8 inputs and gate to 1 output

taggr061362

Member
T
Join Date
Nov 2014
Location
Ohio
Posts
4
All,
I'm currently working on a project were I need to read 8 24 vdc 3 wire prox. switches and output to 1 PLC input. I'm very limited on space. Does anyone know if the make an 8 AND gate for 24VDC sensors? All the sensors need to be high before output to the PLC.
Thanks,
Tim
 
A quick search on Mousers web page turned up nothing, I only got hits for 2 and 3 input AND gate.

You would need to use 4 chips to make it work with these.
(They did have 8 input Nand though, so that seemed odd that nothing matched for a 8 input AND chip)

I did find a couple on the www but all said "obsolete part"

Not knowing the nature of your project its hard to say, but if you have room for something a little bigger (alot bigger) than a IC Chip then you could use a very small logic controller like Siemens Logo (or other brands)then write your own logic and use one of the relay output to your plc.
Maybe put logo in a separate box outside your project.

Logo is:
2.75 inches wide
3.5 inches tall
2.25 inches deep
Logo is avalible with 8 inputs & 4 relay outputs and cost around $100 + $65 for software.

BCS
 
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Could you mount small relays near the prox switches and series up the contacts before connecting into the plc?
 
{Brain ****}

Went and had lunch and thinking better now.

You could use the 8 input NAND Gate and just invert your instruction for the input in your plc.
0 = True instead of 1 = True

Google Mouser Electronics 8 input Nand.

If you can use the chip then it will only cost you a few bucks.

BCS
 
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I have 32 small grippers on an unload arm for LSR injection machine. I have 4 banks of 8 grippers with sensors on each to sense they are in the open position. They use to make a 6 AND small card with 1 output that would work very nicely. The grippers remove a dump groove to avoid defective parts. I don't think I have room for 32 relays on the arm. Thanks for the information.
 
You can generally wire prox switches in series. I haven't tried it with 8, you may run into voltage drop issues with that many, but before you go getting overly complicated about it I'd try just hooking them up in series, adding one at a time and seeing how far you can get before they stop working, if they do!
 
And if that doesn't work, see if you can swap the sensors for a reverse polarity setup. Then you'd need them all to be low, and you could wire them all in parallel. You'd need to put that into the context of your application though - what are the consequences of a sensor failing low (as they usually do) if they're all in parallel?
 
I have wired sensors in series before, I could only get to 3 before the voltage was to low to pick up on the PLC. I can try it and see how it works. Thanks,
 
There is no safety issues or no damage would occur if one of the grippers is closed during the run. It just breaks the consistence of the cycle and that is very important. The operator would have to manually remove the sprue if they notice.
 
Maybe I am not thinking more clearly after lunch after all!

I dont think you will find IC Gates that will handle 24 volt directly. So unless you are using a lower voltage then this may not work for you.

You could build your own gates using transistors though and then you could use 24vdc.

Good Luck
BCS
 
taggr061362 said:
I have wired sensors in series before, I could only get to 3 before the voltage was to low to pick up on the PLC. I can try it and see how it works. Thanks,
Click to expand...

Yes, I didn't think you'd get that far. I've only used two or three.

taggr061362 said:
There is no safety issues or no damage would occur if one of the grippers is closed during the run. It just breaks the consistence of the cycle and that is very important. The operator would have to manually remove the sprue if they notice.
Click to expand...

In that case, if you have the option to swap the sensors out for the reverse polarity, I think that would be by far the easiest option. No extra components, no extra wiring - just connect all the 24V together, all the 0V together and all the switch wires together and connect the switch wires into the PLC input. If there are no safety/damage issues then great. If a sensor fails the machine is going to stop anyway until the sensor is replaced, all that changes is the sequence of HOW the machine stops when it fails.

There are other ways, but if your primary concern is lack of space to wire anything/lack of inputs, this is probably your best bet.
 
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taggr061362 said:
I have 32 small grippers on an unload arm for LSR injection machine. I have 4 banks of 8 grippers with sensors on each to sense they are in the open position. They use to make a 6 AND small card with 1 output that would work very nicely. The grippers remove a dump groove to avoid defective parts. I don't think I have room for 32 relays on the arm. Thanks for the information.
Click to expand...

These take up very little space, they are 6mm wide.

http://global.wago.com/en/products/...tching-relay-optocoupler-859-series/index.jsp
 
taggr061362 said:
I have 32 small grippers on an unload arm for LSR injection machine. I have 4 banks of 8 grippers with sensors on each to sense they are in the open position. They use to make a 6 AND small card with 1 output that would work very nicely. The grippers remove a dump groove to avoid defective parts. I don't think I have room for 32 relays on the arm. Thanks for the information.
Click to expand...

We use the Banner MA4G for pretty much the same application:

http://info.bannerengineering.com/cs/groups/public/documents/literature/03351.pdf
 
One CMOS 4068 NAND/AND gate, a handful of 10K resistors, a 2N2222 and a transistor are all you really need.

Use the resistors as a voltage divider for each prox switch input AS WELL as the supply power, that will keep the chip operating at the same voltage as the inputs at all times. Drive a transistor with the output to convert back to your 24V logic. Done, about $5 including breadboard.
 

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