I have 2 external signals arriving to my board, A and C. B is generated inverting A. They 3 will be used for generating 3 switch control signals: A', B', C' at every point (there will be 8x3 24 switch). Every one will be 12V or 0V. 12V state means to activate the coil of a relay, because of coil needs 12V for closing contacts.
According to the application, there can only be one active switch at the same time I thought a way for ensuring that only A', B' or C' will be ON and the other two signals: OFF.
I though about muxes and logic gates that supports input and output voltages of 12V. So I found useful products. But after thinking that I was having a good solution, I realized that:
- these coils have a resistance = 150 Ohms. So Icoil = 12V/150 = 80mA -relay datasheet don't say anything about cutoff current, but drop-out voltage: 1V -
- the most of existing logic gates provide a max output current = 10mA.
- so, I'm afraid that coils will not be energized because 10mA < 80mA
- I dont' know if my explanation and situation is correctly deduced. Is it generally only needed to have 12V or may the coils need 12V + I > 80mA?
- If I can' t find AND and NOR gates with this current output features, how do you solve the situation?
- Must I say bye to modifying control signals using logic gates? or can be applied some electronics to the outputs? I don't consider using current elevators due to the quantity of them that I would need.
Any information will help.