Posted on Sunday, May 22, 2011 • Category: Motor Controllers
Here is a very simple project of controlling a small DC-motor (taken from an old personal cassette player) with ATmega8. The ATmega8 is having three PWM channels, out of which two are used here. PWM waveforms are fed to MOSFET (RFD3055) H-bridge.
Here, direction is controlled using a two-position toggle switch and speed of the motor is controlled by two push-buttons, one for increasing the speed and other for reducing.
The schematic is geiven here (click on the image to enlarge):
When switch SW1 is closed, OC1A channel is active which will feed the PWM signal to Q1 & Q4 MOSFETs. The OC1B pin will remain low keeping the Q3 & Q2 in OFF condition. When SW1 is toggled to open position, OC1A pin will become low, making Q1 & Q4 OFF and OC1B will feed the PWM signal to Q3 & Q2, resulting in the change in the direction of current flow through motor. Hence, motor rotation direction will change.
The speed is controlled by Push-buttons S2 & S3. Pressing S2 will increase the speed in fixed steps. Similarly, pressing S3 will reduce the speed in fixed steps.
Posted on Sunday, May 22, 2011 • Category: Audio DAC
Presented here is high quality USB DAC PCM2906 with built-in headphone amplifier. To see one or more of the same sound card than this is a compact device. That acts as the computer sound card is easy to use. Just plug into a USB port on your computer. It can be used immediately within an IC in PCM 2906 Burr Brown's brand of Neu hear all agree that the sound of course. Used to convert digital signals from the USB port can adjust volume and mute the signal with Noise from the hard drive or CD player can not come to interference. Because a separate circuit from the computer. Add power to drive headphones with a Single Supply OPA2353 Opamp serves as Headphone Amp that does not reconcile the external power supply. This may be an alternative for those who are looking for sound card priced tight, but the quality of glass.
Posted on Sunday, May 22, 2011 • Category: Miscellaneous
This DIY lightning detector circuit is a very sensitive static electricity detector that can provide an early warning of approaching storms from inter-cloud discharge well before an earth-to-sky return strike takes place. An aerial (antenna) formed of a short length of wire detects storms within a two mile radius.
The circuit emits an audible warning tone from a piezo buzzer, or flashes an LED for each discharge detected, giving you advance warning of impendig storms so that precautions may be observed.
Posted on Saturday, May 21, 2011 • Category: Amplifiers
Presented is 68 watts LM3886 Power Amplifier with the use of popular LM3886 amplifier integrated circuit. Amplifier should be fed by source symmetrical good filtered of + 34 and – 34 volts. R2 and L1 is a resistor of 10 ohms / 2watt coiled with 10 to 12 you exhale of enameled thread AWG 20. The circuit integrated lm3886 is a component easy of being found at the electronics stores, for that he is used in several projects of potency audio, some exist circuits with linked lm3886 in bridges for power of up to 150 watts. For most information on the assembly of that circuit, I suggest that sees the datasheet of the lm3886 in the site of the national semiconductors. With the information of the leaf of data you can adapt the circuit with lm3886 your needs.
Posted on Saturday, May 21, 2011 • Category: Oscillators
There is a great deal of old amateur gear which many amateurs have decided to restore and bring back to life. While much of the early amateur transceivers work just fine they usually lack a digital readout and must rely on analog dials for tuning. The problem of dial calibration is complicated by the non-linear effects of tuning capacitors. This month's circuit is a 100Khz crystal calibrator using an inexpensive microprocessor crystal and CMOS IC's which are readily available at Radio Shack.
The main problem with building a 100Khz oscillator is the unavailability of 100Khz crystals. Even if you find a vendor willing to cut such a crystal for you, plan on paying $20 or more not including shipping charges. The circuit uses an inexpensive 8MHz microprocessor crystal which can be easily obtained from most parts suppliers. Using a 74HCT393 binary counter IC, we can easily divide down the 8 MHz signal from our crystal into 100Khz or almost any frequency we need.
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