Diagram SOlution

Monday, October 20, 2014

Dimmable White LED Lamp

Nowadays you can buy white LEDs, which emit quite a bit of light. They are so bright that you shouldn’t look directly at them. They are still expensive, but that is bound to change. You can make a very good solid-state pocket torch using a few of these white LEDs.

The 12V DC input voltage is routed through the 1A fuse and the on/off switch. The 1N4001 diode acts as a crowbar device. If reverse polarity is applied, the fuse will blow and the rest of the circuitry will be protected. Power is sent to the LM2941CT voltage regulator IC. The regulator is wired to produce a voltage range from 5.5V (dim) to 8.3V (bright).

The 4.7K resistor across the 1K brightness adjustment potentiometer produces a non-linear brightness adjustment to compensate for the eyes logarithmic brightness perception response. The LEDs are organized in six series groups of three with a 24 ohm current limiting resistor on each group. This arrangement limits the maximum current through each LED group to around 20mA.

Connect the DC input terminals to a 12V source, such as a 12V lead acid battery. Be sure to observe the correct polarity. Turn the power switch on and adjust the brightness adjustment for the desired brightness.

Parts

1X LM2941CT low-dropout voltage regulator
1X aluminum heat sink
1X 1A DC rated fuse
1X DC switch
1X 1N4001 diode
2X 1K 1/4W resistors
2X 4.7K 1/4W resistors
6X 24 ohm 1/4W resistors
1X 1K linear potentiometer
18X 5mm white LEDs, 20mA max
1X 22uF 16V electrolytic capacitor
1X 100nF 25V monoblock capacitor

Thursday, October 16, 2014

Maximum Minimum Voltage Indicator

This circuit indicates which of three voltages in the range from about about -4V to about +4V - at A, B and C - is the highest by lighting one of three indicator LEDs. Alternatively, it can be wired to indicate the lowest of three voltages or to indicate both the highest and lowest voltages. Op amps IC1a, IC1b & IC1c are wired as comparators, while the three indicator LEDs and their series 1kO current limiting resistors are strung across the op amp outputs to implement the appropriate logic functions.

Circuit diagram:

Maximum Minimum Voltage Indicator Circuit Diagram

For example, LED A will light only when pin 8 of IC1c is low (ie, A greater B) and pin 7 of IC1b is high (ie, A greater C). Similarly, LED B will light only when pin 8 of IC1c is high (ie, B greater A) and pin 1 of IC1a is low (ie, B greater C). LED C works in similar fashion if the voltage at C is the highest. Note that if all the LEDs and their parallel 1N4148 diodes are reversed, the circuit will indicate the lowest of the three input voltages. And if each 1N4148 diode is replaced by a LED, the circuit will indicate both the highest and lowest inputs.

Author: Andrew Partridge - Copyright: Silicon Chip

Automatic Plant Irrigator

The circuit presented here waters your plants regularly when you are out for a vacation. The circuit comprises a sensor part built using only one op-amp (N1) of quad op-amp IC LM324. Op-amp N1 is configured here as a comparator. Two stiff cop-per wires are inserted in the soil containing plants. As long as the soil is wet, conductivity is maintained and the circuit remains off. When the soil dries out, the resistance between the copper wires (sensor probes A and B) increases. If the resistance increases beyond a preset limit, output pin 1 of op-amp N1 goes ‘low’.

Circuit diagram :

Automatic Plant Irrigator Circuit Diagram

This triggers timer IC2 (NE 555) configured as a monostable multivibrator. As a result, relay RL1 is activated for a preset time. The water pump starts immediately to supply water to the plants. As soon as the soil becomes sufficiently wet, the resistance between sensor probes decreases rapidly. This causes pin 1 of op-amp N1 to go ‘high’. LED1 glows to indicate the presence of adequate water in the soil. The threshold point at which the output of op-amp N1 goes ‘low’ can be changed with the help of preset VR1. To arrange the circuit, insert copper wires in the soil to a depth of about 2 cm,keeping them 3 cm apart. When the soil the water. LED1 glows up as the water reaches the probes.

For small areas a small pump such as the one used in air coolers is able to pump enough water within 5 to 6 seconds. The timing components for IC2 are selected accordingly. The timing can be varied with the help of preset VR2. The circuit is more effective indoors if one intends to use it for long periods. This is because the water from reservoir (bucket, etc) evaporates rapidly if it is kept in the open. For regulating the flow of water, either a tap can be used or one end of a rubber pipe can be blocked using Mseal compound, with holes punc-gets dried, adjust VR1 towards ground rail until LED1 turns off and relay RL1 is energised. The motor starts pumping tured along its length to water several plants.

Author: Priyank MudgaL - Copyright: Efymag

Simple UPS Power Supply

This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply.

This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit.

TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is maintained by the battery. The circuit below simulates a working circuit with mains power applied:

Between terminals VP1 and VP3 the nominal unregulated supply is available and a 5 Volt regulated supply between VP1 and VP2. Resistor R1 and D1 are the charging path for battery B1. D1 and D3 prevent LED1 being illuminated under power fail conditions. The battery is designed to be trickle charged, charging current defined as :-

(VP5 - 0.6 ) / R1
where VP5 is the unregulated DC power supply voltage.

D2 must be included in the circuit, without D2 the battery would charge from the full supply voltage without current limit, which would cause damage and overheating of some rechargeable batteries. An electrical power outage is simulated below:

Note that in all cases the 5 Volt regulated supply is maintained constantly, whilst the unregulated supply will vary a few volts.

Standby Capacity
The ability to maintain the regulated supply with no electrical supply depends on the load taken from the UPS and also the Ampere hour capacity of the battery. If you were using a 7A/h 12 Volt battery and load from the 5 Volt regulator was 0.5 Amp (and no load from the unregulated supply) then the regulated supply would be maintained for around 14 hours. Greater A/h capacity batteries would provide a longer standby time, and vice versa.

Voice Scrambler

With this circuit you can modify how your voice sounds by changing the pitch of your voice. This circuit can be connected to a phone and with a duplicate circuit on the end of the phone line, you can have a scrambled voice communication. The way the circuit works is as follows: If we cut the circuit in half at the T2 transformer and include the LM324 on the left side, you will see that the LM324 portion of the circuit is a tone oscillator which shifts the frequency of all input signals to a new higher frequency. When the voice and the tone oscillator mix frequencies the voice is not recognized. The voice signal is then inputted to the second stage which again shifts the voice signal again. I recommend that the first stage be tuned to a frequency that is 100hz lower then the second stage.

Simple Sleeping Aid Schematic Circuit Diagram

Many people experienced sleeping well in natural surroundings, into a tent or a wooden hut. This fact is due not only to the healthy atmosphere but also from our unconscious ability to perceive natural Earths magnetic-fields. The circuit generates this type of Geo-magnetic-fields and lets us perceive them: in this manner our brain is surrounded by an ideal environment for a sound sleep. (N.B. Basic ideas for this circuit are coming from German papers).

Circuit operation:

IC2C and IC2D generate two square waves at about 1.2 and 5 Hz respectively. These wave-forms are converted into 60µS pulses at the same frequencies by means of C5 & C6 and mixed at Q1 Base. This transistor drives the Radiator coil with a scalar series of pulses of 60µS length and 9V amplitude. IC1, IC2A & IC2B form the timer section.

C1 & R2 provide auto-reset of IC1 at switch-on. The internal oscillator of IC1 drives the 14 stage ripple counter and, after about 15 minutes, output pin 1 goes high. Pin 3 of IC2A goes low and stops IC2C & IC2D oscillation. If SW2 is left open (Alternate mode operation), after 15 minutes pin 1 of IC1 goes low, pin 3 of IC2A goes high and oscillators are enabled again.

If SW2 is closed (Stop mode operation), the first time output pin 1 of IC1 goes high, the internal oscillator of the IC is disabled by means of D1. Therefore the circuit remains off until a reset pulse is applied to pin 12 by means of P1 or when the whole device is switched-off and then restarted. The same thing occurs when SW1 is switched on 30 or 60 minutes positions, obviously changing time length.

IC2B drives pilot LED D2 which operates in the following three modes:

flashes quickly and almost randomly when the Radiator coil is driven
flashes somewhat slowly and regularly when the Radiator coil is pausing during the Alternate mode operation
is off when the circuit auto-stops (Stop mode operation)

Circuit diagram:

Sleeping Aid Circuit Diagram

Parts:

R1 = 1K 1/4W Resistors
R2 = 10K 1/4W Resistor
R3 = 10M 1/4W Resistors
R4 = 2M2 1/4W Resistors
R5 = 1K 1/4W Resistors
R6 = 10M 1/4W Resistors
R7 = 2M2 1/4W Resistors
R8 = 4K7 1/4W Resistors
R9 = 4K7 1/4W Resistors

C1 = 47µF 25V Electrolytic Capacitors
C2 = 100nF 63V Polyester Capacitor
C3 = 330nF 63V Polyester Capacitors
C4 = 330nF 63V Polyester Capacitors
C5 = 15nF 63V Polyester Capacitors
C6 = 15nF 63V Polyester Capacitors
C7 = 47µF 25V Electrolytic Capacitors

D1 = 1N4148 75V 150mA Diodes
D2 = LED (any type) (see Notes)
D3 = 1N4148 75V 150mA Diodes
D4 = 1N4148 75V 150mA Diodes
D5 = 1N4148 75V 150mA Diodes

IC1 = 4060 14 stage ripple counter and oscillator IC
IC2 = 4093 Quad 2 input Schmitt NAND Gate IC
Q1 = BC327 45V 800mA PNP Transistor
L1 = Radiator coil (see Notes)
P1 = SPST Pushbutton
SW1 = 2 poles 4 ways rotary switch
SW2 = SPST Slider Switch
B1 = 9V PP3 Battery, Clip for PP3 Battery

Features:

Generates a natural electromagnetic-field
Makes easier to fall asleep
Induces a prolonged and sound sleep without drugs
No side effects

Use of this circuit:

Select a timing option by means of the rotary switch SW1.
Choose 15, 30 or 60 minutes operation.
Select "Stop" or "Alternate" mode operation by means of SW2.
With SW2 closed (Stop mode operation) the electromagnetic radiation stops after the pre-set time is elapsed.
With SW2 opened (Alternate mode operation) the device operates for the pre-set time, then pauses for the same amount of time: this cycle repeats indefinitely.
Place the unit under the pillow and sleep like a log.
To reset a cycle press P1 pushbutton.

Notes:

L1 is obtained by winding randomly 600 turns of 0.2 mm. enameled wire on a 6 mm. diameter, 40 mm. long, steel bolt. Secure the winding with insulating tape.
Mean current drawing is about 7mA, decreasing to less than 4mA during pauses when in Alternate mode operation.
Battery life can be dramatically increased omitting LED D2 and its associated resistor R5.
Use a plastic box to enclose the circuit: metal cases can severely limit electromagnetic radiation.

Friday, September 26, 2014

Numeric Water Level Indicator

Most water-level indicators for water tanks are based upon the number of LEDs that glow to indicate the corresponding level of water in the container. Here we present a digital version of the water-level indicator. It uses a 7-segment display to show the water level in numeric form from0 to 9. The circuit works off 5V regulated power supply. It is built around priority encoder IC 74HC147 (IC1), BCD-to-7-segment decoder IC CD4511 (IC2), 7-segment display LTS543 (DIS1) and a few discrete components. Due to high input impedance, IC1 senses water in the container from its nine input terminals. The inputs are connected to +5V via 560-kilo-ohm resistors.

The ground terminal of the sensor must be kept at the bottom of the container (tank). IC 74HC147 has nine active-low inputs and converts the active input into active-low BCD output. The input L-9 has the highest priority. The outputs of IC1 (A, B, C and D) are fed to IC2 via transistors T1 through T4. This logic inverter is used to convert the active-low output of IC1 into active-high for IC2. The BCD code received by IC2 is shown on 7-segment display LTS543. Resistors R18 through R24 limit the current through the display.

image Numeric Water-Level Indicator circuit diagram

When the tank is empty, all the inputs of IC1 remain high. As a result, its output also remains high, making all the inputs of IC2 low. Display LTS543 at this stage shows 0, which means the tank is empty. Similarly, when the water level reaches L-1 position, the display shows 1, and when the water level reaches L-8 position, the display shows 8. Finally, when the tank is full, all the inputs of IC1 become low and its output goes low to make all the inputs of IC2 high. Display LTS543 now shows 9, which means the tank is full. Assemble the circuit on a general-purpose PCB and enclose in a box. Mount 7-segment LTS543 on the front panel of the box. For sensors L-1 though L-9 and ground, use corrosion-free conductive-metal (stainless-steel) strips.
Copyright: EFY Mag