Wiring & diagram Info

This is a Simple Solar Cell Voltage Regulator Circuit Diagram. This device is designed to be a simple, inexpensive ‘comparator’, intended for use in a solar cell power supply setup where a quick ‘too low’ or ‘just right’ voltage indicator is needed. The circuit consists only of one 5V regulator, two transistors, two LEDs, five resistors, two capacitors, and one small battery. Although a 4-V battery is indicated, 4.5 V (3 alkalines in series) or 3.6 V (3 NiCd cells in series) will also work. 

The specifications of voltage regulator IC1 are mainly determined by the size and number of the solar cells and the current pull of the equipment connected to the output. Here the low-drop 4805 is suggested but other regulators may work equally well as long as you observe the output voltage of the solar cells. Transistors T1 and T2 are complementary types i.e. one each of the pnp and npn variety. 

Although the ubiquitous BC557B (pnp) and BC547B (npn) are indicated, any small-signal equivalents out of the junk box will probably do. The values of voltage dividers R1/R6 and R3/R4 may need to be adjusted according to the type of transistor and its gain, or according to the desired voltage thresholds. Using the resistor values shown in the schematic, LED D2 turns on fully when the voltage is just above 5 volts. 

LED D1 turns on when the voltage drops below 4.2 volts or so. Between those two thresholds, there is a sort of no man’s land where both LEDs are on dimly. A buzzer or other warning device could be connected across the terminals of LED D1 to give a more substantial warning if the voltage drops below operating limits. The current consumption of the circuit is about 20 mA at 5 V, and it decreases with the voltage supplied by the solar cells.

This is a simple PIC Security System Dials Your Cell Phone Circuit Diagram. Do-it-yourself phone dialer security system calls your cell phone, office etc. whenever a door or window is opened, or panic button is pressed. Great Home Alarm.

PIC Security System Dials Your Cell Phone Circuit Diagram



The schema consists of a small PIC microcontroller, assembly program, and a few other parts to detect a switch closure from an open door, window, or manual push button and then dial the cell phone number, and transmit a steady tone to indicate the source of the call. The schema uses the pulse dialing system to interrupt the line connection a number of times to indicate each digit. Pulse dialing (the oldest form of dialing) works by actually disconnecting or "hanging up" the phone line a number of times to indicate each digit. For example, the digit "5" would be dialed by disconnecting and reconnecting the line 5 times in short intervals of about 100mS. There is about a 1 second pause (with the line connected) between each digit. The timing is not critical and I was able to dial 411 and connect to the local information service just using a momentary push button switch in series with the phone line.

Circuit Operation:
In operation, the switch closure is detected on pin 7 of the processor which activates the reed relay and takes the line off-hook for 3 seconds to establish the dial tone. The processor then dials the number by opening and closing the relay a number of times for each digit. When dialing is complete, the processor waits 3 seconds and then transmits a steady tone of about 300Hz for 30 seconds through the modem transformer. The call is then terminated and the processor waits for the switch to open before resetting.

Design Considerations:

The PIC16F628 (18 pin) processor was selected because I had a few on hand and my homemade hardware programmer only accepts 18 pin devices. A smaller 8 pin device could have been used since only three I/O lines are needed, but the difference in cost is only about $1.50. One of the I/O lines (RA5) is used for programming and is always an input, but can used as a functional input so the switch closure could be detected on this line thus eliminating the need for one pullup resistor. But I elected to use 3 consecutive I/O pins (7,8,9) of the 8 bit port B and leave RA5 pulled up with a extra 10K resistor.

The output pins (8,9) that drive the relay and transformer are limited to 25mA of current each, so an extra transistor (2N2222A) was needed to supply additional current to the relay coil. The transformer resistance is around 100 ohms, so an additional 330 ohm resistor was added in series with pin 9 to limit the transformer current to around 10mA. An LED indicator and 330 ohm resistor were used on pin 8 to observe the dialing activity and indicate the line status. Several of the parts (relay, transformer and blocking capacitor) were obtained from an old 56K modem card.

The schematic shows a 47uF / 50 volt non-polarized capacitor used to block DC current to the transformer, however a regular polarized 50uF cap could be used if correct phone line polarity is observed. The modem was probably designed to work with unknown polarities at different locations, so a non-polarized cap was used. Its possible the cap and 470 ohm resistor can be replaced with a single resistor in series with the line to set the "off hook" line current to around 20mA. This may cause partial saturation of the transformer and reduced audio level, but might work well enough.

The power supply voltage is not critical and a 4.5 volt supply from three AA batteries should work. Or a switching type regulated 5 volt wall transformer can be used. The problem is insuring the relay gets enough voltage to operate. The rest of the schema should run on reduced voltage. I used a 4.2 volt cell phone charger that worked well.

The schema of the cell phone-controlled audio/video mute switch . This cell-phone-controlled audio/ video mute switch is highly useful in automobiles. The schema automatically disconnects power supply to the audio/video system whenever the mobile handset is lifted off the holder for making or receiving a call. You can use any readily available cell-phone holder with some mi-nor alterations or fabricate it yourself as shown in Fig. 1. 

Fig. 1: Proposed cell-phone holder

 

The schema is wired around IC LM555 (IC1), the CMOS version of timer NE555, as shown in Fig. 2. IC1 is used as a medium current line driver with either an inverting or non-inverting output. It can sink (or source) current of up to 50 mA only, so take care while handling it. The audio/video system is connected to the schema via normally opened (N/O) contacts of the relay.

 

Fig. 2: The schema of the cell phone-controlled audio/video mute switch

 

When the cell phone is in its holder, LDR1 does not receive any light from white LED1 and its resistance is high. As a result, the voltage at pin 2 of IC1 re-mains high to provide a low output at pin 3. The low output of IC1 activates relay RL1 and the audio/video system gets power supply via its N/O contacts. LED3 glows to indicate that the audio/video system is ‘on.’  When the handset is taken off the holder, light rays from LED1 fall on LDR1 and its resistance decreases. As a result, the voltage at pin 2 of IC1 de-creases to provide a high output at its pin 3. The high output of IC1 deactivates relay RL1 and the audio/video system does not get power supply. LED2 glows to indicate that the audio/video system is ‘off.’   Preset VR1 is used to control the sensitivity of the schema. Zener diode ZD1 is used for protecting white LED1 from the higher voltage. The schema works off a 12V car battery. Switch S1 can be used to manually switch on/off the audio/video system.