Matt circuit

Sometimes we forget to switch off the bathroom light and it remains on unnoticed for long periods. This circuit solves the problem of electricity wastage by switching off the lamp automatically after 30 minutes once it is switched on. The back-up LED lamp provided in the circuit turns on for three minutes when mains fails. This is helpful especially when you are taking a shower at night. The circuit is built around binary counter CD4060 (IC2), which has a built-in oscillator and 14 cascaded bistable multivibrators. The oscillator generates clock pulses based on the values of resistors R3 and R4 and capacitor C3. Automatic Bathroom Light with Back-up Lamp Circuit Diagram   For the given values, Q11 output of IC2 goes high after 30 minutes of power-on. Resistor R2 resets the IC for proper operation. The output of IC2 is fed to the gate of the SCR via resistor R6 and LED2, which function as a voltage dropper as well as output status indicator. When the SCR gets gate drive, it fires to...

The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer. A single LED is placed in series with the base of the PNP transistor so that the lower 20 LEDs turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. 40 LED Bicycle Light Circuit Diagram   Adding the LED increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each LED is supplied with about 20mA of current...

Regardless of whether you want to effectively imitate a house fire, a campfire, or light from welding, the circuit described here fills the bill without using a microcontroller, although it does use a larger number of components (including some truly uncommon ones). The circuit is based on three oscillators, which are built using unijunction transistors (UJTs). Each oscillator has a different frequency. The output voltages are mixed, which produces the flickering effect. A unijunction transistor consists of an n-type bar of silicon between two ohmic (non-barrier) base contacts (B1 and B2). The effective resistance is controlled by the p-type emitter region. The designation ‘transistor’ is a somewhat unfortunate choice, since it cannot be used for linear amplification. UJTs are suitable for use as pulse generators, monostable multivibrators, trigger elements and pulse-width modulators. If a positive voltage is applied to the emitter (E), the capacitor charges via the resistor. As soon a...

The article describes a very simple homemade emergency light circuit that can be used during power failures and outdoors where any other source of power might be unavailable. The circuit uses LEDs instead of incandescent lamp, thus making the unit very power efficient and brighter with its light output. Moreover, the circuit employs a very innovative concept especially devised by me which further enhances the economical feature of the unit. We know that LEDs require a certain fixed forward voltage drop to become illuminated and it is at this rating when the LED is at it’s best, that is voltages which is around its forward voltage drop facilitates the device to operate in the most efficient way. As this voltage is increased, the LED starts drawing more current, rather dissipating extra current by getting heated up itself and also through the resistor which also gets heated up in the process of limiting the extra current. If we could maintain a voltage around an LED near to its rated for...

This is basically a Schmitt Trigger circuit which receives input from a cadmium sulfide photo cell and controls a relay that can be used to switch off and on a street lamp at dawn and dusk. I have built the circuit with a 120 ohm/12 volt relay and monitored performance using a lamp dimmer, but did not connect the relay to an outside light. The photo cell should be shielded from the lamp to prevent feedback and is usually mounted above the light on top of a reflector and pointed upward at the sky so the lamp light does not strike the photo cell and switch off the lamp. Photo Electric Street Light Circuit Diagram The photo cell is wired in series with a potentiometer so the voltage at the junction (and base of transistor) can be adjusted to about half the supply, at the desired ambient light level. The two PNP transistors are connected with a common emitter resistor for positive feedback so as one transistor turns on, the other will turn off, and visa versa. Under dark conditions, the ph...

Every year I notice that I have little issue waking up at 7am during summer months, yet waking up at 8am during winter is always unpleasant. Some quick research led me to find that the body is gradually woken up by light, which is why products such as the Phillips Wake-Up Light exist. However, with a starting price of £60 for the (very) basic version, I’ve opted to make my own smartphone-connected, automated wake up light instead. [ ]

This circuit can be used to check, for example, whether the door of a refrigerator has been properly closed. An LED sends out a beam of light, which, if the door is closed, is reflected. An optical sensor (CNY70) then detects the amount of light. If the sensor does not receive the right amount of light, the buzzer will sound after about a minute. When the door is closed (and the CNY70 receives enough light again), the buzzer turns off. Circuit diagram: Reflection Light Barrier with Delay Circuit Diagram The power supply for the circuit requires about 12 mA at 12 V. Potentiometer P1 adjusts the sensitivity of the sensor. The sensor works reliably from a distance of one centimetre. If the current through the LED is increased, the distance can be increased a little. The delay can be adjusted with C3. C4 provides extra filtering for the reference voltage. Thebuzzer would otherwise switch on with a ‘chirping’ sound. The well-known Ne555 is used to drive the buzzer. The buzzer is driven w...

Electronic Components As Light Sensor Electronic components are included in the category of light sensors is LDR, Photo Transistor, Photo Diode, Infrared Receiver. The function of the electronic component is to detect the intensity of light received by the component. The light sensor is often used in electronic equipment such as on television, light a light switch, light intensity measuring instrument. Electronic Components As Light Sensor 

Fig.1 Precision Light- Sensitive Switch Circuit Diagram:   In Fig. 1 see a precision light- sensitive switch that activates when the sensed quantities go above or below pre-set values. The LDR can be any cadmium sulfide unit that has a resistance in the range 500R to 20k at the required trip level. The RV1 adjust LDR at normal light level. Fig. 2 Differential Temperature Switch Circuit Diagram: In Fig. 2 see a differential temperature switch circuit using ordinary silicon diodes as temperature sensing elements and responding to differentials of a fraction of degree. RV2 can be used to apply an effective offset of several degrees to the two diodes. To adjust the circuit, apply the required differential temperature to the diodes and then adjust RV2 so that the relay just turns on. The circuit responds to the relative temperatures, rather than the absolute temperatures, of the two diodes. Part List : R1=LDR *see text R2-3=10Kohm R4=2.2Kohm R5-6-7-10=4.7Kohm R8-9=2.7Kohm RV1=22Koh...

Most PN-junction diodes can be used as photodiodes. While not optimized for this application, they do work. When the diode is reverse biased, it will produce a small photovoltaic output as the light level is increased. LEDs are particularly suited for this task because their housings are transparent. You can construct a simple circuit that will assess the condition of ambient lighting and, because many LEDs’ packages are tinted to enhance their emitted color, may even yield a reasonable evaluation of the detected color. The results are not as effective as those obtained using a high-quality optical filter, which typically has narrow bandpass characteristics, but they can be quite acceptable. Though the design described here does not produce the accuracy of designs with laboratory-grade photodetectors and transimpedance amplifiers, it can be quickly assembled and will produce usable results at a low cost. Three LEDs are used; experimentation will indicate which device has the best sensi...

It’s not often that I finish the various small projects I undertake. Tesla coils, mass spectrometers, automated tomato plant watering systems, homebrew heaters have all been conceived and sometimes parts bought and assembled with some even making it as far as working. This project however made it all the way to finished. [ ]

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800MΩ in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal. Circuit diagram: LED As A Light Sensor Circuit Diagram Resistor R1 ensures that the op amp "sees" a 0V input when the LED is in total darkness. To avoid undue loading of the signal, R1 would ideally be a 100MΩ or larger resistor but since such high values are rare and expensive I used a smaller value and increased the gain of the op amp to compensate for the voltage loss. To avoid the need for a second variable resistor to ...

T his  automatic  bicycle  light  makes cycling in the dark much  easier (although you still need  to pedal of course). The circuit  takes  the  ambient  light  level  into account and only turns on  the light when it becomes dark.  The light is turned off when no  cycling has taken place for over  a minute or if it becomes light  again. The biggest advantage of  this circuit is that it has no manual controls. This way you can  never ‘forget’ to turn the light  on or off. This makes it ideal for  children and those of a forgetful  disposition.   Bicycle Light Image : To detect when the bicycle is  used (in other words, when the  wheels turn), the circuit uses a  reed switch (S1), mounted on  the frame close to the wheel.  A small magnet is fixed to the  spokes (similar to that used with  most  bicycle  speedometers),  which  closes  the  reed  switch  once for every revolution of the  wheel. Whilst the wheel turns,  pulses are fed to the base of T1  via C1. This charges a small el...