I/O module suggestion

Hi All,

Does anybody can give me a suggestion about using a digital output module type on SLC processor.
When I must use relay type (1746-OW16), solid state type(1746-OB16) or Triac type (1746-OA8).
Any advice would be appreciated.

Thanks in advance

Deer

Hey Deer,

I'll try and answer, I don't have an rslogix program in front of me, but can offer some information on 2 of the 3 you are asking for...

The triac, is mainly for 120 vac switches. If your eyes, etc... are using 120 vac for a signal, this is the one you wish to use.

The OB16, check that one carefully. If I remember, that is a 24 VDC switch, and you will need to make sure if sinking or sourcing. Lately, this has not been an issue, since most newer photoeyes will allow either way for a signal to the plc. Just make sure you are setting up proper, or you could overload the switch or card...

As for the OW16, for the life of me, can't remember what that one is... Check your I/O configurations on the rslogix program, the window on the far left, and they will list every module available for the Slc, with a brief descriptor. I have found them quite useful when designing a setup.

Also, if you are using, say a 120 VAC switch and only have 24 VDC cards or modules, you can setup a simple contact relay to save a few $$$. Set the switch up with the coil on the contactor (120 VAC coil) and then use a simple transformer (120 VAC to 24 VDC) and use the output from the transformer to the input of a contact on the contactor, then the output on the contact going to the plc. When the switch is in a 'closed' state, it will activate the coil, making the 24 VDC wire go 'closed' also. Thus, sending the proper voltage signal to your PLC.

Deer, also make sure and pay attention to the sinking and sourcing lables on your setup and literature. Allen Bradley views their cards as the 'start' of the signal. This does lead to some confusion with a new setup...

Hoot

When to use what?????

When I must use relay type (1746-OW16), solid state type(1746-OB16) or Triac type (1746-OA8).

Click to expand...

Looks like you know what these modules are and that is half the battle. Picking which one to use is based on what you want to do with it and how the machine is wired. You have to match your output module to the voltage and current rating of the loads you intend to control. Using the the OA8 for example, you would be using a single 120vac control voltage, or two separate supplies, and making all your operate in two groups of 4 or all 8 together on the same supply. The OA8 is an eight output module with two 120vac hot connections and therefore can be operated on a single or dual supply system. The OA16 has two sets of 8 outputs that may be operated on two separate 120vac systems. If you want to use the OW16, it really gives you some flexibility. Since the switches are relay contacts, they will fit several different voltage and current applications. They are also arranged in two groups of 8 outputs on a single common. The OB16 is similar to the others but is intended for low voltage control due the outputs being transistor type. Just check the specifications and do not go over the limits of voltage or current and you will be fine.