Electronic Doorbell Circuit using a 555 timer and a CD4017 decade counter

This electronic doorbell circuit gives us all the possibility to change the tone of each of the 10 musical notes that the circuit can have. This means we can create our own sound sequence.

Flashing Lights for Pedestrians made 4011B IC.

This is a simple circuit that uses high-intensity white LEDs that turn on and off continuously. It may be placed in any part of the body such as an arm.

How to make a car temperature alarm?
This car temperature alarm check the car engine temperature and warns us, by means of a sound signal, when the temperature exceeds a seted value

Two Transistor Logic Probe

This Two Transistor Logic Probe is a very simple circuit that can be implemented using two NPN bipolar transistors (T1, T2) in a Darlington configuration.

Doorbell for Deaf People.

When a deaf person is alone in a house, it would be very difficult to realize that someone is knocking on the door without any visual warning signal.

The main component for the Doorbell for the deaf circuit is the CMOS 4001 integrated circuit, which has four two input NOR gates

12 volt Power Supply using 7805

This 12 volt power supply circuit is simple and useful. Sometimes we need to get 12 VDC, but we only have 5 or 9 volts regulators (7805, 7809).

This Electric Current Flow Indicator gives a visual indication that there is a current flow. Possible applications for this small circuit may be: a battery charger, a voltage power source, etc.

In order to achieve our objective we place 3 rectifier diodes in series, which in turn are in series with the load / battery.

DC motor speed controller circuit using 555

This simple DC motor speed controller circuit, works with 12 volts and controls a DC motor using the 555 integrated circuit.

Dual polarity variable voltage source

This voltage source allows for two independent voltage outputs. One positive and one negative with a maximum amplitude of +/- 15 volts, an a current up to 1.5 amps.

Variable Dummy Load for Power Supply Testing.

How to test a voltage source to know if it is good or not?. What is the percentage regulation?.

4-channel audio mixer using LM3900 IC

4 operational amplifiers, some resistors and capacitors to implement an audio mixer with a very simple design.

12 to 5 volt converter circuit (for cars)

This 12 to 5 volt converter circuit for cars is very useful. It can be used to connect 5-volt electronic devices in a car with a 12v battery. (Automotive lead-acid batteries may have a voltage of up to 13.5 volts).