Welcome to this page. I have selected a few simple circuits to use for hobby or at home.
Nothing complicated each circuit is kept simple to understand and to build.
All circuits are in PDF format and can easely been printed. At the bottom of the page you will find the Adobe link.
If you have any questions do not hesitate to contact me, I will be glad to answer all your questions.
Mains On Warning
This little circuit using one 4093 and a few components gives at a frequency of once every 2 minutes
a series of bip's (6 to 12). Very handy to connect with appliances which need attention like battery chargers or
The moment a fuse choose to blow is allways in the evening (Murphy's Law). Most of the electrical cabinets are placed
in garages or cellars mostly inaccessible. With this little circuit you will be able to see your cabinet.
The 2 super LED's will give enough light to switch on again your fuses.
When mains is present the battery is continuously charged at approximately 7mA.
To power this circuit I used the doorbel transformer mostly installed inside the cabinet.
Ever tried to check if your remote control is still working, if Ir signal is still send ?
Here is the solution with 5 components. Any Ir signal received by the Ir finder will generate an audible signal.
The heart of the circuit is the TSL245 Ic. As soon as he picks up an Ir beam he will output an audible frequency.
The higher the frequency the stronger the signal.
Ever had problems with water in your house ? This circuit will warn you when water gets on the floor.
Put this circuit with a 9V battery in a little box, fix the printed circuit on the bottom with 4 long screws, so they protude
out of the box. As soon as these screws, connected to sensor inputs A1-B1 and C1, feel water the 10µf condenser
charges and a pieping tone comes out the piezzo speaker.
On dry surfaces there will be no current drawn from the battery.
The push button is used to test the circuit.
With 2 transistors and a few components you will make a light sensitive switch. The sensor is a common LDR
and sensitivity is adjusted by a 5k potentiometer.
Depending on the LDR used you can experiment to find the appropriate potentiometer value.
I used BC337 transistors but any equivalent will do.
This is what I call simple !!
For those of you hobbying with radiocontrolled boats cars or trucks, this circuit will allow you to switch lights or events
ON or OFF.
The circuits acts as an integrator, as soon as a train of pulses (1 to 2 ms.) in presented on the input the capacitor
charges and fires the first transistor. The relay energises and lights goes on.
When pulses are stopped relay deenergises.
This a very handy piece of testequipment. Easy to assemble and few components. This circuit will generate
a 1 to 2ms signal to simulate servomotors used in radiocontrolled boats or trucks.
The potentiometer will vary your servo from 0 to 100%.
Just point this small device at the TV and the remote gets jammed.
The 555 is wired as an astable multivibrator for a frequency of nearly 38 kHz.
It is required to adjust the 10K potentiometer while pointing the device at your TV to block the IR rays from the remote.
This can be done by trial and error until the remote no longer responds.
Many a times one needs an extra telephone ringer in an adjoining room to know if there is an incoming call.
All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires.
This circuit does not require any external power source for its operation.
Resistor R3 is used for bell sensitivity adjustment.
The bell frequency is controlled by resistor R5 and capacitor C4, and the repeat frequency is controlled by resistor R4 and capacitor C3.
A little experimentation with the various values of the resistors and capacitors may be carried out to obtain desired pleasing tone.
This is a CMOS IC (CD4033) based circuit which can be used to detect presence of mains AC voltage without any electrical contact
with the conductor carrying AC current/voltage.
If AC voltage is not present, the display would randomly show any digit (0 through 9) permanently.
If mains supply is available in the conductor, the electric field would be induced into the sensing probe.
Since IC used is CMOS type, its input impedance is extremely high and thus the induced voltage is sufficient to clock the counter IC.
Thus display count advances rapidly from 0 to 9 and then repeats itself. This is the indication for presence of mains supply.
This circuit will beep when refrigerator door is not properly closed.
Circuit to be located near the refrigerator light.
When door opens the 22µF capacitor will charge, and when the voltage reaches the zener voltage, the beeper sounds.
The darlington can be a MPS-A14 or two 2N4401 connected as shown.