two LT1398’s from Linear Technology used to create buffered color-difference signals from RGB (red-green-blue) inputs

The circuit diagram shows two LT1398’s from Linear Technology used to create buffered color-difference signals from RGB (red-green-blue) inputs. In this application, the R input arrives via 75? coax. It is routed to the non-inverting input of amplifier IC1a and to 1.07-k? resistor, R8. There is also an 80.6-? termination resistor R11, which yields a 75-? input impedance at the R input when considered in parallel with R8. R8 connects to the inverting input of a second LT1398 amplifier (IC1b), which also sums the weighted G and B inputs to create a –0.5Y output.
Yet another LT1398 amplifier, IC2a, then takes the –0.5Y output and amplifies it by a gain of –2, resulting in the +Y output. Amplifier IC1a is configured for a non-inverting gain of 2 with the bottom of the gain resistor R2 tied to the Y output. The output IC1a thus results in the color-difference output R–Y. The B input is similar to the R input. Here, R13 when considered in parallel with R10 yields a 75-? input impedance. R10 also connects to the inverting input of ampli?er IC1b, adding the B contribution to the Y signal as discussed above.
Source : www.extremecircuits.net

TLC555 based light to frequency converter circuit

Introduction.

Here is the circuit diagram of a effective light to frequency converter circuit that can be used for variety of applications such as light intensity measurement,fun etc.

The circuit is based on TLC555, the CMOS version of famous timer IC NE 555. A photo diode is used for sensing the light intensity.The timer IC is wired in astable mode.The leakage current of the reverse biased photo diode is proportional to the light intensity falling on it.This leakage current charges the capacitance C1.When the capacitor voltage reaches 2/3 of the supply voltage the out put (pin 3) goes low.As a result the capacitor discharges through photo diode .When the capacitor voltage reaches 1/3 the supply voltage the out put (pin 3) of IC goes high.This cycling continues and we get a frequency at pin 3 proportional to the light intensity falling on the photo diode.

Light to Frequency Converter Circuit Diagram & Parts List.

• With the given components the frequency varies from 1KHZ @ complete darkness to 24 Khz @ bright sunlight.The frequency range can be changed by using different values for C1.
• Use any general purpose photo diode for D1.

S:circuitstoday.com

simplest scheme for converting a CD ROM drive to audio CD player

Description.

Here is the simplest scheme for converting a CD ROM drive of your computer to a Audio CD player.The minimum requirement for the player is that, it should have a audio output and skip button. Luckily most of the Cd ROM’s are equipped with both of these.

The CD ROM drive needs two voltages ,12V & 5V for its operation.So the main objective is to build a suitable power supply for the CD ROM drive.The IC1 (7812) together with associated components produce a regulated 12V DC.The IC2 (7805) together with associated components produce a regulated 5V DC.These voltages as well as ground can be connected to the corresponding voltage pins of the CD ROM drive using a male type CD ROM drive power connector.The 12V can be connected to the yellow wire of connector, 5V to red wire and GND to black wire as shown in figure1.Now the power supply is ready.

Testing.

Make the circuit as shown in the circuit diagram.Power up the circuit after connecting the power connector to the CD ROM drive. Now the power LED of the drive will glow.Insert the audio CD.Now the music will be available at the audio output socket of the drive.It can be heared using a headphone.The skip button of the drive can be used to play next song.

By connecting the audio output to a power amplifier you can enjoy the music in a greater wattage.

Circuit Diagram with Parts list.

• For car stereo applications you don’t need the transformer,rectifier and the 7812 regulator.12V will be available from battery.You just need to produce a 5V from it using a 7805 based regulator. Connect the corresponding voltages to the connector as shown in figure 1 and connect the connector to drive.Done.

• The amplifier for the car audio CD player must be one operating from 12V.

• Do not connect the voltages to CD ROM drive in wrong polarity.Double check the voltages using a multimeter. Wrong polarity could easily damage the drive.

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S:circuitstoday.com

a simple approach for converting a loud speaker into a microphone circuit

This circuit is a simple approach for converting a loud speaker into a microphone. When the sound waves fall on the diaphragm of a speaker, there will be fluctuations in the coil and there will be a small proportional induced voltage. Usually this induced voltage is very low in magnitude and useless. Here in the circuit the low voltage is amplified using transistors to produce a reasonable output. The transistor Q1 is wired in common base mode and produces the required voltage gain. The transistor Q2 is wired as an emitter follower to produce enough current gain. The voice quality of this circuit will not be as much as a conventional microphone but quite reasonable quality can be obtained. To set up the circuit, keep the preset R2 at around 10 Ohms and connect the battery. Now adjust R2 to obtain the optimum sound quality.

NOTES:

• Assemble the circuit on a general purpose PCB.
• Power the circuit from a 9 V PP3 battery.
• A 3 inch speaker can be used as K1.
• All capacitors must be rated at least 15V.
• An 8 Ohm speaker or head phone can be connected at the output to hear the picked sound.

frequency to voltage (F to V) converter

Here is a very simple circuit diagram of a frequency to voltage (F to V) converter. Such a circuit finds numerous applications in projects like digital frequency meters, tachometers etc. The circuit is mainly based on a LM555 timer IC. The IC is wired in mono shot mode to convert the input frequency into a fixed pulse width, variable frequency PWM signal. Resistors R4 and capacitor C2 provides the necessary timing for the circuit. The transistor T1 forms a discharge path parallel to C2 which is necessary for re triggering the IC. Capacitor C1 acts as an input DC decoupler.

• The circuit can be assembled on a Vero board.
• Use 12V DC for powering the circuit.
• LM555 must be mounted on a holder.
• The output of the circuit is not a pure DC but a PWM waveform. Additional circuitry is required to convert this PWM waveform to pure DC.

S:circuitstoday.com

a frequency to current converter circuit (used as tachometer)

Here is a simple circuit that can be used as a tachometer. The circuit is basically a frequency to current converter which converts the incoming signal into a proportional current to drive the meter. The deflection on the ammeter will be proportional to the frequency of the incoming signal. For using this circuit as an automobile tachometer, the input terminal A should be connected to the spark plug cable and terminal B should be connected to the vehicles ground.

For calibrating the circuit, set R2 at 25K and R4 at 5K.Power up the circuit and feed the input terminal with a 60Hz square wave form your function generator. Adjust R2 so that the meter shows 0.36 mA (equal to 3600rpm). Now disconnect the input signal and adjust R3 so that the meter shows 0mA.Now connect the 60Hz signal again and if the meter does not show 0.36mA adjust R4.A completely calibrated circuit will show 0mA at 0Hz and 0.36mA at 60Hz.

• The circuit can be assembled on a Vero board.
• I have not tested this circuit on any automobile. So use this circuit on your automobile at your own responsibility.
• Anyway, the test using the signals from my function generator was satisfactory.
• The ignition voltage from the spark plug terminal is in the Kilo volt rage. The engine must be OFF while making connections and you must be very careful to avoid shock hazards. Try this circuit on your automobile only if you have sufficient knowledge and experience on automobile electricals. I have no responsibility on any mishap.
• The circuit can be powered from 12V DC.
• The bridge D3 can be made using four 1N4007 diodes.
• M1 can be a 1mA FSD ammeter.

S:circuitstoday.com

5v DC from the computer USB port to 12vDC converter circuit

Using this circuit we can convert 5V DC from the computer USB port to 12V DC and a circuit like this will find a lot of application in USB powered systems. The heart of this circuit is IC LT1618 which is a constant current, constant voltage boost converter. The IC has a wide input voltage range of 1.8 to 18V DC and output voltage can be up to 35V DC.

In the circuit resistors R1, R2 sets the output voltage.pin number 9 is the shutdown pin, less than 0.3V to this pin will shut down the IC. Pin number four is the current sense adjust pin. The current sense voltage can be reduced by applying a DC voltage to this pin. If this adjustment is not needed connect this pin to ground and you can omit components R3, R5 and Q1.

Notes :

• C2 and C3 must be rated at least 15V.
• Less than 0.3V at the shutdown pin will shutdown the IC.
• Output voltage is governed by the following equation R1 = R2 ( (Vout /1.263V) -1).

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  S:electronicsuite.com