microcontroller configuration help.

[yyyyaser]

thanks in advance,

i need help for this circuit shown

- the wireless receiver only produces pulses (12v for on , -12v for off), so a regular relay cant be used because once the pulse is gone , it wont conduct , and i cant find an impulse relay.

- i want to use a microcontroller, but is there a micro that can take -12v as a logic zero and +12v as a logic one.

-if i cant get one of these, how can i configure the circuit to be used with a regular microcontroller.

-can i use a voltage regulator this way:i/p:12v , o/p:5v.

 

[3v0]

Use a MAX232 or similar chip to translate. They are designed for just that purpose.

 

[yyyyaser]

thanks , but where can i find the exact one that i want (-12,+12) --> (0 ,5)

this one converts from (3,15)

 

[3lectrokid]

have a look **broken link removed**

it requires four 0.1uf capacitors and it works by if there is +12v in an input it will output 0v which you can use in most 5v micro controllers. if it has -12v in the input it will output 5v. Are you sure +12v equates to a logic one because in the RS232 specification it is the other way around where a positive voltage is logic 0. That's how the MAX232 works.

If not you will need to build an inverter or invert the signals in code

Dave

 

[3v0]

thanks , but where can i find the exact one that i want (-12,+12) --> (0 ,5)

The MAX232 is designed to translate between TTL levels and RS232 levels which is what you need.

 

[yyyyaser]

thanks any way

 

[colin55]

You need something like this:

 

[3v0]

thanks any way

What is with the "any way".

People have been using this chip to do exactly what you want to do for about 20 years. Why do you think you need something different ?

this one converts from (3,15)

The MAX232 will accept voltage levels lower then +12 and -12 but be assured it will process +-12 just fine !

 

[yyyyaser]

input : +12v --> output:5v

input : -12v --> output: 0v

if this is how this chip function , then thank you very much (not any way) .

but what i understood from the wikipedia document is that what it does is:

input : +15v --> output:5v

input : +3v --> output: 0v

 

[yyyyaser]

You need something like this:
View attachment 47338

thanks , i wanted to use the microcontroller.
but i might use that as well.

 

[blueroomelectronics]

What is this device for?

 

[yyyyaser]

i m using the wireless device of the car to control the operation of an electric motor.
thats why it produces 12v (car battery voltage).

 

[yyyyaser]

i m thinking about something else , and i want to take your opinion

what if i use an analog to digital converter.

i think at least one bit from the output will be different in the two cases(+12,-12)

and i may use this bit -which will be 0 or 5 - as a microcontroller input.

is that applicable?

 

[blueroomelectronics]

Where are you getting -12v in a car?

 

[yyyyaser]

the wireless receiver takes its vcc from the car battery and produces +12v or -12v normally to open or close the doors , but i want to use this singal to switch a motor (water pump) on and off.

 

[3v0]

input : +12v --> output:5v

input : -12v --> output: 0v

if this is how this chip function , then thank you very much (not any way) .

but what i understood from the wikipedia document is that what it does is:

input : +15v --> output:5v

input : +3v --> output: 0v

For inputs of 15V down to 3V it will output 0V
For inputs of -15V up to -3V it will output 5V

It seems this is inverted from what you want but a 7404 or a transistor can be used to invert the logic. The beauty of using the MAX232 and the inverter is that you do not have to work with transistors and the resistors required to make the work right.

If you do want to go the transistor route that is ok too.
**broken link removed**