Electronics > Beginners
Diode voltage clamping
NEoX:
Hi!
I want to step down voltage from sensor signal (9v) to 3.3v for MCU and generaring smallest amount of heat as possible
because next to circuit is temperarure sensor that need to be acurate . I was searching for best solution to doo that but got more confused than before.
-basic voltage divider? -waste of energy and heating up
-zener voltage shifting? -im looking for more protection way (zener shifting is just Vin-Vbreakdown..if there is more than 9v on sensor input thing wil blow up)
-op amp as comparator? -overkill?/dumb?
-simple transisotr (base 9v, collector to emiter 3.3v and to mcu?)-better way and cheaper than this?
..and at the end circuit below.. but the problem? I DON'T UNDERSTAND how it works? where that extra voltage goes..how to calculate resistors? Is this the best option? :-// :-DMM
edit: sensor is digital logic(0v or 9v)
madires:
Is the sensor's signal an analogue signal which will fed into an ADC or is it a digital signal?
NEoX:
Sensor is digital..But I'm just searching for best oprion to convert signal from 9v to 3.3v
madires:
The magic term is "level shifter". There are a lot of different types of level shifters, and it's hard to tell which might be a good solution without knowing more about your circuit.
spec:
+ NEoX
The attached simple schematic will convert 0V and 9V logic levels to input logic levels suitable for a MOS MCU running with a 3.3V supply.
I have assumed that the MCU is an ATmega 328 with the input pull-ups disabled, and that the 9V logic level input is not fast.
With a 9V input logic level the current through R1 and R2 is 10uA and with a 0V logic level input the current through R1 and R2 is 0uA, so the interface will generate very little heat.
This simple logic level converter will also give good protection from input voltage more negative than 0V and more positive than 9V. You could quite safely apply -9V and 18V without damaging the MCU input (the MCU has built in catching diodes at the Gnd pin and VCC pin).
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