hi , i have a problem in interfacing sensors which work on 9-12 Volt
and a microcontroller which work on 5 volt .
Any ideaS?

 

Probably have to use two power supplies. If your sensors have analog outputs, you're going to have to put them through an A to D converter to make use of them anyway.

 

Use an LM339 quad Comparator or an LM393 dual Comparator. They work well on a single supply. The output is a TTL/CMOS compatible open collector output which can be pulled up to whatever Vcc your processor is running on. If you look very carefully they may even have single comparators in a SOT23-5 package. Be careful you don't have both of the inputs outside the common mode range. With a reference at V+/2 this should be no problem if V+ is in the 9-12Volt range. Don't forget the bypass caps on the comparator either.

 

How about two resistors as a voltage divider? All the other solutions seem overly complex to me for such a simple problem.

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We kind of have to know more details about the sensor. What is it's output. digital or analog ? What kind of sensor, etc.

Quality of answers we be in proportion to the quality of the specfic information you can provide......

Lefty

 

it is an IR sensor which its output is 9-12 so this signal should be input to the micro controller 8051 atmel.

 

How about a link to a datasheet. Your answers are just not very helpful.

 

it is a 8051 atmel micro controller which is known
and the sensor outputs 9 volt all i need is to interface it wid the micro controller input pin

 

Well if it's a digital ouput from the sensor, that is it is either 9v or 0v then a simple voltage divider of say two 10k resistors should work. CMOS ouput to top of top resistor, common voltage of both sensor and micro to bottom of bottom resistor and micro input connected to where the two resistors hook together. That should give you a 4.5v input to your micro.....

 

You need to check the max output from the CMOS IC's.

TTL requires a larger operating current per gate then Cmos, check IC datasheets.

You may have to drive it via a Cmos buffer.

Also for TTL you have to use pull up / down resistors on gates not used, to avoid false triggering.

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