24v/CMOS/24v how???I

[svtiss]

Hi
In my project there is a 24VDC device and many relays . I trying to find out how to connect 24v out to 15 CMOS inputs and back to 24v(I coil 60mA) relays .
please see the picture .
Thanks

 

[Nigel Goodwin]

Hi
In my project there is a 24VDC device and many relays . I trying to find out how to connect 24v out to 15 CMOS inputs and back to 24v(I coil 60mA) relays .
please see the picture .
Thanks

On inputs a simple resistor and clamping diode is all that's required. On outputs you use a transistor (or FET) to drive the relay - with the relay in the high voltage side of the transistor/FET.

 

[svtiss]

Thanks for the answer. I need to explain more things . I have 5 inputs and 16 outputs . I am not sure what values for resistor and what diodes to use . Could IC`s (buffers???) make it more safe for CMOS? Also I do not want to use transistors , they take to much space . Would be IC`s (drivers????) be better????
Thanks

 

[Nigel Goodwin]

Thanks for the answer. I need to explain more things . I have 5 inputs and 16 outputs . I am not sure what values for resistor and what diodes to use . Could IC`s (buffers???) make it more safe for CMOS? Also I do not want to use transistors , they take to much space . Would be IC`s (drivers????) be better????
Thanks

For resistors 22K would be fine, it's not at all critical - just to limit the current. For the diodes, any small silicon ones will do, 1N4148 would be fine, anode to the input pin, and cathode to the chip supply voltage.

If you want to use an IC package instead of transistors, there are various ULNxxxx chips available, the ULN2003 has seven drivers, and the ULN2801/3 has eight.

 

[svtiss]

do you mean cathode to +15vdc , right ???

 

[Nigel Goodwin]

do you mean cathode to +15vdc , right ???

If that's the supply to the CMOS chip, yes!.