Using this schematic circuit we can make a very simple SIM card reader . The SIM card reader circuit is based on the MAX232 circuit and require few external components . This SIM card reader circuit require a 5 V external power supply . This SIM card reader needs a PC software to work .
All capacitors are 10uF polarized and the R1, R2 resistors value is 220 ohms . The D1 is a red LED and D2 is a green LED .
This circuit is a very simple light detector circuit which use few external components . The light detector circuit is based on a 741 operational amplifier and a LDR (Light Dependent Resistors) which is used to sense the light intensity .
Using this electronic schematic circuit we can monitor the voltage of some power supplies or the voltage of other circuits .
This circuit is very simple an required few components . The monitored voltage for this undervoltage and overvoltage monitor circuit is maked using two Zenner diodes . If the value of the monitored voltage goes below or above the value of the zenner diodes the LED will light .