This simple circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components, so it doesn`t add much in the way of size and cost to a project.
The circuit requires four astable multivibrators for its working. Therefore two 556 ICs are used here. The IC 556 contains two timers (similar to 555 ICs) in a single package. One can also assemble this circuit using four separate 555 ICs. The first multivibrator produces a rectangular waveform with 1-second low duration and 2-second high duration. This waveform is used to control the next multivibrator that produces another rectangular waveform.
This device is a simple timer, allowing to keep on the headlights of your vehicle for about 1min. and 30sec., e.g. when accessing some dark place, without the necessity of coming back to switch-off the lights.
A very regular configuration of the 555 astable timer to work as a timer to trigger an alarm or any other equipment connected to pin 3. R resistor should be replaced with a potentiometer that will change the time delay. Capacitor C should be calculated too (there are many 555 calculators around internet).Is a common design, not very accurate but very usefull in many everyday aplications.
This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared by IC2A & IC2B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, IC3 is reset and restarts its counting. Pin 2 of IC3 remains in the low state, the two...
This is an infrared gate with two sensors planned to use in the wall in the way behind a door. It can be applied in a toilet to keep track of that someone is inside exceeding a certain amount of time. After that time elapsed, the circuit triggers the digital output wich can turn on a ventillator. The time period the output is turned on can be separately controlled by a second timer.
The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and emitter and the transistor switches on. A larger current flows in the collector circuit enabling the 555 osillator to sound.
This circuit was developed since a number of visitors of this website requested a timer capable of emitting a beep after one, two, three minutes and so on, for jogging purposes.
As shown in the Circuit diagram, SW1 is a 1 pole 9 ways Rotary Switch. Setting the switch in position 1, the Piezo sounder emits three short beeps every minute. In position 2 the same thing happens after a 2 minutes delay, and so on, reaching a maximum interval of 9...
The simple and inexpensive circuit in Figure 1 monitors the liquid level in a container. The piezo crystal, carefully mounted at the bottom surface of the container, receives it activation from the 74HCT14 hex Schmitt trigger. The crystal generates stable clock pulses according to its specification (for example, 6.14 MHz) when it is in free air. The crystal-based clock drives the 0th counter in an 8254 programmable-counter/timer chip,...
Forget to turn off the ceiling fan in your bathroom? Install the simple timer in Figure 1. It`s located out-of-sight in the fan unit, and you turn it on via the wall switch. The circuit costs virtually nothing, using "junk" parts. When ac power appears, a simple rectifier develops approximately 7V across filter capacitor C. This voltage powers the LM2905 analog timer and simultaneously triggers it via trigger-input Pin 1; output Pin 7 then...
This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table).
Many embedded-microcontroller applications require generation of analog signals. An integrated or stand-alone DAC fills the role. However, you can often use PWM signals for generating the required analog signals. You can use PWM signals to create both dc and ac analog signals. This Design Idea shows how to use a PWM timer to simultaneously create a sinusoid, a ramp, and a dc voltage.
The aim of this project was to get a digital camera into a small electric radio controlled (RC) aeroplane and still have it fly. The aeroplane shown, a park flyer, weighs between 400 and 550 grams depending on the size of battery and wing configeration that I use.
I had a Basic Stamp project that needed to measure a nominal 12 volt battery, and I wanted a simple solution. This is the simplest I could come up with. The 555 timer will put out positive pulses. The pulse width is inversely proportional to the difference in voltage between the voltage at "ANALOG IN" and the voltage of the 4.7uF capacitor(let`s say 2.5 volts). To calibrate this circuit, hook it up to a Basic Stamp measuring positive pulses,...
This application note uses a timer IC (ICL7555), CMOS logic and discrete transistors to automatically control the conversion the MAX190 12-bit SAR analog-to-digital converter (ADC). The delay between conversions can be programed using a resistor. Logic circuits ensures proper startup when power is applied.
Most A/D-conversion techniques use dedicated hardware, usually a single-chip IC. The flexible conversion technique allows you to use successive-approximation, ramp-type, or other converters by writing the appropriate control software. The design in Figure 1 uses a PC`s parallel port for interface to a DAC and a special BIOS interrupt (INT 1CH) for the conversion process. The INT CH hardware interrupt is available in all PCs. It automatically...
Figure 1 shows the classic way to use a backlight-driver IC to provide dimming. By modulating an external PWM signal, the circuit controls the white-LED current. By adjusting the on/off-time ratio, or duty cycle, the circuit can provide drive ranging anywhere from full-on to full-off. This circuit relies on the fact that the baseband or application processor has a PWM timer available. A second method of obtaining dimming is to use an...
I don`t know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because at my local electronics store they are over $4 Cdn. Instead, an oscillator made up of two sections of a 4011 NAND gate is employed. This chip is very inexpensive and extremely common.
The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11).
A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use...
Electromechanical door chimes can enhance your home, but they are vulnerable to costly repair problems. A defective pushbutton switch or a careless visitor can maintain the chime in an energized state for a prolonged period, thereby damaging the chime. The circuit in Figure 1 prevents damage to the chime and improves the chime`s effectiveness by repeating the chime strike for as long as the pushbutton remains depressed. The circuit controls...
A time delay relay is a relay that stays on for a certain amount of time once activated. This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use.
Li-Ion batteries are normally charged with a current
limited constant voltage for a fixed length of time. At the
end of this time period, the voltage must be removed to
prevent internal chemistry changes in the battery. At a
minimum, a timer is needed to terminate the charging
process after the maximum amount of time required to
fully charge the battery.
The charger is based on the LTC4053a standalone
timer-terminated constant current/constant voltage linear
charger. The LTC4053 features a thermal loop which
maximizes the charging rate under all conditions by
regulating the maximum die temperature. Less sophisticated
linear chargers must run lower charging rates or
risk overheating, thus increasing charge times.
Picured in Figure 1 is a miniature magnetic gun. When optimally tuned, it will propel a small slug about 1.5 metres high, or 2.5 metres horizontally.
IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to TR4, which fire electromagnets L1...
This 555 timer based PWM controller features almost 0..100% pulse width regulation using R1, while keeping the oscillator frequency relatively stable. The frequency is dependent on values of R1 and C1, values shown will give a frequency range from about 170 to 200 Hz. Any 555 chip will do, CMOS is fine as well. Diodes are not critical, I used 1N4148. Total cost of parts is about $2.
Figure 2 is a diagram of the control circuit
built on a 1.45 X 1.8 inch PC board. IC1 is
an LMC555 CMOS timer that generates a
200 microsecond wide clock pulses to step
the motor and control its speed. The speed
can be varied by changing the pulse
repetition rate with R1.
This Design Idea offers a solution to the challenge of turning devices on or off in the past. In Figure 1, IC2 is a 555-type timer (preferably CMOS) connected as a monostable one-shot multivibrator. The pushbutton switch, S1, triggers IC2. You can replace S1 with a transistor or an optocoupler, for example. You can connect VOUT to a relay or a transistor, if needed. You might need to adjust the values of R4 and R5, depending on the output...
Typical circuit representative of those used in most light switch type digital timers. The timer module is normally a PIC or custom chip, and it syncs to the AC line so that a trigger pulse can be supplied at the right moment.
The drawings and photos below are for an operating incline railway that was built by the London Model Railroad Group for its `O` scale model railway club located at London, Ontario, Canada. This is a single car model loosely based on a double car incline that operated at Port Stanley, Ontario.
The mechanism is driven by a geared slow speed motor and controlled by an electronic timer circuit. The car waits for a preset time at the top and...
Eight LED`s are used to indicate the pad currently selected. These LED`s are connected to a decade counter, which sequences the LED`s when it receives a clock pulse.Only one LED can be lit at a time from the decade counter, so although this circuit contains many LED`s only a small drain us placed on the battery. The clock pulse for the decade counter is generated by a 555 timer.
If you are interested in model aeroplanes and have the capital, a radio controlled electric park flyer is a must have. An RC aeroplane under 400 grams floats around like the rubber models of my youth and contact with the ground doesn`t seems to involve that sickening crunch that comes with larger models. Finding a deserted park in which to fly one (that propellor can still be dangerous) and waiting for a windless day isn`t always that easy...