This is a schematic diagram of stereo audio amplifier for your car. The circuit is powered by a single IC TDA1553 with some external components, this IC will handle your stereo car audio system.

The TDA1553CQ is a monolithic integrated class-B output amplifier in a 13-lead plastic DIL-bent-SIL power package. It contains 2×22 W amplifiers in BTL configuration. The device is primarily developed for car radio applications.

The TDA1553CQ contains two identical amplifiers with differential input stages and can be used for bridge applications. The gain of each amplifier is fixed at 26 dB.

Special features of the device are:

3-state mode switch
· standby: low supply current (<100>

Loudspeaker protection
When a short-circuit to ground occurs, which forces a DC voltage across the loudspeaker of >= V, a built-in protection circuit becomes active and limits the DC voltage across the loudspeaker to <= V. Pin 12 detects the status of the protection circuit (e.g. for diagnostic purposes).

Short-circuit protection
If any output is short-circuited to ground during the standby mode, it becomes impossible to switch the circuit to the mute or operating condition. In this event the supply current will be limited to a few milliamps.

Download the TDA1553CQ datasheet

Short circuit protection, 94dB supply rejection ratio, thermal protection, S/N ratio in excess of 100dB, Open loop gain typically 90dB and 70mA quiescent current, LM1875 is great enough to give you good audio performmance. This power IC will amplify the audio signal up to 30W output power.

Component part list

R1 _____________ 1K R2 _____________ 1M R3 _____________ 22K R4 _____________ 10K R5 _____________ 180K R6 _____________ 1R IC1 ____________ LM1875

C1 _____________ 1uF 50V C2,6 ___________ 100nF C3 _____________ 22uF 63V C4 _____________ 0.22uF C7,5 ___________ 220uF 50V Miscellaneous: Fuse holder & cover 2 amp fuses

Visit this 25W Power Amplifier page for detail explanation

Here the simple gate alarm circuit that built based on CMOS IC 4093B. With CMOS IC, this circuit must be work with small universal power supply.

IC1a is a fast oscillator, and IC1b a slow oscillator, which are combined through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, etc.) is opened. The circuit is intended not so much to sound like a siren or warning device, but rather to give the impression: "You have been noticed." R1 and D1 may be omitted, and the value of R2 perhaps reduced, to make the Gate Alarm sound more like a warning device. VR1 adjusts the frequency of the sound emitted.

IC1d is a timer which causes the Gate Alarm to emit some 20 to 30 further pips after the gate has been closed again, before it falls silent, as if to say: "I'm more clever than a simple on-off device." Piezo disk S1 may be replaced with a LED if desired, the LED being wired in series with a 1K resistor.

Figure 2 shows how an ordinary reed switch may be converted to close (a "normally closed" switch) when the gate is opened. A continuity tester makes the work easy. Note that many reed switches are delicate, and therefore wires which are soldered to the reed switch should not be flexed at all near the switch. Other types of switches, such as microswitches, may also be used.

Spurce: http://www.zen22142.zen.co.uk/Circuits/Alarm/Galarm.html

This is a waveform generator based on IC with wide operating frequency, Maxim MAX038. This IC is able to generate frequency between 0.1Hz to 20MHz.

Here the schematic diagram:

• The circuit can be used to generate square wave, triangle, or sine wave by programming the pin inputs (A0:pin 3, A1:pin 4).
  • A0 A1 WAVEFORM
  • X 1 Sine wave
  • 0 0 Square wave
  • 1 0 Triangle wave
• The frequency can be controlled using current. If we disconnect the 20k RIN from REF (pin 1) and connect it to a DAC, then we can control the frequency using microcontroller or digital interface. We can even control the chip using a quartz crystal (PLL) by controlling the current using a phase comparator output that compares the sync output (pin 14 of MAX038) and a reference clock from quartz crystal oscillator.

Just try to build this circuit... :)

This is a circuit diagram of light detector. This circuit can be used as a sensor of automatic lamp switch, thic circuit also can be used for anti theft alarm circuit.

Schematic diagram:

Use variable resistor R1 to adjust the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 to reset the circuit. You may used piezo buzzer or LED as output indicator, you may use both of them.