DIY digital thermometer circuit

This diy digital thermometer circuit can measure temperatures up to 150°C with an accuracy of ±1°C. The temperature is read on a 1V full scale-deflection (FSD) moving-coil voltmeter or digital voltmeter.
How the digital thermometer works

Operational amplifier IC 741 (IC3) provides a constant flow of current through the base-emitter junction of npn transistor BC108 (T1). The voltage across the base-emitter junction of the transistor is proportional to its temperature. The transistor used this way makes a low-cost sensor. You can use silicon diode instead of transistor.

The small variation in voltage across the base-emitter junction is amplified by second operational amplifier (IC4), before the temperature is displayed on the meter. Preset VR1 is used to set the zero-reading on the meter and preset VR2 is used to set the range of temperature measurement.

Operational amplifiers IC3 and IC4 operate off regulated ±5V power supply, which is derived from 3-terminal positive voltage regulator IC 7805 (IC1) and negative low-dropout regulator IC 7660 (IC2). The entire circuit works off a 9V battery.

Assemble the circuit on a general-purpose PCB and enclose in a small plastic box. Calibrate the thermometer using presets VR1 and VR2. After calibration, keep the box in the vicinity of the object whose temperature is to be measured.

Automatic Fuse Circuit

To restrict / security, electric current is usually used fuse or patron is dissolved when going short will drop out and must be replaced with a new one. Then, in order not to drop out of each new change means that more money out to buy, then there fuse automatically work with the reset button. So there are problems with each short, fuse will automatic decided flow then to return it does not need to buy a new (if not broken) just press the reset the equipment will live again.

Automatic Fuse Circuit

This is one of the simplest electronic
fuse circuit one can make. The circuit uses only one transistor, one SCR, one push button switch and two resistors.

The value of R1 can be obtained from the equation; [Imax] X [R1] = 0.7V.
R2 can be obtained from the equation; R2 = [Vs] X [1K Ohms].
Wattage rating of R1 can be obtained from the equation; W = [Imax] X [Imax] X [R1].
For this circuit to work the current consumption of the load must be greater than the holding current of the SCR.

The working of the circuit is very simple. Initially the load current flows through SCR and resistor R1.The value of R1 is so selected that, the maximum load current multiplied by the resistance of R1 is equal to 0.7 volts. When the load current exceeds the maximum value the voltage drop across R1 becomes more than 0.7V and switches transistor Q1 ON. Now the transistor completely bye passes the load current and the current through triac falls below the holding current. This makes the triac OFF. When SCR is OFF there will not be any current flow through R1 and so the voltage across it falls to 0.This makes the transistor OFF, completely isolating the load circuit.The fuse can be resetted by pressing S1.When S1 is pressed the SCR is again triggered and remains latched to conduct the load current.

Auto Switch Water Pump

In this post I will show you a simple electronic circuit that can hopefully be useful in our daily lives. AUTO SWITCH WATER PUMP Often the water in the reservoir at the house we always spill when the shelter is full.


List of components:
R1 = 100K C1, 2 = 47N 5K6 R2 = C3 = 220mf/25v R3 = 680 TR1, 2,4,7,8 = FCS9012 TR3 R4 = 10, 5.6 = FCS9013 R5 = 1K-5 D1 = IN4002 R6 = 270 transformer 12v 350mA Ab = R7 = 47K Volt Cd = R8 = 47K Pump R9 = 100K Relay = 12v DC ABC = sensor (of iron, or other steinless) C1, 2 = 47N C3 = 220mf/25v Tr1, 2,4,7,8 = FCS9012 TR3, 5,6 = FCS9013 D1-5 = IN4002 Transformer 12v 350mA ab = (220v AC input) cd = Water Pumps

How it works:
Suppose we want the water level in the tank is not higher than point A and point B is lower than the water pump will live alone and when touching point A pump will die. A = the upper limit of the desired water level B = the lower limit of water needed C = is the wire / cable should always touch the paste into the body of water in the tank

C828 Tone Control with PreAmp Mic Circuit

This is tone control mono circuit with pre amp mic schematic diagram :

C828 Tone Control with PreAmp Mic Circuit
Component List :
Resistor : R1,R2 =5K6 R3,R5,R11,R19=10K R4,R14=330K R6,R7,R8,R9=50K R10=2K2 R12,R13=1K R15=15K R16=4K7 R17=33K R18=86K R20=100K
Capacitor : C1=100uF/35V C2=47uF/35V C3,C4,C5,C6=1uF/50V C7=100n C8=22n C9=2n2
Transistor : Q1,Q2 = C828
Power Supply : + - 12V DC

Working and Tested For Power Amplifier TDA2003 , and it is cheap to buy component and very simple.
See image below :
Tone Control Schematic
Tone Control with Pre Amp Mic  Component Assembly
Tone Control Circuit
Tone Control PCB

TDA2003 Power Amplifier
TDA2003 Audio Power Amplifier
Very Cheap and Simple Power Audio Speaker Active
Speaker Active with Tone Control C828 include Pre Amp Mic , using 2Amp Transformer , 6inch Woofer Speaker

Simple Tone Control Powerfull Bass

This is a circuit schematic Audio Tone Control , this Tone Control very compatible with Amplifier using TDA 2003. Below the schematic of Tone Control :

Simple Tone Control but Powerfull Bass

If you can't see the component's you can click to view larger or you can tell me about it. Transistor using C828.Which Potentio from left Bass then Treebel and last right Volume. Voltage for this Tone Control need about 12VDC - 25VDC.

And below im finished make the Tone Control

Tone Control C828

Circuit TOne Control Bass

Circuit TOne Control

Schematic TOne COntrol C828

C828 tone control schematic

Mini UPS Circuit

Here the simple Mini UPS circuit diagram. This circuit can provide an uninterrupted power supply (UPS) to operate 12V, 9V and 5V DC-powered instruments at up to 1A current. The backup battery will take up the load with no spikes or delay when the mains electrical power gets interrupted. It could possibly also be utilized as a workbench power supply that delivers 12V, 9V and 5V operating voltages. The circuit instantly disconnects the load when the battery voltage decreases to 10.5V to avoid deep discharge of your battery. LED1 indication is presented to indicate the complete charge voltage level of the battery. 

Miniature white LEDs (LED2 and LED3) are utilized as emergency lamps especially during electrical power failure at night time. A common step-down transformer delivers 12V of AC, that is rectified by diodes D1 and D2. Capacitor C1 features ripple-free DC to charge the battery and to the remaining circuit. When the mains electrical power is on, diode D3 gets forward biased to charge the battery. Resistor R1 limits the charging current. Potentiometer VR1 (10k) with transistor T1 acts as being the voltage comparator to indicate the voltage level. VR1 is so adjusted that LED1 is in the ‘off’ mode. when the battery is completely charged, LED1 glows indicating a maximum voltage level of 12V.

source : Mini UPS

IC LM35 Temperature Sensor Characteristics

LM 35 temperature sensor IC is a IC chip production Natioanal Semiconductor which serves to determine the temperature of an object or space in the form of electric scale, or can also be defined as an electronic component that is used to change the temperature changes are accepted in the electrical wholesale changes. LM35 temperature sensor IC temperature change can change a change in voltage at the output. LM35 temperature sensor IC requires +5 volts DC source voltage and DC current consumption of 60 mA in operation. Physical form LM 35 temperature sensor is an IC chip with packaging that varies, in general packaging LM35 temperature sensor is packaged TO-92 as shown in the figure below.

From the picture above it can be seen that the temperature sensor IC LM35 basically have 3 pin that serves as a source of supply voltage of +5 volts DC, as a result of sensing the output pin in the form of a change in the DC voltage and Vout pin to Ground.

IC LM35 temperature sensor characteristics are:

  • Temperature sensitivity, with linear scaling factor between voltage and temperature 10 mVolt / º C, so it can be calibrated directly in centigrade.
  • Have the accuracy or the accuracy of the calibration is 0.5 º C at 25 º C.
  • Has a maximum operating temperature range between -55 º C to +150 º C. Working at a voltage of 4 to 30 volts.
  • Has current low at less than 60 mA.
  • Have a low self-heating (low-heating) of less than 0.1 º C in still air.
  • Has a low output impedance is 0.1 W for 1 mA load.
  • have Nonlinearities only about ± ¼ º C.

70 Watt OCL Amplifier Circuit

Amplifier OCL Circuit

OCL power amplifier circuit used in the circuit above is the type of power amplifier OCL (Output Capacitor Less) with a power output of 70 Watt. Circuit 70 Watt power amplifier OCL is working on a class AB with symmetrical voltage source of VCC ± 25 volts DC to ± 32 volts DC. OCL power amplifier circuit uses a 70 watt power transistor complementary transistor TIP in 2955 and TIP 3055. 70 watt power amplifier in the circuit can be used to drive the load (4-16 Ohm loudspeaker). Power supply circuit power amplifier can use power supply circuit with current 5A symmetrical. For stereo audio system needs to make a power amplifier OCL circuit tone control + over 2 units.

Light Flasher (Blinking Lights)

This is a very basic circuit for flashing one or more LEDS and also to alternately flash one or more LEDs.
It uses a 555 timer setup as an astable multivibrator with a variable frequency.
With the preset at its max. the flashing rate of the LED is about 1/2 a second. It can be increased by increasing the value of the capacitor from 10uF to a higher value. For example if it is increased to 22uF the flashing rate becomes 1 second.

Led FLasher

There is also provision to convert it into an alternating flasher. You just have to connect a LED and a 330ohm as shown in Fig.2 to the points X and Y of Fig.1. Then both the LEDs flash alternately.

Since the 555 can supply or sink in upto 200mA of current, you can connect upto about 18 LEDS in parallel both for the flasher and alternating flasher (that makes a total of 36 LEDs for alternating flasher).

Increase Regulator Voltage Output

It is often necessary to arrange an voltage regulator IC to give a higher output voltage than that set by the regulator alone. One method to achieve this is by connecting the “common” terminal to the mid-point of a potential divider but the problem with this method is that IC regulators have a small quiescent current (~10mA) flowing out of the common terminal to ground.

The magnitude of this quiescent current is not closely controlled and hence the total output voltage becomes somewhat unpredictable. Low divider resistor values help, but there are likely to be complications of heat dissipation and inefficiency.

Increase Regulator Voltage Output

24V from 12V regulator circuit diagram

The circuit presented here avoids the problem by using the transistor T1 to generate a low impedance at the regulator common terminal by emitter-follow action, while transferring the voltage divider from a relatively high-resistance divider network. The value of R3 is not critical but must be low enough to accept the highest quiescent current without causing T1 to turn-off.

3V electronic stun gun circuit

This circuit above is a cheap version stun gun circuit that is powered by two AA baterry. The output of this electronic project is about 350V dc. The heart of the circuit is the oscillator that is composed of Windings and transistor.

3V electronic stun gun circuit
3V electronic stun gun circuit
Part List:
  1. Transistor - Tip41 or similar
  2. Resistor - 100-ohms 1W
  3. Capacitor-100nF
  4. C-1.2uF 1000V or any cap with 1000V rating
  5. D-1N4007 diode or similar

3V electronic stun gun circuit
Primary and Feedback winding

3V electronic stun gun circuit
TIP41 pins

Primary winding P is composed of 16 turns of #24 AWG wire, feedback F is composed of 8 turns of #24 AWG wire, and secondary winding S is composed of 270 turns of #30 AWG magnetic wire. P1 is connected to the collector of transistor, F2 to the 100-ohms resistor at transistor base. F1 and P2 to the battery. The output of Sec winding is rectified by Diode Bridge. The output capacitor is an electrolytic type that is rated 400V above. Capacitance of the output capacitor depends on what available on hand, but always keep in mind that the higher the value the better. this simple electronic project is dangerous when accidentally touched, thus avoid holding the output and discharge the capacitor before and after using.
One of the uses of this circuit is the camera flasher circuit.