This simple timer can keep a 12 V lamp on at intervals between a few seconds to a few minutes depending on the value of the capacitor used and the setting of P1. Lamps with currents up to 1 A can be used, depending on the MOSFET used.
We can use this circuit as a timer for games, gymnastics, process control, etc. The power supply is made by source with capacity according to the lamp used. In Figure 1, we have the complete diagram of the timer.
The assembly using a terminal strip is shown in Figure 2. The MOSFET transistor must be provided with a small heat radiator.
To use, simply press S1 for a moment. The lamp will light up and remain so for the time interval set at P1.
Material list
Q1 - IRF720 - Power MOSFET - any type
R1- 10 k ohms x 1/8 W - resistor - brown, black, orange
R2 - 4.7 M ohms x 1/8 - resistor - yellow, violet, green
P1 - 1 M ohms at 4.7 M ohms - trimpot or potentiometer
C1 - 100 to 1000 uF x 16 or more - electrolytic capacitor
X1 - 12 V up to 1 A - incandescent lamp
S1 - Pressure switch NA
Miscellaneous: terminal strip, radiator for Q1, socket for lamp, wires, solder, etc.
