must be special and so interesting that I want to applaud.
Vanzari / Re: TV Daewoo ecran plat, diagonala 70 cm, aproape nou
« Last post by Benjaminr on April 27, 2017, 09:41:18 AM »
Can the content you need to explain to me can be added?
Microcontrolere & DSP / Re: mem 93c86
« Last post by Benjaminr on April 27, 2017, 09:04:34 AM »
How important are I to get from this content?
Microcontrollers and DSP / Can anyone help me with PIC16F723A Programming?
« Last post by yumi on March 29, 2017, 04:03:13 AM »
I am working with a PIC16F723A chip and I am trying to program it to toggle a pin (RA1) on and off. I am pretty sure I have the circuit setup correctly (below is what I have setup), but for some reason I get an error when trying to program it....

So, I am using MPLAB X IDE v1.70 on OS X version 10.8.2. The project configuration in MPLAB X is setup with the device of PIC16F723A, hardware tools of ICD 3, and compiler toolchain as XC8 (Location: /Applications/microchip/xc8/v1.12/bin). There is no supported plugin board. It is NOT setup to power the target circuit from the ICD 3.

The error I am getting is "Connection Failed.If the problem persists, please disconnect and reconnect the ICD 3 to the USB cable. If this does not fix the problem verify that the proper MPLAB X USB drivers have been installed."

The warning I am getting is "CAUTION: Check that the device selected in MPLAB IDE (PIC16F723A) is the same one that is physically attached to the debug tool. Selecting a 5V device when a 3.3V device is connected can result in damage to the device when the debugger checks the device ID. Do you wish to continue?"

Here is how I have the circuit setup...
PIC16F723A PIN 1 is connected to ICD3 MCLR PIC16F723A PIN 28 is connected to ICD3 ICSPDAT PIC16F723A PIN 27 is connected to ICD3 ICSPCLK PIC16F723A PIN 1/ICD3 MCLR is connected to external VDD (+3.3V) through a 10K resistor (I have also tried a 4.7K) PIC16F723A PIN 8 is connected to PIC16F723A PIN 19 PIC16F723A PIN 19 is connected to GND PIC16F723A PIN 20 is connected to VDD (+3.3V)

I am checking the chip using a Tektronix Oscilloscope and when I continue from the warning message, I see data being transfered on the ICSPDAT pin, but nothing has changed for the RA1 pin.

Here is the code I am using:
Code (Text):

#include <stdio.h>
#include <stdlib.h>
#include <pic16f723.h>

void main(void){
     int i = 0;
     TRISAbits.TRISA1 = 0; // RA1 to output
     ANSELAbits.ANSA1 = 0; // RA1 to Digital I/O

         PORTAbits.RA1 = 1;
         for(i = 0; i < 1000; i++);
         PORTAbits.RA1 = 0;
         for(i = 0; i < 1000; i++);
I have checked the circuit design several times, I have checked to make sure the chip is correct (the silkscreen on it says PIC16F723A-I/SP 1142D3V). I have also tried programming it by supplying +3.3V from an external supply and a +5.0V from an external supply.
Audio / Re: Recalculare boxa
« Last post by Hansahoney on March 15, 2017, 12:26:43 PM »

I was skeptical about this, and fortunately I had the chance to read something I did not understand yet.
Projects ideas / Re: Microcontroller Based Smoke Detector
« Last post by Hansahoney on March 15, 2017, 12:25:16 PM »

The knowledge that has been read from the content is great. It made me know a lot more. Can be really useful.
Decode mobile phones , car radio or other devices / Re: Car Radio Code ( decode )
« Last post by Liam on February 25, 2017, 03:19:14 PM »
Hi Guys

Could someone give me the code please.  Thanks.

Make: Renault
Model: AGC 1220 RF
Part Code: 281156951R
Supplier Code: 269779
Serial Number: 281156951RTC658
Decode mobile phones , car radio or other devices / Re: Car Radio Code ( decode )
« Last post by Pavel S on February 10, 2017, 02:32:05 PM »
Please help me, I need code for radio

Model: AGC-1220RF
Part code: 281156951R
Supplier code: 269779
Serial number: 281156951RTB632
Electronica Auto / Re: Coduri radiocasetofoane auto
« Last post by Horhel023 on January 23, 2017, 10:45:33 PM »
Buna ziua
ma poate ajuta si pe mine cineva cu codul pentru un casetofon de Opel Corsa C ?
Casetofonul este Blaupunkt 453116246 No:09115095 Type :CAR 2003 (F) UN 5
Mai are o serie 7649200321
Pe lateral mai scrie GM 020328247769

Multumesc !!
Pages: [1] 2 3 ... 10