5V TTL Open Collector Output to PLC

Hi there,

I have a 3 x 5V 100mSec open collector TTL outputs I need to capture in a Micrologix 1400 plc. Similarily I want one 24V output from PLC stepped down to 5V for input to same TTL device.
Can anyone please advise me on the best way to approach this? Am I correct in saying that the current 0.12mA will not be sufficient to use relays? Also this could introduce further delay?

Thanks

which PLC is it 7166-L32 ______ ???

This determines if you can direct connect, use pull-up resistor or need to add an SSR interface.

For output use a 5K ohm POT or 2 resistors (1.2K and 4.8K in series) for a voltage divider network to pick off the 5 volts. (don't forget to glue the knob on the POT so it doesnt get turned and blow out TTL

1766-l32 _____

[email protected] said:

which PLC is it 7166-L32 ______ ???

This determines if you can direct connect, use pull-up resistor or need to add an SSR interface.

For output use a 5K ohm POT or 2 resistors (1.2K and 4.8K in series) for a voltage divider network to pick off the 5 volts. (don't forget to glue the knob on the POT so it doesnt get turned and blow out TTL

Click to expand...

Its an 1766-L32BWA. I can use an alternative if it supports direct connect and not a huge difference in cost. As long as I have 2 RS232 ports and Ethernet I'm happy!!!!

How can you connect a 5V TTL to 24VDC input? Would input threshold not be a lot higher?

Never used SSR's before. Is is a small load? I think my output current is about 0.12mA.


How about a darlington driver circuit?

Open to any suggestions!!!

If you use a voltage divider with 24 volts feeding input cross the resistor bridge and the 5V TTL pulling down the input it can invert the signal but draws a lot of current. This could burn out the sensor. (I did it with an encoder and it worked for 6 months then killed encoder as I picked resistor value too close). Better to use a 5 Volt coil relay.

I think this relay will fit into slim relay bases designed for 24 VDC sockets so your panel will look industrial.

see www.factorymation.com "slim terminal block interface relay" they are interchangeable with allen bradley and phoenix contact relays and bases and might fit something like what i suggest below.


You can get them anywhere but surplus from www.allelectronics.com is

5 VDC SPST N.O. DIP REED RELAY​

Magnecraft # W117SIP-6. S.P.S.T.,
Normally-open, reed relay. 5Vdc,
500 Ohm coil w/ clamping diode.
Rated 10VA, 0.5A switching and can carry up to
1.5 Amps. Four in-line pins, 0.2" between pins.​

CAT# RLY-541​

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and a link to converting 24vdc to 5v with pullup. http://www.mp3car.com/vbulletin/hardware-development/96491-how-convert-24vdc-ttl-5-vdc.html