Wireless Baby Monitor Circuit Project

A baby monitor can help you find peace of mind. You can now monitor your sleeping baby with this wireless baby monitor. It is a radio system used to remotely listen to sounds made by an infant. Simply place the circuit near your sleeping baby and listen through an FM receiver from any other room in the house. It can also alert you if the baby wakes up in the middle of the night.

 Wireless Baby Monitor Circuit Diagram

The circuit is built around a low-power audio amplifier using LM386 (IC1), hex inverting Schmitt trigger 74HC14 (IC2), voltage regulator 7805 (IC3), 10MHz crystal (XTAL1), varactor diode 1SV149 (D1) and a few other components. A parallel resonant oscillator circuit is formed around inverter gate N1 along with crystal (XTAL1), resistor R3, capacitors C3 and C4 and varactor diode D1. It generates square waves at the fundamental frequency of 10MHz of crystal.

Fig. 2: PCB of the baby monitor circuit

The signal is buffered by gate N2 and further boosted by parallel inverter gates N3, N4, N5 and N6. Unlike sine waves, square waves have many harmonics above their fundamental frequency. The monitor transmits on tenth (100MHz) harmonics of the square wave. Use a quarter-wave 75cm piece of wire for the antenna.

Fig. 3: Component layout of the PCB

The audio section of the transmitter is built around IC1. The gain is set to 200 by capacitor C2. Audio from electret microphone MIC1 is picked up and amplified by LM386. It is then coupled with varactor diode D1 via resistor R2. The crystal’s frequency along with D1 forms an FM modulation signal. Since the circuit transmits on tenth harmonic of crystal frequency, audio deviation is also multiplied by a factor of 10. This results in clear audio that can be received on an FM receiver.

Construction and testing
An actual-size, single-side PCB for the baby monitor circuit is shown in Fig. 2 and its component layout in Fig. 3. Keep all leads as short as possible. After assembling the circuit on a PCB, enclose it in a suitable plastic box. Drill a small hole for the microphone. Use 12V to power the circuit. The current consumption of the circuit is very low. Before using the circuit, ensure that power supply is correct.

Sourced By : EFY

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An Electronic Watering Can Circuit Diagram

An Electronic Watering Can Circuit Diagram. Summertime is holiday time but who will be looking after your delicate houseplants while you are away? Caring for plants is very often a hit or miss affair, sometimes you under-water and other times you over-water. This design seeks to remove the doubt from plant care and keep them optimally watered. 

The principle of the circuit is simple: first the soil dampness is measured by passing a signal through two electrodes placed in the soil. The moisture content is inversely proportional to the measured resistance. When this measurement indicates it is too dry, the plants are given a predefined dose of water. This last part is important for the correct function of the automatic watering can because it takes a little while for the soil to absorb the water dose and for its resistance to fall. If the water were allowed to flow until the soil resistance drops then the plant would soon be flooded.

An Electronic Watering Can Circuit Diagram

 

An Electronic Watering Can Circuit Diagram

The circuit shows two 555 timer chips IC1 and IC2. IC1 is an astable multivibrator producing an ac coupled square wave at around 500 Hz for the measurement electrodes F and F1. An ac signal reduces electrode corrosion and also has less reaction with the growth-promoting chemistry of the plant. Current flowing between the electrodes produces a signal on resistor R13. The signal level is boosted and rectified by the voltage doubler produced by D2 and D3. When the voltage level on R13 is greater than round 1.5 V to 2.0 V transistor T2 will conduct and switch T3. Current flow through the soil is in the order of 10 µA. 

T2 and T3 remain conducting providing the soil is moist enough. The voltage level on pin 4 of IC2 will be zero and IC2 will be disabled. As the soil dries out the signal across R13 gets smaller until eventually T2 stops conducting and T3 is switched off. The voltage on pin 4 of IC2 rises to a ‘1’ and the chip is enabled. IC2 oscillates with an ‘on’ time of around 5 s and an ‘off’ time (adjustable via P2) of 10 to 20 s. This signal switches the water pump via T1. P1 allows adjustment of the minimum soil moisture content necessary before watering is triggered. 

The electrodes can be made from lengths of 1.5 mm2 solid copper wire with the insulation stripped off the last 1 cm. The electrodes should be pushed into the earth so that the tips are at roughly the same depth as the plant root ball. The distant between the electrodes is not critical; a few centimetres should be sufficient. The electrode tips can be tinned with solder to reduce any biological reaction with the copper surface. Stainless steel wire is a better alternative to copper, heat shrink sleeving can used to insulate the wire with the last 1 cm of the electrode left bare. Two additional electrodes (F1) are con nected in parallel to the soil probe electrodes (F). The F1 electrodes are for safety to ensure that the pump is turned off if for some reason water collects in the plant pot saucer. A second safety measure is a float switch fitted to the water reservoir tank. 

When the water level falls too low a floating magnet activates a reed switch and turns off the pump so that it is not damaged by running with a dry tank. Water to the plants can be routed through closed end plastic tubing (with an internal diameter of around 4 to 5 mm) to the plant pots. The number of 1 mm to 1.5 mm outlet holes in the pipe will control the dose of water supplied to each plant. The soil probes can only be inserted into one flowerpot so choose a plant with around average water consumption amongst your collection. Increasing or decreasing the number of holes in the water supply pipe will adjust water supply to the other plants depending on their needs. A 12 V water pump is a good choice for this application but if you use a mains driven pump it is essential to observe all the necessary safety precautions. 

Last but not least the electronic watering can is too good to be used just for holiday periods, it will ensure that your plants never suffer from the blight of over or under-watering again; provided of course you remember to keep the water reservoir topped up…

Author : Robert Edlinger

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Railway Points Sequencer Circuit Diagram

Dedicated model rail enthusiasts using sophisticated train and points controllers often have the problem that as their layouts get bigger and more complex, the transformer supplying power to the points does not have enough current to switch several points at the same time. The actuators in the points are designed for ac operation so it doesn’t help by rectifying the supply and adding reservoir capacitors, the coils can overheat and burn out if they get jammed during their travel (ac operation actually helps to overcome friction in the mechanism). The circuit shown here solves this problem by using a sequencer to ensure than only one points actuator can be active at any point in time. During operation the controller will switch all the points on one line at the same time as usual, but the other connection to each coil is connected to the sequencer unit. This circuit will only allow current to flow through one coil at a time.

The sequencer circuit consists of a 555 timer configured as an astable multivibrator clocking a 4017 Johnson counter where the ten outputs are used to switch ten triacs in sequence, enough for ten sets of points. P1 alters the oscillator frequency of the 555 timer and can be adjusted so that each time interval of the sequencer is long enough to allow the points to switch. 

Railway Points Sequencer Circuit Diagram

The switching time varies depending on the type of points but is typically between 1 s and 1.5 s. Any points that jam during switching give out a characteristic humming noise in time to the switching frequency so it makes them easier to find. The eleventh output of the 4017 can be connected to an LED (together with a series resistor). This will flash to give a visual indication of the sequencers operation. Power for the circuit is provided by 15 V ac from the points transformer. The B80C1500 bridge rectifier (80 Vpiv, 1.5 A) and regulator IC1 produce a stabilised 12 V for the circuit. Current consumption is only a few milliamps.

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LED Clock Using PIC 11

Now you'll be able to perpetually grasp the precise time. With this style you'll be able to have an atomic clock in your area. Isn’t that great? scan on to grasp additional.

First of all, it's not regarding any radioactive components here. this can be regarding building a clock show that may get the time from the DCFF77 facilities in Frankfurt, Germany.All that's required may be a clock LED show, DCFF77 receiver, and a microcontroller at the side of the mandatory connections.

Basically, the project permits a sign that's sent by the DCFF77 radio station to be decoded. After that. the microcontroller method it and sends it to the LED show to indicate the precise time. there's no got to build a sign receiver, an honest quality receiver may be bought on the net for a coffee worth.

Once everything has been set within the affiliation board the PIC supply code ought to be developed. The orientation of the antenna ought to be perpendicular to Frankfurt. it'll receive signal if it's among 2000 miles from town. If there's a sign, the amount on the clock LED show can blink during a constant rhytm. When a full cycle of binary pulses is received, the clock can show the precise time.

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Garage Door Closing Circuit Just using Relays

Because I’m old school, I wanted to build a Garage Door Closing circuit without relying on integrated configurations (555 timer etc) to keep it simplistic. The circuit closes the garage door after two minutes with C3 and four minutes with the addition of C2. The timer relay is surprisingly accurate (+/- five seconds). Another feature is to ensure that the garage door actually did close, such as if it’s stopped mid-operation by the user.

S3 (magnetic N.C.) is located at the garage door and activates the circuit when the garage door opens.

RL1 is the reset timer. It’s maintained in the “on” position for two minutes by C3 while the trigger capacitor, C4, is charged. RL2 is the conduit, directing C4 to either RL3 or R1 to ground when off. Purpose of R1 is to prevent arching across contacts and a fast discharge. RL3’s contacts are connected to the Garage Door’s Momentary Switch and is sustained “on”  for a half second by C5.

When C3 discharges to the cutoff voltage of RL1, it turns off and resets. C4 charges C5, which turns on RL3 and initiates the garage door. Because C4 does not have the time to fully discharge, it should be at least three times the value of C5. If it does not close, RL1 in countdown mode will reset and open the door. When it resets again, the door will close.

Turning off the circuit, C1 maintains RL1 “on” slightly longer to ensure that RL2 is set to discharge C4 to R1. If this is not done and C4 is not discharged, the garage door will not open until it discharges naturally and falls below the trigger voltage for RL3.  The circuit would be useless for several days.

Notes:

• Time delay of RL1 after reset drops 15 seconds because of the short charge time.
• To boost RL3 to a one-second delay, increase C5 to 1000uF.
• D2, D3, and D4 isolate the crucial sections of the circuit.
• Relays do not turn off at the same rate. I conducted a test by tripping the circuit on and off at a high rate and discovered the possibility of C4 turning on RL3. The addition of C1 solved this.

Author: Roland Segers (speedmail-at-gmail.com)

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12KV High Voltage Generator Circuit Diagram

This is the simple 12KV High Voltage Generator Circuit Diagram. The hobby circuit below uses an unusual method to generate about 12,000 volts with about 5uA of current. Two SCRs form two pulse generator circuits. The two SCRs discharge a 0.047uF a 400v capacitor through a xenon lamp trigger coil at 120 times a second.

12KV High Voltage Generator Circuit Diagram

The high voltage pulses produced at the secondary of the trigger coil are rectified using two 6KV damper diodes. The voltage doubler circuit at the secondary of the trigger coil charges up two high voltage disc capacitors up to about 12KV. Although this circuit can’t produce a lot of current be very careful with it. A 12KV spark can jump about 0.75 of an inch so the electronic circuit needs to be carefully wired with lots of space between components.

Source: DiscoverCircuits

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Improvised Fan Grills

Making your own grill for your fans would be a lot easier and cheaper. You could use all materials that can be found in your home.

Your main component would be your old fan, removed its metal ring and you can now measure the desired length or size of grid that you will be needed. Cut the grid across so it will be easier to cut, then place it in the tower and use the same screw you removed in the fan.

Now you can put the grid holding fan back in its place. Clean up and you can now use your very own fan grills that cost almost nothing but your patience.

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Low-Cost Arduino Thermal Camera

Do you still remember the H1N1 outbreak in Asia? The manifestations are usually flu-like symptoms which includes fever, cough and colds. The best way to detect fever when people are arriving from the affected areas was to use a thermal camera. These were widely used in Asian countries especially on airports but not all can afford one because it’s very expensive.

We can all agree that this is the greatest deal ever! A thermo-cam which costs around 100$, now there is no reason it can’t be bought by even poor countries to help prevent the spread of the disease. Credit must be given to inventions like this because it’s really a big help.

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Whistle Responder Project

20 years ago it was common to see small key-holders emitting an intermittent beep for a couple of seconds after its owner whistled. These devices contained a special purpose IC and therefore were not suited to home construction. The present circuit is designed around a general purpose hex-inverter CMos IC and, using miniature components and button clock-type batteries can be enclosed in a matchbox. It is primarily a gadget, but everyone will be able to find suitable applications.

Circuit operation:

This device beeps intermittently for about two seconds when a person in a range of around 10 meters emits a whistle. The first two inverters contained in IC1 are used as audio amplifiers. IC1A amplifies consistently the signal picked-up by the small electret-microphone and IC1B acts as a band-pass filter, its frequency being centered at about 1.8KHz. The filter is required in order to select a specific frequency, the whistle's one, stopping other frequencies that would cause undesired beeper operation. IC1C is wired as a Schmitt trigger, squaring the incoming audio signal. IC1D is a 2 second-delay monostable driving the astable formed by IC1E & IC1F. This oscillator generates a 3 to 5Hz square wave feeding Q1 and BZ1, thus providing intermittent beeper operation.

Circuit diagram:

Whistle Responder Circuit Diagram

Parts:

R1 = 22K 1/4W Resistor
R2 = 10K 1/4W Resistor
R3 = 4M7 1/4W Resistor
R4 = 100K 1/4W Resistors
R5 = 220R 1/4W Resistor
R6 = 330K 1/4W Resistor
R7 = 47K 1/4W Resistor
R8 = 100K 1/4W Resistors
R9 = 2M2 1/4W Resistor
R10 = 1M5 1/4W Resistor

C1 = 47nF 63V Polyester or Ceramic Capacitors
C2 = 10nF 63V Polyester Capacitors
C3 = 10nF 63V Polyester Capacitors
C4 = 1µF 63V Electrolytic Capacitors
C6 = 1µF 63V Electrolytic Capacitors
C5 = 47nF 63V Polyester or Ceramic Capacitors

D1 = 1N4148 75V 150mA Diodes
D2 = 1N4148 75V 150mA Diodes
Q1 = BC337 45V 800mA NPN Transistor
B1 = 2.8 or 3V Battery (see notes)
IC1 = 4049 Hex Inverter IC
BZ1 = Piezo sounder (incorporating 3KHz oscillator)
MIC1 = Miniature electret microphone

Notes:

• Power supply range: 2.6 to 3.6 Volts.
• Standing current: 150µA.
• Depending on dimensions of your box, you can choose from a wide variety of battery types:
• 2 x 1.5 V batteries type: AA, AAA, AAAA, button clock-type, photo-camera type & others.
• 2 x 1.4 V mercury batteries, button clock-type.
• 1 x 3 V or 1 x 3.6 V Lithium cells.

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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 Earth's 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.

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Automatic Water Tank Filler Circuit Diagram

This circuit has been very useful in filling a header tank for a reticulated water supply on a farm. Eight troughs are supplied in different paddocks where a lack of water would have serious consequences for the stock. In the past, the tank had been filled daily by a time clock which was not successful. During hot weather, the stock would empty the tank on a regular basis and then be without water for several hours or the tank would overflow and flood the area if the weather was wet and the cattle did not drink much.1

 Circuit Diagram:

Automatic Water Tank Filler Schematic Circuit Diagram

The circuit described has been used to maintain the level of water in the header tank within prescribed limits. It controls a 3HP submersible bore pump which has a high starting current, necessitating a solid-state relay sufficient to take the starting load. Two Darlington transistors, Q1 & Q3, in conjunction with Q2 & Q4, are connected to the upper and lower water sensors in the tank. Q2 & Q4 have a common 5.6kO load resistor and function as a NOR gate. The output of the NOR gate drives Q5 which activates relay RLY1.

 Initially, when the water level is low, both sensors will be open-circuit, the NOR gate output will be high and the relay will be turned on. This causes the normally closed (NC) contacts of the relay to open and disconnect the lower sensor. However, the upper sensor will still be open circuit and the NOR gate output will be high, keeping the relay closed. The normally open (NO) contact of the relay will be closed to operate the solid-state relay RLY2 to run the pump.

This state continues until the water reaches the top sensor which will then drop the output from the NOR gate to 0V. The disables relay RLY1 and the pump is stopped. In practice the upper level sensor is just below the overflow from the tank and the lower sensor about half way up the tank. The sensor contacts are simply two stainless steel screws about 25mm apart and screwed through the poly tank walls. The wiring junctions on the side of the tank are protected by neutral-cure silicone sealant.

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Traffic Interactive Educational Circuit Diagram

This is a circuit of an educational interactive traffic, it uses a single Schmitt-trigger inverter IC (IC1a-IC1f) to directly drive three LEDs (red, green and yellow). When you call, the circuit turns red for 30 seconds, then green for 6 seconds, then yellow for 3 seconds, then repeats the sequence.

Interaction of Light is provided by S1 which shortens the red to a period of just over 3s, if pressed while red is on.

Traffic Interactive Educational Circuit Diagram

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Muscular Bio-Stimulator for Treatment of Cellulite Circuit Diagram

This is a very simple circuit of a bio-stimulator Muscular, which has indications for the treatment of cellulite. He sends little shocks through two electrodes, and should take great care when using the stimulator. The muscle stimulator circuit is based on a 555 timer IC. The transformer must be 220 volts to 12 100 to 150 mA and the circuit is connected in reverse.

Muscular Bio-Stimulator for Treatment of Cellulite Circuit Diagram

The IC 555 to generate pulses at 80 Hz and 150usec by the output voltage of the muscle stimulator device is about 60 volts to 150 volts, but the output current is very small and there is no danger of electric shock.

The potentiometer P1 bio-stimulator sets the amplitude of the output pulses' and must be operated by the "patient", starting with the knob fully counterclockwise, then rotating it slowly clockwise until the LED begins to light up.

The functional principles of the bio-stimulator is the same commercial bio-stimulator.

Parts List:

Linear Potentiometer P1 4K7
R1 180K 1/4W Resistor
R2 1K8 1/4W Resistor
R3 2K2 1/4W Resistor
R4 100R 1/4W Resistor
C1 100nF 63V Polyester Capacitor
C2 100uF 25V electrolytic capacitor
D1 Red LED 5mm.
D2 1N4007 1000V 1A Diode
Q1, Q2 BC327 45V 800mA PNP Transistors
IC1 CMOS 555 timer IC
T1 220V Primary, 12V Secondary 1.2VA current transformer
B1 3V (two 1.5V AA or AAA)

Muscular Bio-Stimulator for Treatment of Cellulite Circuit Diagram

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EE-ternal Blinker Circuit Diagram

You occasionally see advertising signs in shops with a blinking LED that seems to blink forever while operating from a sin-gle battery cell. That’s naturally an irresistible challenge for a true electronics hobbyist. And here’s the circuit. It consists of an astable multivibrator with special proper-ties. A 100-µF electrolytic capacitor is charged relatively slowly at a low current and then discharged via the LED with a short pulse. The circuit also provides the necessary voltage boosting, since 1.5 V is certainly too low for an LED. 

EE-ternal Blinker Circuit Diagram

The two oscillograms demonstrate how the circuit works. The voltage on the collector of the PNP transistor jumps to approximately 1.5 V after the electrolytic capacitor has been discharged to close to 0.3V at this point via a 10-kΩ resistor. It is charged to approximately 1.2 V on the other side. The difference voltage across the electrolytic capacitor is thus 0.9 V when the blink pulse appears. This voltage adds to the battery voltage of 1.5 V to enable the amplitude of the pulse on the LED to be as high as 2.4 V. However, the voltage is actually limited to approximately 1.8 V by the LED, as shown by the second oscillogram. The voltage across the LED automatically matches the voltage of the LED that is used. It can theoretically be as high as 3 V. 

The circuit has been optimised for low-power operation. That is why the actual flip-flop is built using an NPN transistor and a PNP transistor, which avoids wasting control current. The two transistors only conduct during the brief interval when the LED blinks. To ensure stable operating conditions and reliable oscillation, an additional stage with negative DC feedback is included. Here again, especially high resistance values are used to minimise current consumption. 

The current consumption can be estimated based on the charging current of the electrolytic capacitor. The average voltage across the two 10-kΩ charging resistors is 1 V in total. That means that the aver-age charging current is 50 µA. Exactly the same amount of charge is also drawn from the battery during the LED pulse. The average current is thus around 100 µA. If we assume a battery capacity of 2500 mAh, the battery should last for around 25,000 hours. That is more than two years, which is nearly an eternity. As the current decreases slightly as the bat-ter voltage drops, causing the LED to blink less brightly, the actual useful life could be even longer. That makes it more than (almost) eternal.

Author : Burkhard Kainka

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How to Make your own Breadboard

Often we do not have the opportunity or the money to keep our hobby, sometimes we lack tools, but always there is a knack for everything, is what we see here in this article was originally published at indestructible. He teaches you how to make your own breadboard using scrap old computers, in fact it uses sockets IDE cable. The breadboard makes life easier for those who like to create electronic circuits, and can only plug components without using solder.

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Simple Quiz Circuit Diagram

This is the Simple Quiz Circuit Diagram. I've had a few requests for a quiz circuit, so here is a 4 input design which can easily be modified. Maybe, I should write the application notes in the style of a game show host...

Circuit diagram

Notes:
This design uses four IC's and has four input circuits and four independent outputs and a single master reset switch. The outputs here are LED's but may be modified to drive lamps or buzzers. Only one output LED can be lit at any time. The first person to press their input switch, A,B,C,D will light the corresponding output LED, disabling the other inputs.

The circuit uses all CMOS IC's part numbers shown on the diagram. The supply voltage may be anything between 3 and 15 volts. Alternatively, it may be built using equivalent TTL IC's and powered on 5 volts. The main component in this circuit is a bistable latch, here it is based on the dual 4013 D-type flip flop.

Circuit Operation:
Pressing the reset switch will clear all flip flops and extinguish any lit LED's. Under this condition the Q outputs will all be low (logic 0) and NOT Q outputs will be high (logic 1). All four NOT Q outputs are fed to a 4 input AND gate, the 4082 whose output will also be high. The output of the 4082 is wired to one input of each 2 input AND gate (4081). Switch inputs A,B,C,D are all non latching push button switches, the first person to press their switch will cause the corresponding AND gate (4081) to go high and trigger the preset input of the 4013 D-type flip flop.

This will latch and light the appropriate LED. Also the triggered flip flop will have its NOT Q output, set at low, this changes the 4082 output to low and prevents any further triggering of the other flip flops. Switch contact de-bouncing is not required as the first press will latch one of the bistables. Pressing the reset switch, restores the circuit to its former state. I would recommend using heavy duty push button switches, as in use they are likely to be under some stress. 

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NE566 Function Generator Circuit Diagram

The NE566 Function Generator is a Voltage-Controlled Oscillator of exceptional linearity with buf fered square wave and triangle wave outputs. The frequency of oscillation is determined by an external resistor and capacitor and the voltage applied to the control terminal. The Oscillator CAN be programmed over a ten-to-one frequency range by proper selection of an external resistance and modulated over a ten-to-one range by the control voltage, with exceptional linearity.

 FMAX = 1 MHz     WIDE 1000:1 Continuous Sweep Possible

 NE566 Function Generator Circuit Diagram

Pdf Datasheet 

Sourced by : Circuitsstream

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Simple Suitable AC DC Circuit Diagram

This is a project of Simple Suitable AC DC Circuit Diagram. This circuit is simple, but very useful as well as simple and inexpensive. Its use is simple, when the positive (red) is connected to a positive voltage DC and the black lead on the negative, the red LED lights. Reversing polarities the Green LED lights. Connecting the ends to an AC source both LEDs will light. The lamp current is limited to 40mA LEDs @ 220V AC and its filament is illuminated with approximately 30V, shining more intensely with increasing tension. Therefore, due to the behavior of the filament, any voltage in the range of 1.8 to 230 can be detected without changing component values​​.

Suitable AC DC Circuit Diagram

D1 = 3 mm or 5. red LED
D2 = 3 mm or 5. green LED
LP = 1220V 6W NEON

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Geiger Counter Uses Cockroft-Walton Multiplier Project

This is a project of Geiger Counter Uses Cockroft-Walton Multiplier circuit diagram. The recent tsunami in Japan and the on-going calamity with the Fukushima nuclear power plant has apparently greatly increased sales of radiation meters, not only in Japan but elsewhere around the world. This device will allow an estimation of the level of radioactivity, being sensitive enough for background radiation monitoring or to provide an estimation of the level of radioactivity from sample objects such as Thorium gas mantles in LPG lamps. The circuit is compatible with several Geiger Muller tubes and three types of indication are provided: the good old-fashioned audible click with each discharge, a flashing LED or an analog meter providing a rough average of radiation levels.

Geiger Counter Uses Cockroft-Walton Multiplier Circuit Diagram




A normal background count in New Zealand with the smaller GM LND712 tube is around 30 counts per minute, while the larger and more-sensitive LND7312 pancake tube will count about four times this figure. Both GM tubes will detect alpha, beta and gamma radiation. Unless the tube is “filtered”, there is no way of knowing just what type of radiation is being detected, although a rough guess can be made. Alpha particles will be stopped by placing a sheet of paper between the tube and the source, Beta particles (electrons) will be stopped with a few layers of aluminium foil and the more lively Gamma rays will need a layer of lead.

The circuit provides a regulated 500V supply for the Geiger Muller tube. This voltage places the tube into its linear operating mode so that a discharge inside the tube will occur when a particle enters through the mica window of the tube and causes the gas to ionise. The very short pulse produced is stretched and used to signal that a discharge has occurred. The power supply consists of an oscillator and small transistor driving the 6V secondary of a 240VAC mains transformer. The stepped up output of the transformer is fed to a Cockroft-Walton voltage multiplier consisting of diodes D3-D7 and the associated 47nF 630V metallised polyester capacitors.

IC1 is a 40106 Schmitt trigger inverter and IC1a is connected as an oscillator running at several hundred hertz. This is buffered by IC1b and fed to the base of NPN transistor Q1 which then drives the abovementioned transformer. IC1c acts as an error amplifier to regulate the high voltage fed to the GM tube. A portion of the DC voltage produced at the junction of diodes D4 & D5 is monitored by a voltage divider consisting of the 4.7MO and 47kO resistors, in combination with trimpot VR1. When the voltage from D5 is below the positive threshold of IC1c, its output will be high and IC1a will be able to oscillate. Hence, the oscillator will pulse on and off, to maintain the 500V set by VR1.

Each time there is a discharge in the GM tube, the resultant current triggers the BT149 SCR which discharges the associated 100nF capacitor and thereby acts as a pulse stretcher to drive the three remaining inverters in IC1. These in turn drive a high-brightness red LED (LED1), a piezo transducer and an analog metering circuit which is based on an old VU meter movement with a scale graduated in counts/minute. The current drain of the circuit is 10mA and a small 9V battery should run the counter for many hours. Warning: do not touch the window of the GM tube. These are very fragile and made of very thin mica, to allow the low-energy alpha particles to pass through. With the LND 712, 200 counts per minute is roughly equivalent to 0.3 micro-seiverts.

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Simple Fridge Thermostat Circuit Diagram

This is a simple project of Fridge Thermostat Circuit Diagram. What to do when the thermostat in your fridge doesn’t work any more? Get it repaired at (too) much expense or just buy a new one? It is relatively simple to make an electronic variation of a thermo-stat yourself, while saving a considerable amount of money at the same time. How-ever, be careful when working with mains voltages. This voltage remains invisible and can sometimes be fatal! 

This design allows for five temperatures to be selected with a rotary switch. By selecting suitable values for the resistors (R1 to R7), the temperatures at the various switch positions can be defined at construction time. With the resistance values shown here, the temperature can be adjusted to 16, 6, 4, 2 and –22 °C. 16° C is an ideal temperature for the storage of wine, while 6, 4, and 2 degrees are interesting for beer connoisseurs and the minus 22°degrees position transforms the fridge into a large freezer. Note for wine connoisseurs: to prevent mould on the labels, it is necessary to place a moisture absorber or bag of silica gel in the fridge. 

Fridge Thermostat Circuit diagram :

Fridge Thermostat Circuit Diagram

The circuit is built around an old work-horse among opamps, the 741. D1 pro-vides a stable reference voltage of 5 V across the entire resistor divider. P1 allows adjustment of the voltage at the node of R1 and R2. To use the above-mentioned temperatures as setpoints this voltage needs to be adjusted to 2.89 V. D2 is a precision temperature sensor, which can be used from –40 to +100 °C. The voltage across this diode varies by 10 mV per Kelvin. In this way D2 keeps an eye on the temperature in the fridge. The reference voltage derived from the voltage divider (selected with S1) is com-pared by IC1 with the voltage across the temperature sensor. Based on this, the 741 switches, via the zero voltage crossing driver (IC2), a triac that provides volt-age to the compressor motor. The zero voltage crossing IC switches only at the zero crossings of the mains voltage, so that interference from the compressor motor is avoided when turning on. 

The power supply for the circuit is pro-vided by a simple bridge rectifier and filtered with two electrolytic capacitors of 220 µF each. 

The design can also be used for countless other uses. You can, for example, make a thermostat for heating by swapping the inputs of the opamp.

Keep in mind the safety requirements when building and mounting the circuit.

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