Schematics LM358 Op Amp

In this schematic, a piezo is the sensor. Piezos generate voltage when physically bent or deformed, the the foltage is in the millivolt range. The direction that the piezo is deformed determines the polarity: bend it one way, get a positive voltage. Bend it the other way, get a negative voltage.

In this circuit, the piezo is put through a full-wave rectifier bridge (the four diodes) to make its voltage always positive. The output of the bridge is sent into one of the LM358's amplifiers that's configured as a voltage summing amp. The output of that amp is then fed into the other amp on the LM358 that's configured as a DC voltage gain amp. The output from the second amp is approximately 0.2 - 3.0 V DC.

LM317T Variable Voltage Regulator

The LM317T is a adjustable 3 terminal positive voltage regulator capable of supplying in excess of 1.5 amps over an output range of 1.25 to 37 volts. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof.

Output voltage is set by two resistors R1 and R2 connected as shown below. The voltage across R1 is a constant 1.25 volts and the adjustment terminal current is less than 100uA. The output voltage can be closely approximated from Vout=1.25 * (1+(R2/R1)) which ignores the adjustment terminal current but will be close if the current through R1 and R2 is many times greater. A minimum load of about 10mA is required, so the value for R1 can be selected to drop 1.25 volts at 10mA or 120 ohms. Something less than 120 ohms can be used to insure the minimum current is greater than 10mA. The example below shows a LM317 used as 13.6 volt regulator. The 988 ohm resistor for R2 can be obtained with a standard 910 and 75 ohm in series.

When power is shut off to the regulator the output voltage should fall faster than the input. In case it doesn't, a diode can be connected across the input/output terminals to protect the regulator from possible reverse voltages. A 1uF tantalum or 25uF electrolytic capacitor across the output improves transient response and a small 0.1uF tantalum capacitor is recommended across the input if the regulator is located an appreciable distance from the power supply filter. The power transformer should be large enough so that the regulator input voltage remains 3 volts above the output at full load, or 16.6 volts for a 13.6 volt output.

Solenoid and Sensor Control 4N35

To control the solenoid motors, we elected to use optoisolators. The control pins of the MCU were attached to the optoisolators which turns on and off the solenoid by controlling a TIP31 transistor. The TIP31 serves as an on/off switch for the solenoid. The optoisolators (4N35) were needed so that the MCU was completely isolated from the circuit. This protected the MCU because there were no physical connection between the MCU and the power supply. The 4N35 works by using a phototransistor that senses LEDS when the device is turned on.

The sensors were measured by a voltage division circuit coupled with an operational amplifier to achieve the desired results. The voltage outputted from the sensors was sent to the ADC of the MCU. The reference voltage of the MCU ADC was set to 5.0 volts which would correspond to the digital value 255 since only the top 8 bits of the ADC were used. We simply used this digital value to determine exactly how much juice we have dispensed.

DC Voltage Doubler - 74HC132

74HC132
This is a cheap DC Voltage Doubler Circuit diagram, which requires a few components and will deliver 10V from a 5V power supply. If the oscillator must be built from a non-functional gate then is required 2 more components: R1 and C3.
The most important parameters of this voltage doubler circuit are given in the table below. Note that because of the IC tolerances these data may have some differences.

SPS250A power supply 2SC2625

A SMPS I take on trips I forgot is NOT auto voltage sensing on input and was still set to 110V after recent US trip.

Pretty obviously the power transistors got fried and rather than junk it I thought I should fix it

This is dealing with mains voltage so do not do this unless you know what you are doing as the voltages are lethal.

It took a bit of digging to find the circuit diagram (thought it was on the pdf that came with it), still haven't found it exactly but this is very similar except mine appears to run the fan full all the time instead of having a fan control board on the lower right here.


These power supplies are widely in use and all are called SPS250A in the name and are all made in China under various names... so if yours has SPS250A in the name and looks like mine then chances are it is the same but no responsibility if it is not, use information at own peril (and this is running at mains voltage which can kill so do not do this without a healthy respect for high voltages).

The two NPN power transistors 2SC2625 were removed still attached to their heatsink.


Note all the common mode filtering on the input side (top right corner).
Mine has had the right hand transistor crater and the other is short circuit between the pins.

Anyway suffice to say power supply can be easily repaired.

I hear that it might make sense to replace the 2Sc2625 10A versions with 2Sc3220 which are 15A versions but I would source them in HQEW.net  .

Multi Output DC to DC Converter LM2596

This is the circuit diagram of DC to DC converter based LM2596, the circuit has a single input supply and multiple voltage outputs. The circuit has an input voltage range of 15V to 40V. It has 5 outputs: 3.3V at 1.5A; +12V and −12V at 50 mA each; and +5V and −5V at 50 mA each. The 3.3V, +5V and −5V outputs are regulated with ±5% accuracy over line and load variations.

Circuit parts list:

    Cin : 220 μF, 50V, Nichicon UPL1H221MPH
    C1: 270 μF, 63V, Nichicon UPL1J271MRH
    C2, C3: 47 μF, 35V, Nichicon UPL1V470MPH
    D1: MBR360,
    D2, D3: 1N459,
    C4, C5: 0.01 μF
    IC1: LM2596-3.3 (SIMPLE SWITCHER® Step-Down Voltage Regulator)
    IC2, IC3: LM78L05, and LM79L05. (3- Terminal Regulators)
    L1: Custom Inductor with three windings (W1, W2 and W3) with the following specs:

        W1: 47 μH; Peak Current: 2.6A, RMS Current ≈ 2.32A
        W2: Number of turns = 3.4 x Number of turns in W1; RMS Current; 113 mA
        W3: Same as W2

The +12V and −12V outputs are regulated with ±20% accuracy. A typical application of this circuit is where the 3.3V output provides the power to the main circuit which is 3.3V logic, the ±5V outputs power the 5V logic and ±12V outputs provide the bias supply of op-amps.

The efficiency of the circuit with full load at all outputs is 75%. The ripple voltage across the 3.3V output is less than 20 mV and that across the ±12V outputs is less than 30 mV. The ripple across the ±5V is less than 10 mV.

Interesting mosfet voltage regulator IRF3205

  The mosfet used was the IRF3205 Enhancement Mosfet. Its function is to boost the current induced into the transmitting coil to increase its distance level. Mosfet ratings; Peak Drain to Source Voltage (VDS)= 55V On Resistance = 8.0 ohm Peak current = 110A when VDS = 10V So the current used was derived using the equation; ION = k (VDS(on) – VDS(th))2 Using the ratings to get the constant k we have, K = 110A/ (10V – 4V)2 K= 110/62 K = 110/36 K = 3.10AV2 Having gotten the constant k as 3.10AV2, we can derive our drain current as; I = 3.10 x (9V – 4V)2 I = 3.10 x 25 I = 77.50A

  The inductance of the inductor to use is derived using the equation; L = n2 x R2/ 9R + 10x Where, L is the inductance N is the number of turns R is the radius of coil X is the distance of turns To get the required reactance of the coil to use, we divide the DC supply Voltage by the Drain Current of the MOSFET. Therefore, XL = 21.21/77.50 XL = 0.27ohm If Reactance of an inductor XL = 2 x 3.142 x f x L, then 0.27 = 6.284 x 50 x L L = 0.27 / 314.2 L = 0.0008593H RECEIVING CIRCUIT: The receiving circuit has basically the receiving coil, half wave rectifier circuit/filter and the voltage capacitor. The value of R is used to set the charging current to a fixed value which is determined by the Charging voltage/ charging current. For this project, the charging voltage was 5V DC. And the charging current required was 500mA. Therefore the value of R will be; R = 5/0.5 = 10ohm

TEA2025B bassed amplifier circuit and explanation

A very simple audio amplifier electronic project that can be used in small portable audio applications can be designed using the TEA2025B audio amplifier IC . This audio power amplifier project supports a wide input voltage range between 3 and 15 volts .
Input capacitor is PNP type allowing source to be referenced to ground.
In this way no input coupling capacitor is required. However, a series capacitor (0.22uF)to the input side can be useful in case of noise due to variable resistor contact.
The bootstrap connection allows to increase the output swing. The suggested value for the bootstrap capacitors (100μF) avoids a reduction of the output signal also at low frequencies and low supply voltages.
The voltage gain is determined by on-chip resistors R1 and R2 together with the external RfC1 series connected between pin 6 (11) and ground. The frequency response is given approximated Input capacitor is PNP type allowing source to be referenced to ground.
The frequency response is given approximated : VOUT/VIN= R1/(Rf +R2 +(1/JWC1))
The maximum output power that can be obtained using the TEA2025B audio amplifier in stereo mode is around 2.3 watts on a 4 ohms load .

Best DC power supply 3Amp LM317T

There is the high quality power supply to provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous 1.25V to 20V. Using LM317T and 2N3055 are main parts so easy to made and cheap.

Friends would known the power supply as well. Because you must use in various circuit experiment. It originally had a small supply current, when found projects that uses lot of current. Such as an audio amplifier circuit so provide current is not enough.
This project can help you. Because of provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous. And you do not have to worry. This creates a simple and economical. If interested, please read on.

How it works
In the circuit below can be seen that, when opening switch S1 is current through the transformer. To convert from 220V AC to 18V, then through diode bridge rectifier BD1. But is a DC supply that still not smooth. Then, a filter capacitor C1 serves electricity, out of BD1 to be more smooth with the LED1 to show that power is supplied to already.
When the filter current is smooth on one order. The current will through the regulator circuit that the main components are IC1(LM317T) and Q1(2N3055).
-IC1 is the regulator IC number : LM317T.
-Q1 is power transistor NPN type number : 2N3055.

Before the DC volt through IC1 would have C2 served filter noise off. When we adjust the variable resistor VR1 or rotary switches S3 twist choose it. Will cause changes the voltage at the ADJ pin and OUT pin of IC1. Which will be resulting the voltage drop across the base pin and the emitter pin of transistor Q1 changes. Makes the voltage on the connector is changed accordingly. And before the voltage is applied to current C3 filter to smooth again.
Detail see in circuit image.

Voltage Comparator Circuit with MOSFET - CA3140

I would like to present the voltage comparator circuit ,you can bring this circuit to apply with your project that concern in voltage checking or comparison.
This circuit provides an indication if has the input voltage differs from the two defined limits, V1 and V2 voltage source. We can adjustable limit and made to trigger from the adjustable “window”.

As to the amplifiers to the CA3140 MOSFET is used in circuit. They are used to benefit, as they have very little influence and can counteract the tension for change near 0 volts.

If a second operational amplifier is used as LF351 and CA741, will require a zero transverse force control.

This is only a predetermined 10k contact between pins 1 and 5, the wiper connected to the negative supply voltage and the pin of the fourth operational amplifier With this circuit, both operational amplifier, the LED when the input voltage out of range, 1N4148 diodes both “Y” to the exit door. The input voltage to be monitored is supplied through a 10K series resistor to the inputs of the two amplifiers operational amplifiers. If the input voltage exceeds the threshold value V1 and CA3140, the output voltage swing almost completely and turn off the LED. Similarly, if the input voltage is lower than the limit defined by V 2, then this is the operational amplifier moves to the Vcc and light the LED.