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Various simple electronics projects for beginners

Various simple electronics projects circuits diagrams for hobbyist and beginners . Simple circuits, mini projects with diagrams and description from many electronics categories.

UTC1618 alarm circuit

A very simple low cost alarm electronic alarm circuit project can be designed using the UTC1618 CMOS IC manufactured by Unisonic Technologies .
The UTC1618 CMOS IC require few additional components and and can be used for small alarm applications.

This circuit has 6 prioritized keys for selecting 6 different sounds. S1 to S6 are the sound selection keys which are connect with internal pull-down resistors.

The sound output wiil be enabled when a key is connected to VDD. On other hands, the sound output will be disabled if a key is N.C. or connected to GND.If two or more keys are selected in the same time, the sound will be generated in cycling sequence according to the priority of the keys: S1>S2>S6>S4>S5>S3.

This sound alarm circuit require to be powered from a DC power supply between 2.5 and 5 volts and has a low cost current consumption even in active mode ( 10uA typ for stand-by an 300uA typ for active mode) .
utc1618 siren sound alarm schematic circuit

LM3911 temperature controller circuit

An very low cost simple and efficiency temperature controller electronic project circuit can be designed using the LM3911 highly accurate temperature measurement and control system designed in a single monolithic chip .
The output voltage of the LM3911 is directly proportional to temperature in degrees Kelvin at 10 mV/degree K.

As you can see in this circuit diagram , LM3911 temperature sensor chip require few additional components .
The resistor network consists of R1,R2,and R3 is used to provide the set point voltage reference for the feedback input of the LM3911.

R4 resistor is used to limit the current through the internal voltage reference of the LM3911. R5 resistor pulls the output of the IC high when the temperature is bellow the set point . The internal resistor is in series with a diode that allows a switching voltage up to 35 volts to be used.

By modifying the R2 variable potentiometer you will modify the set point of the temperature controller.
This simple temperature controller circuit needs to be powered from a 12 volts DC power supply .
lm3911 temperature controller schematic circuit

LED light circuit using NSI45090JDT4G

Using the NSI45090JDT4G adjustable constant current regulator (CCR) designed by ON Semiconductor you can design an very simple LED torch using extreme few external components .

NSI45090JDT4G device is designed to provide a cost effective solution for regulating current in LEDs. The CCR is based on patent-pending Self-Biased Transistor (SBT) technology and regulates current over a wide voltage range. It is designed with a negative temperature coefficient to protect LEDs from thermal runaway at extreme voltages and currents.

The Radj pin allows Ireg(SS) to be adjusted to higher currents by attaching a resistor between Radj (Pin 3) and the Cathode (Pin 4). The Radj pin can also be left open (No Connect) if no adjustment is required.

The maximum current that can be adjusted using this chip is around 160 mA , and the maximum input voltage is around 45 volts .
The D1 from the circuit shown here is used for reverse battery protection .
Bellow you can see how simple is to design a circuit using this chip ( all data shown bellow are for this schematic ) .
LED’s = ((Vin − QX VF − D1 VF)/LED VF)
Example: Vin = 12 Vdc, QX VF = 3.5 Vdc, D1VF = 0.7 V
LED VF = 2.2 Vdc @ 30 mA
(12 Vdc − 4.2 Vdc)/2.2 Vdc = 3 LEDs in series.
NSI45090JDT4G LED flasher schematic circuit

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