Circuit-Zone.com - Electronic Projects
Posted on Thursday, March 24, 2011 • Category: Test and Measurement
The ESR Meter is basically an AC Ohmmeter with special scales and protective circuitry. It provides a continuous reading of series resistance in electrolytic capacitors. It operates at 100 kHz to keep the capacitive reactance factor near zero. The remaining series resistance is due to the electrolyte between the capacitor plates and indicates the state of dryness. Capacitor termination problems also show up plainly due to the continuous ohmic reading. The ESR meter uses 8 operational amplifiers. An op-amp is an idealized basic amplifier with two inputs. The non-inverting input (+) has an in-phase relationship with the op-amp output, and the inverting input (-) an out-of-phase relationship. Op-amps are usually used with negative feedback and reach a stable operating condition when their two inputs are equal in voltage.
Op-amps IA & 1B form a regenerative 100 kHz oscillator circuit. Capacitor C1 is the basic timing capacitor and RI is selected to set frequency. Diodes D2 & D3 clip the bottom and top of the output waveform so that the output level and frequency are resistant to battery voltage changes.
Posted on Thursday, March 24, 2011 • Category: FM Transmitters
The FM telephone circuit is built on a PC board that is so small it can easily be fitted inside the housing of a telephone making it an instant pseudo-speak earphone. This FM transmitter circuit connects in series with telephone line, steals power from it, and transmits both sides of the conversation to an FM radio tuned between 90 and 95 MHz.
Posted on Wednesday, March 23, 2011 • Category: Audio Attenuators
Digital potentiometer with memory is a built around PIC 16F819 microcontroller that reads analog resistances, records them to memory and plays them back via digital potentiometer DS1267 chip. The memory buffer size and the playback speed can be adjusted.
Posted on Wednesday, March 23, 2011 • Category: Miscellaneous
This simple lamp dimmer uses only a Triac, a Diac and some other passive components to achieve power control on lamp . It is suitable for 230V incandescent lamps with a total power of up to 300 Watts. At first triac TR1 is not conducting; C1 is charged through R1/P1 until the trigger level of diac D1 is reached. When the diac trigger level is reached (about 30 V), D1 fires and Triac TR1 is switched on. The triac will remain in conductive mode until the mains current is lower than the triac hold current at the end of the half mains period. This works for both the negative and positive mains period because both the triac and the diac are bi-directional. R1 is added to protect the potentiometer in the case of a short circuit. The fuse is absolutely mandatory as the discharge arc in a failing incandescent lamp is virtually a short circuit.
Posted on Wednesday, March 23, 2011 • Category: USB Circuts
Sometimes you just need to connect some device to COM port, but computer don’t have one especially laptop. There are two ways â€“ go and buy USB â€“ COM adapter or build one. So if you decided to build USB to COM(RS232) adapter, there is one of solutions.
This adapter is very easy to build as there is single chip USB to UART bridge (CP2102) used. This chip from Silicon Labs support USB2.0 full speed, has internal Resistors required for USB interface, integrated clock, internal 1024 -byte EEPROM for vendor ID, Product ID serial number, power descriptor and other information. SP2102 USART part support almost all standard features of RS232 communication including handshaking, Databits (5, 6, 7 and 8); 1 or 2 stop bits; odd, even, mark, space and no parities; baud rate from 300bps to 1Mbits.
Device is powered from USB port and requires about 10mA. Chip drivers enable to connect this adapter to most of Operation systems like Win98, Win2000, WinXP, Linux.
Circuit-Zone.com © 2017. All Rights Reserved.