IC for 12V operation

[mahinda jayasinghe]

I want to find a IC (AND gate function) opearting on 12V Dc (for cars)
which should be suitable to drive a small a buzzer to operate as a alarm warning to driver.
Could any one give me the idea to find the suitable IC ( 12V) for this purpose.

 

[Pyroandrew]

The 4000 series logic is your best bet. Typical supply is 3V to 15V. The 4081 is your bog standard quad 2 input AND gate chip. The 4082 is a dual 4 input AND.

Do be careful though, the voltage accross car batteries varies from 11ish volts up to almost 15V. This is within the rated supply of the 4000 series logic but sometimes the alternators get a bit funky. If this does happen, it will fry your circuit. You will need to build in some form of protection, a regulator for instance, but if you put a regulator in you may as well put a 5V one in and use 74 series logic. Also, modern cars are switching to a 48V battery system. This poses a serious problem for projects, as there are no commonly available ways of stepping down from this voltage, regulators or only rated to 37V or there abouts. There is likely to be a 12V system in there somewhere though.

 

[Pommie]

As Andrew says, car electrical systems are very noisy, so why not use a relay instead of a fragile IC.

The following should do what you want.

Mike.

 

[mahinda jayasinghe]

Thanks for your idea. I can use the relay. Can I get the NAND function and NOT function in the same way.
I want to invert the logic some time. Can I get the similar function with diode and a relay.

 

[Pommie]

For the NAND function, swap the buzzer to the other relay contact.

For the NOT funtion, swap the connection as above and just use 1 diode and 1 input. Infact don't use any diodes and just use the bottom of the coil as the input.

Mike.

 

[mahinda jayasinghe]

This is what I want. Is it possible to represent this logic with diodes and relays for 12V car.

 

[williB]

i would like to see your .doc files but every time i D/L them they come up blank. :lol:

 

[Pommie]

I can see the diagram ok. I've attached it for anyone that can't and labeled it.

The function required is

Out = /(a and /b)

This will only give logic 0 if A=1 and B=0.

This can be done with diodes and relays as shown below.

Mike.

 

[mahinda jayasinghe]

excelent idea. Thanks