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flashlight 2 batt

Next we have the circuit from an actual LED flashlight. This circuit is so small that it fits inside the “bulb base” behind the reflector in a 2C cell flashlight. All of the parts are surface mount except the LEDs, the 2N3904 and the coil. The LED in the schematic is actually 8 5mm ultra bright white LEDs. Unfortunately, once again we have an unmarked surface mount capacitor.

Instead of a CdS cell, a flashlight of course has a switch. In our walkway marker circuit, one of the transistors took the place of the switch, so the oscillator section was really 2 coils and a transistor. Now instead, this oscillator has one coil and two transistors. The coil is also different. It is a larger wire wound I core instead of the type that resembles a resistor. A larger coil and transistor means more power since it has to drive 8 LEDs instead of just one. Plus the white LEDs have a 4v voltage drop instead the 3v drop of the amber one from the walkway marker. more...

These are the little lights with the stake on the bottom that you can push into the ground along your driveway or sidewalk and have the solar panel on top. The solar cell charges a AA NiCd battery during the day and at night the battery powers the LED. The circuit board in this particular model was originally designed to hold a pair of 5mm amber LEDs, but the manufacturer apparently found a source of higher power 10mm amber LEDs and the final product only needs one of these. Due to the limited space, many of the components are surface mount. The transistors are both 2N3904 equivalent surface mounts. Unfortunately, the capacitor is also surface mount and is unmarked.

The charging circuit is fairly simple and has a photovoltaic solar cell to charge the battery and a diode to prevent the battery from powering the cell when it’s dark. Now moving along, there is a cadmium sulphide (CdS) photo resistor, a 10k resistor and a 1k resistor that forms a voltage divider at the base of Q1. When light hits the photo resistor, it has a low resistance which is amplified by the transistor. The collector is tied to the base of the left hand transistor, so when it’s on it clamps its base to ground and prevents it from oscillating. When it’s dark and the CdS Cell has a high resistance, the right transistor is off which allows the rest of the circuit to begin oscillating more...

I’ve been fascinated by the LM335 for some time -maybe my obsession with stability finally gave way to my fascination with a circuit with intentional thermal drift. I finally bought some the other day, and to check one out, I hooked it up as a thermometer, based the National Semiconductor application note.

The circuit consists of two parts: The LM335 and its adjustment. The output of the LM335 is 10 millivolts per degree C, with 25 degrees C corresponding to 2.982 VDC. A reference circuit provides a zero reference voltage. It is adjusted to (2.982 volts - (25 degrees x 10 millivolts/degree) = 2.832 volts. To read the temperature of the LM335 directly in degrees C, connect the + lead from a high impedance DVM to the output pin and the - end of the DVM to the 2.732 volt pin.

The factor of 10 millivolts per degree C is equivalent to 10 millivolts per degree K, since a change of one degree C is equal to a change of one degree K. The difference in the two scales is only their offsets. The melting point of water ice is 0 degrees C and 273.15 degrees K. The boiling point of water is 100 degress C and 373.15 degrees K more...

The basic digital circuits are Flip Flop and Counter, both are here. This circuit can be cascaded to make even a 6 digit event counter, even a simple frequency counter can be made.
These are best done with microcontrollers today. Then what if you have to design your own microcontroller on a FPGA, so the basics have to be sound, hence you have to know what gates, flip flops and counters are.
see the seven segment display. Inc, Dec, and Set buttons are momentary acting and Clk Button is latching type. The Dip Switch in the also can be set.
a.Set the DIP Switch as you like and then Press the Set button. The BCD value will be at the 4029 output, The Decimal value will be seen in the seven segment Display. Now try for different dip switch settings and see the BCD and Decimal output.
b.Now Press The Inc and Dec pushbuttons. Set it to Increment up-count or Decrement which is down-count. This is a simple flip flop control.
c.Now Click the Clk - clock or count button, the switch will latch, press it again to release. If you toggle it once the counter will get a single pulse and it will count it, see the BCD and decimal displays. Now you turn it on and leave it, the counter will keep counting one per second till you turn it off, the clock nand gate is wired to be an oscillator.
the decimal point LED of display is given to Carry Out pin of 4029 so observe this at 9 and 0 or transitions.
Add 104 CD, 0.1uF ceramic disc cap to all the ICs across the supply pins. Also add a 104 CD cap across Inc switch and one across the Set switch for power on default settings more...

This is circuit Simple Light Meter, I use Poto Resisitor for sensitivity light.
And display ligh value by M1 or mini meter 1mA.
It is very small circuit,have lot part electronics and,very low cost.
R-100K for Control light sensitivity
Cds = Poto Resistor more...

Max. range: 9,950 meters with two digits
Slip it in pants’ pocket for walking and jogging


R1,R3____22K 1/4W Resistor
R2________2M2 1/4W Resistor
R4________1M 1/4W Resistor
R5,R7,R8__4K7 1/4W Resistor
R6_______47R 1/4W Resistor
R9________1K 1/4W Resistor

C1_______47nF 63V Polyester Capacitor
C2______100nF 63V Polyester Capacitor
C3_______10nF 63V Polyester Capacitor
C4_______10µF 25V Electrolytic Capacitor

D1_______Common-cathode 7-segment LED mini-display (Hundreds meters)
D2_______Common-cathode 7-segment LED mini-display (Kilometers)

IC1______4093 Quad 2 input Schmitt NAND Gate IC
IC2______4024 7 stage ripple counter IC
IC3,IC4__4026 Decade counter with decoded 7-segment display outputs IC

Q1,Q2___BC327 45V 800mA PNP Transistors

P1_______SPST Pushbutton (Reset)
P2_______SPST Pushbutton (Display)

SW1______SPST Mercury Switch, called also Tilt Switch
SW2______SPST Slider Switch (Sound on-off)
SW3______SPST Slider Switch (Power on-off)

BZ_______Piezo sounder

B1_______3V Battery (2 AA 1.5V Cells in series)

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants’ pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking. A beeper (excludable), signals each count unit, occurring every two steps.
A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on. For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together.
Obviously, this is not a precision meter, but its approximation degree was found good for this kind of device. In any case, the most critical thing to do is the correct placement of the mercury switch inside of the box and the setting of its sloping degree more...

= Warn the heat in an automobile
This circuit sets up in its automobile will perform to warn give testimony know before your car is will born the heat too much. By use main part electronic be IC 741 and Thermistors. By have LED Flasher with usual rate , when the temperature arrives at location value keeps with before VR1. When the temperature increases continuously LED as a result stick bright forever. By control checking temperature has with VR2. This circuit gives with power supply of an automobile has normally for the frequency of winking can fix with C1. A friend can see the detail adds in the circuit. more...

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