Vacuum Tubes Valves
Musical & effects
Yagi Uda Antennas
Metal Detector Circuits
Liquid Sensing Circuits
Light Sensing Circuits
Voltage Detector Circuits
Air-Gas Detection Circuits
Human Sensing Circuits
RF & Radiation
Optical Sensing Circuits
Free Energy Circuits
AC to DC & DC to DC
Solar Cell Circuits
Micro Power Circuits
Switching Power Supplies
Light Laser LED
Digital to Analog
Analog to Digital
Data Bus Circuits
Voltage to Pulse
Current to Voltage
Frequency to Voltage
RF Converter Circuits
Sine to Square Wave
Voltage to Current
voltage to frequency
Period to Voltage
Video Wall circuits
TV Video Circuits
Motor Control Circuits
8051 / 8052
PCB CAD Software
Car bike Circuits
555 Timer Circuits
Remote Control Toy
H Bridge Circuit
DIY HV Variable Cap
DIY PMA alternator
Interconnection & Timing
Digital Signal Integrity
Digital & Bipolars
Sensors & Detectors
Regulated Power Supply
4 Band Resistor
5 Band resistor
6 Band resistor
LED Driver with Integrated Switches & Schottky
Linear Technologys LT®3466 is a dual step-up converter capable of driving up to 20 white LEDs with a programmable constant current. The device is also capable of driving asymmetric LED strings with independent dimming and shutdown control for multipanel LCD backlight applications.
Low-power keypad 100 nA
The circuit in Figure 1 is a keypad interface that solves this problem by using an ultralow-power microcontroller. The circuit typically consumes 100 nA while awaiting a key press and consumes a maximum of only 2 µA if all keys are stuck or held down. An added bonus of the circuit is that it requires no crystal.
Lightning Activated Camera Shutter Trigger
This circuit is used to trigger a camera`s electronic shutter circuit when a flash of lightning is present. This circuit would also work for photographing fireworks displays or other events involving flashes of light.
pushbutton electronic-potentiometer system
As systems grow smaller, it becomes increasingly attractive to replace mechanical potentiometers with electronic potentiometers, which are smaller and less expensive silicon equivalents. A common interface for such devices comprises a Chip-Select, Increment and, Up/ line. CS activates the device and, on a rising edge of steps the wiper in a...
Analog switch expands I2C interface
The dual-channel PCA9540 I2C multiplexer often breaks up an I2C or SM bus or allows you to use devices with the same addresses on the same bus. When the PCA9540 initially powers up, it comes up in a state in which both channels are deselected. The I2C- or SM-bus master can then address the control register in the PCA9540 to select either Channel...
Analog switch lowers relay power consumption
The circuit lowers this dissipation after actuation by applying less than the normal 5V operating voltage. Note that the voltage required to turn a relay on the pickup voltage is greater than the pickup voltage required to keep in on the dropout voltage. The relay in Figure 1 has a 3.5V pickup voltage and a 1.5V dropout voltage.
Digital Timer Light Switch
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.
Protected Load Management Switch
In an effort to conserve energy, simple shutdown schemes are incorporated into many battery-operated circuits. Not all circuits lend themselves to direct control, however, and instead the supply must be turned off by a switch. The LTC®1477 high side switch is designed for this purpose and includes short-circuit current limit and thermal...
PCMCIA Socket Voltage Switching
Most portable systems have built-in PCMCIA sockets as the sole means of expansion. The requirements of the PCMCIA specification have led to some confusion among system designers. This Design Note will attempt to lessen the confusion and highlight other practical system issues.
Scheme improves on low-cost keyboard
You can easily improve on a previous Design Idea to produce a slightly simpler resistor arrangement with better timing balance between switches, using a single resistor value (Reference 1, Figure 1). The use of a single resistor value, RS, in a series chain for the switch resistors gives the timing parameters a simpler format and should reduce...
Scalable latch requires no capacitors or clock
Circuits that latch one-of-N switches usually use a digital approach. Such circuits are often useful in human-interface situations, such as audio-mixing consoles, video-feed selection, or current-loop-control redundancy systems. In high-precision analog systems, such as high-fidelity audio or video, elimination of clocking circuits, whenever...
digital potentiometer control
Digitally controlled potentiometers are useful for generating analog control voltages under the control of a microcontroller. In some applications, manual pushbutton switches could replace a microcontroller and simplify product design. Mechanical switches exhibit contact bounce, and, when a user actuates them, they may open and close many times...
Microcontroller multiplexes DIP switches
At times, a µC must read a large number of DIP switches, such as for system identification, bus-address setup, manual configuration, or other purposes. However, the available number of I/O lines is sometimes not enough to assign a switch to each one. You can use multiplexer ICs to share one I/O port with multiple switches, but they complicate...
automatic machine shutdown
Some machines need to run for long periods and therefore may finish their work in the middle of the night or during the weekend. For the time remaining, until the operator returns, the machines stay idle, uselessly consuming power. This Design Idea allows a machine to completely shut itself down after finishing its work. In addition, the method...
Interrupt-driven keyboard for MCS-51
Designers of microcontroller-based products that require a keypad for user data entry can select from dedicating an input line for each key, continuously polling the keypad`s x and y lines, or generating an interrupt whenever a user presses a key. Although conceptually simple, dedicating lines to a keypad can tie up most of the microcontroller`s...
Fault-latch circuit protects switchers
Many power-supply designers like to have a regulator latch off in the event of an overcurrent situation or other fault condition. Yet, many PWM controllers do not internally support this latch-off function. Most do, however, have a power-good output and an enable function. The circuit in Figure 1 adds that latch-off capability at low cost in...
VOLTAGE-BASED CONTROLLER FOR SWITCHES
Heres a simple circuit for controlling four switches from a distance through just a pair of wires.
SOLID-STATE SWITCH FOR DC CIRCUITS
This solidstate DC switch can be assembled using just three transistors and some passive components. It can be used to switch on one gadget while switching off the second gadget with momentary operation of switch. To reverse the operation, you just have to momentarily depress another switch.
SMART FOOT SWITCH
Such jobs as jewel cutting and polishing require the workers to switch on/ off two electrical appliances one after another repeatedly for two different services on the same workpiece. This is cumbersome as they need to fully concentrate on delicate handwork on precious jewels. Switching in such situations cannot be done by hand, and...
Soft ON/OFF switch circuit
When the "ON/OFF" button is pressed once, the equipment goes on and stays on. It goes off when the button is pressed again. The circuit is straight forward. It uses a JK CMOS FlipFlop to with its JK terminals tied high to achieve the toggling action. The clock is provided by the push button used for on/off action. The resistor and the capacitor...
This circuit will remove the transient spikes and contact bounces from a non-latching push button switch. Using a 555 timer as a monostable circuit, it is easy to build a good switch debouncer circuit. There are many circuits for SPDT debouncing, but not many for a normally open, push-to-make press button switch (PBS). The 555 monostable gives...
Sound Operated Switch
This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms.
Removing the "DC Thump" from Audio Circuits
You may be familiar with this effect. You switch audio equipment such as an amplifier to a different input and there is a loud click or "thump" in the speaker system. Not all equipment is affected. Some high end audio systems never suffer, but intercoms switching systems are often affected. Most audio outputs have some standing DC voltage which...
The MPF102 (Q1) can be replaced with a NTE451 or ECG451, but still widely available. JFET-N-CHAN, UHF/VHF AMP. The 2N3565 (Q1/Q2) can be replace with a 2N2222(A), BC107, BC108, BC109(A/B/C), NTE123A, or ECG123A. The TIP31 (Q3) can be replaced with a NTE196 or ECG196, but is a common type and widely available. The 'Touch Plate' can be anything...
12V Relay Driver
Dual Channel Relay Board is a simple and convenient way to interface 2 relays for switching application in your project. Input - 12 VDC @ 84 mA. Output - two SPDT relay. Relay specification - 5 A @ 230 VAC. Trigger level - 2 ~ 5 VDC. Berg pins for connecting power and trigger voltage. LED on each channel indicates relay status. Power Battery...
1 button ON / OFF Switch with 555
This project describes how to build a "soft touch" switch. By "soft touch" we mean that you have to push once to set device ON and push again to set device OFF. This kind of switch works by latching a relay to ON state with push of a button and with another push latch is released. It is working like flip-flop states. In that way you can control...
Decoding 4 buttons with two I/O's on AVR
Just the solution for AVR applications in which I/O is tight, such as the ATtiny12. This should work well on other kids of controllers that have independently controlled I/O direction registers, such as PIC and 6805 controllers. This is a solution was devised for those I/O limited 8 pin controllers like the AT90S2323 (though I tested it on an...
USB Printer Chooser Switch
With a DPDT switch, I can switch the two data lines. I tried connecting the shields from the two computers together, the grounds two computers together, switching the D+ and D- lines with the DPDT switch, and leaving the VBus lines float, but for some reason it didn't work. The Lexmark printer seemed to need to see the +5 Volts. It had been many...
Audio Volume Control with Resistor Switches
The traditional potentiometer is implemented with an electrical contact that slides over a resistive layer. An example of a well-known audio-grade potmeter is the Alps Blue. I still use this one myself. A high-end (good and costly) alternative is the rotary switch. This device consists of a series of discrete resistors and switches, of which...
PIC16F627A Touchpad circuit
This board layout was created using the SOIC version of a PIC16F627A without drawing the usual schematic first. Most of the part values are etched on the Layout. The SIP resistor packs I used are 10k ohm, some experimentation with this value may be useful. Three pins are provided for 5 volts, ground, and TTL serial output on a standard...
Greenhouse irrigation controller ( PIC16F84 )
This is a simple one-valve irrigation controller made for our greenhouse. The code contains a software real-time clock (RTC) and a multiplexed 8-digit LED display and keyboard you can use in other projects. The operating software is simple, it contains a real-time clock and a day counter. The valve is turned on in regular intervals in the same...
433 MHz 4-ch receiver with relay output transmitter
Momentary output : One of the relays RE1...RE4 is ON as long as CH1---CH4 is pressed from transmitter. Latch output: when one of channels CH1...CH4 is pressed from transmitter RE1...RE4 are ON as long as other CH is pressed from transmitter. Valid transmission indicator: LED is always on when reciever recieves valid data.
555 Timer Circuits
RC Model Toy Circuits
H Bridge Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
DIY HV Variable Capacitor
DIY PMA Alternator Plans
Digital Signal Integrity