Electronica Stuff.blogspot.com: January 2012

PIC diode tester

Galaxy 6:02 AM

PIC diode tester

This is a simple use of the PIC 16F84 about a diode tester.

Test procedure : We set «1» to PB0 and «0» to PB3. If diode is ok and opens, then at PA0 we have «1». If PA0 is «0», then the the diode has problem. With the program we manage what the PIC will do in each situation . If PA0 is «1», green led lights wich means that the diode is OK and if PA0 is «0» red led is lighting and the diode is problematic

Test continuous as follows: We give «0» at PB0 and «1» to PB3. If diode is OK and opens, then at PA0 is «1». If PA0 is «0», then diode has problem. If PA0 is «1», green led lights that means that diode is OK and if PA0 is «0» the red diode is lights that means the the diode is problematic.

Source Code

Credit of this diagram goes to Mr. Manolis Xenias

iButton electronic lock

Micro Controller

Galaxy 5:57 AM

iButton electronic lock

Since iButton DS1990A introduced in market from Dallas Semiconductor (MAXIM), it has been used in many applications concerning security, access control systems etc. In this project we will use iButton as a key to an electronic lock. This electronic lock can use many different kinds of iButtons and can store up to 9 different keys. One of the keys is the master key and is permanent stored in memory. With the use of master key we can add or remove slave keys.

This electronic lock can be used with any type of iButtons you may already have, since the only thing needed is the internal serial number, that's different for every iButton. The command used to read the serial number is the same for all iButtons. The iButton family code that goes with every iButton, can be anything and is calculated as part of the whole serial number. We must also notice that DS1990A series iButtons are the cheapest.

This electronic lock designed to work stand-alone and it's easy to construct. What the user sees (outside of the door for example) is a iButton socket and a led. From inside the door, we can open it using a simple push button. For the actual lock of the door a solenoid and a bold are used. Solenoid must be rated at 12Vdc. iButtons serial numbers stored in memory can be removed and updated when needed. One master key is used to manage the rest of them. Totally a number of 9 different keys can be stored in memory.

Schematic diagram is shown at figure 1. The circuit is build around an Atmel AT89C2051(U1) microcontroller. The port 1 (P1) of mcu is used to connect a 7-segment common anode led display. This led display will be used on the programming of additional keys. For the same reason a push-button labelled SB1 is connected on P.3.7. Storage of iButtons serial numbers is done on a 24C02 EEPROM (U3). It is connected on P3.4 (SDA) and P3.5 (SCL) of U1. The external iButton socked is connected on port P3.3 via XP2 pin array. The rest of components VD4, R3, VD5 and VD6 are used for protection of mcu ports. One pull-up resistor R4 is used as required from 1-wire protocol. An additional iButton socket is connected parallel with the predefined at pins XS1. This one is used for programming the keys. The door OPEN button is connected on P3.2 through XP1 connector, using the same protection components as above. The solenoid that does the lock is connected on XT1 connector. Solenoid is controlled from a power MOSFET IRF540 (VT3). Diode VD7 is added to protect MOSFET from voltage strikes due to solenoid inductance. Transistor VT3 is controlled from VT2, which reverses the logic state that's appears on P3.0, so on VT3 we have output 0V and 12V. This additional transistor is useful as it translates the mcu logic levels to 0V and 12V, capable to drive the solenoid.

Fig.1 Schematic diagram of iButton electronic lock

A led is used to indicate the state of the electronic lock, which is controlled from the same pin as the solenoid, using transistor TV1. This led is connected to the board using the same pin array XP2. But we need to ensure that the circuit will always work without supervision. For that reason we added ADM1232 (U2) that does the mcu reset pin control. This chip have a counter and voltage test circuits inside it. On pin P3.1 mcu produces pulses when it works right. If for a reason mcu freeze then U2 send it a reset pulse and work is resumed.

This electronic lock has it's own power supply on board, consisting of transformer T1, bridge rectifier VD9-VD12 and voltage regulator U4. As power backup an array of 10 AA batteries is used (BT1-BT10). Total capacity is 800mAH. When the circuit is connected on main voltage the battery pack is charged via R10 with a current of 20mA. This current is equal to 0.025C (where C is the batteries capacity) and that's a very small current depending on total capacity. That's put the battery on a steady charge to compensate losses among time and no charge completion detection is needed. That can be done as the excess energy is consumed in heat, that can not harm batteries as its low.

Overall board dimensions are 150х100х60mm. The most components are placed on the board, including the transformer. Batteries are placed on battery holders. In the place of AA batteries we could use a 12V sealed Lead - Acid battery. External components are connected on board with 2 or 3 pin connectors. Part numbers HG1, SB1 and XS1 are used only in programming mode so can be placed inside the plastic enclosure. Led VD3 can be placed on the face of enclosure, to indicate proper powering of board. A connection diagram is show on figure 2.

Fig.2 Connection diagram

When the door goes open, a 3 sec pulse is triggering the solenoid. When we press the door open button the door remains open as long as we push it.

The electronic lock can register 9 keys, plus one master key. Master's serial number is stored inside mcu. The rest of keys are stored on the external memory under slot 1 to 9. To add or remove a new key you should have the master key. Also master key can be used to open the door.

Fig. 3 Programming steps for adding a new key

To add a new key, the following steps should followed:

1. Press programming button.

2. Led displays letter «P» that indicated you entered programming mode.

3. Touch the master button in socket.

4. Led displays number «1». That's the current selected slot in memory.

5. Push the programming button to select a different programming slot for your new key.

6. Touch the new key to the socket.

7. The number on led display blinks, indicating ready to program.

8. Touch again the new key to confirm registration to memory.

9. If successfully registered the display stops blinking.

10. After 5 seconds, the program exits from programming mode.

The programming procedure to register a new key is displayed schematically on figure 3.

If you want to register more keys, then from step 9 you can go directly to step 5. These steps can be revised as many times as you like.

If after step 7, you find out that you selected wrong slot number and you don't want to loose that key, press programming button or just wait 5 seconds. When you press the button the slot number increases by one and memory hasn't changed yet. If you wait 5 seconds, programming mode will exit and nothing is going to register in memory. Generally in any programming step, you can wait 5 second to exit programming mode.

To remove an already registered key, you follow an almost same procedure, using only the master key. Basically, it's like registering the master key on the memory slot you would like to erase. This procedure is shown on figure 4.

Fig.4 Programming steps for removing a key.

During programming mode, the door will only open with the press of the OPEN button. Also, because the two iButton sockets are connected in parallel, you should avoid simultaneous touch of keys on both sockets.

Master's key serial number is stored on mcu's program memory, beginning from address 2FDH. The length of serial number is 8 bytes. The serial must be equal that is printed on top the iButton case, reading from left to right. On memory address 2FDH the control byte is registered, then on address 2FEH - 303H the next six bytes are registered, beginning with most significant byte. Finally the family code byte is stored on address 304H. For example a complete serial code should look like: 67 00 00 02 D6 85 26 01

The software block diagram shows on figure 5. The program starts, asking if a key has entered. If a key is entered, then it goes on reading the internal serial number. The next step is to check if this is the master key or another key already registered in memory. If the key is verified then the door is opened. Also the OPEN push button is checked, and if it's pressed the door opens.

Fig.5 Software block diagram

For the programming mode there exists two subprograms: PROGT and PROGS, whose block diagrams show in figure 6. The first is called when the serial number is read, in the programming phase and the second is called when the programming button is pressed. Programming of a new key is completed in three phases. When we press the programming button, we enter the programming mode. In this state the led displays «P» and the serial number of the key is checked to see if this is the master key, because this key is required to proceed on programming steps.

If this is the master key, we proceed on phase 2. Now, led is displaying the number of current selected memory slot, changing by pressing programming button. If we touch the key again, then it is registering on memory and we pass to phase 3. If we touch another key, this is also registered and we pass to phase 2. With the press of the button, we pass on phase 2 without registering any key.

If we don't touch anything in a period of 5 seconds, the program exits from programming mode. Block diagrams of figure 5 and 6 are simplified, but they give as an overall sense of program functionality.

It's upon your desire to extend the capabilities of this program, as it's open source, to fit your special needs.

Please Download Files below;

1.) Source code

2.) Binary File

3.) Project Document MS-word file

The credit of this diagram goes to Mr. Leonid Ridiko and Victor Lapitskiy

Play PIC

Micro Controller

Galaxy 5:32 AM

Play PIC

This is a new design of a tutorial board based on the popular PIC16F84A microcontroller. It features eight single leds, a 7-segment display, an LCD display and five push buttons. It is an ideal solution for the beginner to take his/her first programming steps in the world of microcontrollers. Having an in-circuit-programming (ICP) header, it can be easily reprogrammed without unplugging the microcontroller each time, provided that the programmer also supports this feature (like OziPic’er).

Connections

PIC16F84A......................Feature
RA0................................JP2 - S3 – JP4
RA1................................JP2 - S4 – JP4
RA2................................JP2 - S5 - JP4
RA3................................JP2 - S6 - JP4
RA4................................JP2 - JP4

PIC16F84A.......................Feature
RB0.........................JP2 – LED1 – 7 Seg (dp) – S7 Debounce - Buzzer
RB1.........................JP2 – LED2– 7 Seg (a) – LCD RS
RB2.........................JP2 – LED3– 7 Seg (b) – LCD R/W
RB3.........................JP2 – LED4– 7 Seg (c) – LCD E
RB4.........................JP2 – LED5– 7 Seg (d) – LCD DB4
RB5.........................JP2 – LED6– 7 Seg (e) – LCD DB5
RB6.........................JP2 – LED7– 7 Seg (f) – LCD DB6
RB7.........................JP2 – LED8– 7 Seg (g) – LCD DB7

Feature Description

- S1 switches the board on and off. When on, the indicator led LED9 is lit.

- S2 resets the microcontroller.

- S8 switches the LCD display on and off

- S9 switches the eight individual leds AND the 7-segment display on and off.

- Push buttons S3 to S6 correspond to RA0-RA3 inputs. They are enabled or disabled by the SW2 dip switch.

- The SW1 dip switch enables or disables the following features :

1. Connects RB0 (used as output) to LED1.

2. Connects RB0 (used as interrupt input) to S7.

3. Enables the debouncing circuit for interrupt switch S7.

4. Connects RB0 (used as output) to the buzzer.

This dip switch must be either 1000 or 0100 or 0110 or 0001.

- The 7-segment display is always connected to the individual leds. Its seven segments correspond to LED2 to LED8 (RB1 to RB7) and the decimal dot to LED1 (RB0). This correspondence enables the 7-segment display to work together with the interrupt switch S7, which is connected to RB0.

- JP4 is an 6-screw external input connector for RA0-RA4. When used, the corresponding input switches S3-S6 must be turned off by SW2. Last screw is ground.

- JP2 is a 14 pin test terminal. A voltmeter or logic analyzer can be connected any time to monitor the signal traffic in the circuit. Last pin is ground.

- JP1 is the ICP header. When in-circuit-programming is performed, the board must be OFF (by S1), as well as the LCD (by S8) and leds (by S9).

- JP3 is a 14-pin connector for the LCD module. Contrast can be adjusted by trimmer R21.

- The board can be powered either by a 9V battery or a 6-12 V power supply.

PDF versions of the schematic and PCB are included. The board has been sucessfully build and it is depicted on the following

Photos

The top photo shows the in-circuit-programming procedure with the help of an appropriate programmer (like OziPic'er) which features an ICP header. In order for the procedure to work correctly, the LCD module has to be disconnected from its socket during programming.

Credit of this diagram goes to Mr. Vassilis Papanikolaou

Mobile Phone Calling Detector

Tracking Devices

Galaxy 7:36 AM

Mobile Phone Calling Detector

Flashes a LED when detecting an incoming call
Powered by one 1.5V cell

Parts:
R1 100K 1/4W Resistor
R2 3K9 1/4W Resistor
R3 1M 1/4W Resistor
C1,C2 100nF 63V Polyester Capacitors
C3 220µF 25V Electrolytic Capacitor
D1 LED Red 10mm. Ultra-bright (see Notes)
D2 1N5819 40V 1A Schottky-barrier Diode (see Notes)
Q1 BC547 45V 100mA NPN Transistor
IC1 7555 or TS555CN CMos Timer IC
L1 Sensor coil (see Notes)
B1 1.5V Battery (AA or AAA cell etc.)

Device purpose:
This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED.
The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call.

Circuit operation:
The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The IC's output voltage is doubled by C2 & D2 in order to drive the high-efficiency ultra-bright LED at a suitable peak-voltage.

Notes:
Stand-by current drawing is less than 200µA, therefore a power on/off switch is unnecessary.
Sensitivity of this circuit depends on the sensor coil type.
L1 can be made by winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Remove the coil from the former and wind it with insulating tape, thus obtaining a stand-alone coil.
A commercial 10mH miniature inductor, usually sold in the form of a tiny rectangular plastic box, can be used satisfactorily but with lower sensitivity.
IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.
Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type is a very good choice.