Maker Pro
Maker Pro

Discrete interface for 24V with microcontroller

mysig

Jun 8, 2022
1
Joined
Jun 8, 2022
Messages
1
Hello,
I am just doing some prototyping for an interface with external 24V from 5v microcontroller, what would you recommend for a discrete solution?

My current idea, is with pnp and npn transistors and some pullup/pulldowns *what i have at home*. Any other smart way?upload_2022-6-8_16-9-14.png
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
12,613
Joined
Nov 17, 2011
Messages
12,613
Logic level Mosfet maybe?
A logic level MOSFET will be the most simple solution. It will, however, invert the signal from the µC, This is not a big issue as you can easily invert the signal in software so the output of the logic level MOSFET will be in the correct polarity.
upload_2022-6-8_20-27-27.png

Both circuits haev in common that the output impedance in the inactive state (low in your circuit, high in my circuit) is comparatively high: 10 kΩ defined by R1. If that is o.k. for the circuit driven by the output the go ahead with one of these circuits. Ig you need a lower impedance, R1 can be lowered to e.g. 1 kΩ. I do not recommend to lower it any more due to the increase in power dissipation when the driving transistor is on.
 
Top