5-Band Equaliser Circuit

Above circuit is a 5-Band graphic equaliser circuit from Electronic For You Magazine, published May 2007. This equaliser uses low-cost op-amps NE5532 or LM833. Those ICs are good-quality op-amps powered by a single voltage supply are readily available in the market.

This 5-Band equaliser circuit is powered by a 12V DC regulated power supply. A well-regulated power supply using 7812 is recommended.

Download 5-Band Equaliser Circuit document from Electronic For You Magazine:
» Download Link

4 Band Audio Graphic Equaliser Circuit

This is the circuit of 4 band audio graphic equaliser. The equalizer will cut and boost the four range of audio frequency, that are:

• Low frequency: Freq. 35-680Hz
• Medium frequency: Freq. 150-3kHz
• Medium/semi high frequency: Freq. 450-8.5kHz
• High audio frequency: Freq. 750-15kHz

Circuit note: Use regulated power supply, metalfilm resistor, MKM nonpolar capacitor and tantalum bipolar capacitor for best audio quality result.

This circuit is available in PDFdocument. Download 4 Band Equalizer circuitfrom the following link:
Download Link

5W / 150MHz RF Amplifier Circuit

This is a 5W -150MHz RF amplifier circuit. It applies the MRF123 TMOSFET. The MRF123 is a very high gain FET which potentially unstable at both VHF and UHF frequencies, so the 68 Ohm input loading resistor has been used to enhance the stability. This RF amplifier has a gain of 14 dB and a drain effeciency of 55%.

1W FM Booster based 2N4427

This is the circuit diagram of linear FM Booster / RF amplifier based 2N4427 Philips transistor. The RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear with BGY133 or BLY87 and so on. Its power supply has to give 500mA current at 12 Volts. More voltage can boost the distance but the transistors will be burned much earlier than usual.! In any case do not exceed the 15Volts. The Amp offers 15 dB in the area of 80Mhz to 110 Mhz. L4, L5, and L6 are 5mm diameter air coils, 8 turns, with wire 1mm wire diameter. This is an easy project, but will give you great results.

Simple LM358 Mic Preamplifier

This is a simple LM358 microphone preamplifier schematic diagram. The pre-amp circuit is very easy to build and.. it's a low cost project... The variable resistor R5 is to adjust the LM358 op-amp gain. The LM358 has dual op-amp circuit modules, you may use a single LM358 to build two channels mic preamplifier.

Parts List:
R1, R3, R4 = 10K
R2 = 1K
R5 = 100K-1M Potensiometer
C1 = 0.1uF
C2 = 4.7uF/16V
IC1 = LM358 dual op-amp single power supply
Mic = Electret Microphone

three up decision maker

PCB Layout

This electronic device will help you make important decisions (or not). While it is deciding the solution to your problem it will convince you how difficult it really is by a painful growling noise - or maybe this is normal when you have to think!

Once the push button is pressed, the circuit uses a 555 Timer in a astable (free running multivibrator) fashion.  The mathematics indicate that we should be getting a square wave signal at a frequency of around  124 Hz ( cycles per second) see 555 Worksheet.  This signal is fed into the4017 Decade Counter which counts 0 - 1 -2 - RESET.  Where RESET is an instantaneous process that sets the counter to 0.  For all purposes, the count is 0 - 1 - 2 - 0 - 1 - 2 ..............  This counting sequence is produced at pins 2, 3 and 4 of the 4017 .  We have assigned pin 2 as NO, pin 3 as MAYBE and pin 4 as YES.  The output from the 4017 is passed through 390 ohm resistors to limit the current (protect the 4017) before passing through the coloured LED's to 0V.  The push button also supplies current to the buzzer making the noise while it decides.

When the push button is released the 555 stops the signal and the 4017 displays the current count YES, NO or MAYBE.

To construct the project

1. Check the PC Board for damage or breaks in the tracks. A CdS Circuit Tester is ideal, or use a continuity tester mode on a multimeter. Repair any damaged tracks.
2. Push the IC sockets into their holes. One has 8 pins, the other 16. The pads on the board will match the legs. Note that there is a notch in one end of the sockets. On the layout sheet there is an instruction about the locating DOT of each IC. If you turn the IC sockets so the notch is where the locating dot is to go, then you will be saved a bit of thinking later when you are ready to push the ICs. into place. Push the sockets right down to the board. It is strongly recommended that you solder the sockets in place right away. See Soldering Technique . Any spreading of solder across to the fine tracks between the pads will prevent the project from working.
3. Identify the resistors by their colour bands See Resistors , and check with a multimeter. Bend the legs to match their holes and mount them to the board. Spread the legs on the other side to hold them in place. They may be soldered if convenient.
4. The polyester capacitor (greencap) can be inserted. They are not polarised so can go any way round.

5. The electrolytic capacitor is polarised.  The negative stripe on the capacitor shows the negative leg.

6. The LED's are polarised.   Insert them in the correct polarity and colour placement. The A leg is longer.
7. The Piezo transducer has Red (+ ve) and Black (-ve) leads. The board is marked for correct connections. The holes in the board at these points are larger to take the pins in the Kit. This makes termination of the wires much easier.
8. Remove the ICs from their anti-stat cases and identify them - 8 & 16 legs. You will find that the legs are spread too wide to fit easily into their sockets, so hold one set of legs sideways on a flat surface and press down to bend them inwards a little. Follow with the other side. Offer the IC to its socket and check that the legs have been bent in enough to slide into the socket. Look for the locating DOT and turn the IC to match the sheet. Push it firmly into place. Repeat the process for the other IC.

9. Offer the holder into the two holes and push home.  Note the battery holder is inserted from the track side of the PCB. Apply the soldering iron to the legs in turn until you have pushed the holder down close to the board. Next, fuse the solder to both pads and legs to form a good contact.

10. Attach the switches in their respective positions.  Insert a bettery and test the project.

Generally the unit will work right away. If it refuses then you must check locations, values, and polarity of all components against the layout sheet.
If these check out then remove the battery holder and inspect all soldered joints. Re-solder any that look suspicious, in fact you could touch each joint with a hot iron to eliminate any soldering problems.
You might check the track again to locate any fine breaks,

Contact CdS electronics

50 Watt Amplifier

This is a handy, easy to build general purpose 50 watt amp. The amp has an input for a radio, TV, stereo or other line level device. It also has a phono input for a record player, guitar, microphone or other un-amplified source. With the addition of a low pass filter at the input, it makes a great amp for a small subwoofer.

Parts

R1(1)200 Ohm 1/4 W Resistor

R2(1)200K 1/4 W Resistor

R3(1)30K 1/4 W Resistor

R5(1)1K 1/4 W Resistor

R6(1)5K 1/4 W Resistor

R7,R10(2)1 Meg (5%) 1/2 W Resistor

R8,R9(2)0.4 Ohm 5 W Resistor

R11(1)10K Pot

R12,R13(2)51K 1/4 W Resistor

R14(1)47K 1/4 W Resistor

C1(1)100uF 35V Electrolytic Capacitor

C2(1)0.011uF Capacitor

C3(1)3750pF Capacitor

C4,C6(2)1000pF Capacitor

C5,C7,C8(3)0.001uF Capacitor

C9(1)50pF Capacitor

C10(1)0.3uF Capacitor

C11,C12(2)10,000uF 50V Electrolytic Capacitor

U1,U2(2)741 Op Amp

U3(1)ICL8063 Audio Amp Transister Driver thingy

Q1(1)2N3055 NPN Power Transistor

Q2(1)2N3791 PNP Power Transistor

BR1(1)250 V 6 Amp Bridge Rectifier

T1(1)50V Center Tapped 5 Amp Transformer

S1(1)SPST 3 Amp Switch

S2(1)DPDT Switch

F1(1)2 Amp Fuse

SPKR1(1)8 Ohm 50W Speaker

MISC(1)Case, Knobs, Line Cord, Binding Posts Or Phono Plugs (For Input And Output), Heatsinks For Q1 And Q2

1. I know I skipped R4. That is not a problem :-)


2. Distortion is less than 0.1% up to 100HZ and increases to about 1% at 20kHz.


3. I haven't been able to find anyone who sells a suitable T1. You can always use two 24V 5A units in series. If you are building two amps (for stereo), then I would suggest using an old microwave transformer and rewinding it. Follow the instructions in the 12V To 120V Inverter, execpt wind 26 turns, twist a loop (center tap) and wind 26 more turns. That should work out to around 50 volts. You may need to add or remove turns depending on your transformer.


4. Q1 and Q2 will require heatsinks.


5. You may have trouble finding U3 because it is discontinued. Please don't email me about sources...I can't find it either. See if any of the sources in Where To Get Parts has it. A possible source was sent in by JBWilliams

source