Fig. 1

Interfacing Microcontrollers to CMOS and MOSFET Circuits

Fig. 1 illustrates connecting a 5-volt microcontroller to a 12-volt MOSFET switch.

Q1 and Q2 are N-channel 2N7000 MOSFETs. The CD40106B is a HEX inverter circuit using only 2 of the six available inverters.

The CD40106B +Vcc is connected to +12-volts (pin 16) and ground (pin 8) are not shown. The four unused inputs should go to ground.

The CD40106B has Schmitt trigger inputs.

A LOW output from the PICAXE is inverted to HIGH on the MOSFET gate turning on the MOSFET.

Fig. 2

Fig. 2 is the same as Fig. 1 but two of four 2-input NAND gates from a CD4093B. This acts as a Schmitt trigger inverter.

Note that Q1 and Q3 work as a non-inverting voltage interface. What if one needs an inverting input? Fig. 3 below does just that.

Fig. 3

Below is a simple program for the PICAXE-08M2 used in the video.


#picaxe 08m2 ; type chip used

symbol LED1 = C.1
symbol LED2 = C.2

LOW LED1
HIGH LED2

main:
toggle LED1
toggle LED2
pause 500
goto main