Created Date: December 24,2013

Created by: jwbaker3

I would use the 120 volt powered base and install a UPS on the system for backup power to the PLC and the HMI if it is required. I never use the power supply on the rack to power analog, I use a separate power supply with good grounding and only power the analog with it to lower the noise. I will use the rack to power DC I/O, keeping the power budget in mind. Either rack will work fine but this is the way I would do it. For what it is worth I would use the Do-More CPU, it cost a little more (unless you need ethernet then it is cheaper that a DL CPU and a Ecom100) but I more than make it up the higher cost with less programming labor.

JW

Created Date: January 09,2014

Created by: mike42952

I would use the 120 volt powered base and install a UPS on the system for backup power to the PLC and the HMI if it is required.

JWBaker;

Thanks for advice. I agree on the Do-More, haven't used it but it looks nice.

Have you ever used a configuration like this: 24VDC power supply -> 24vdc battery controller-> 2x12V batteries (in series for 24vdc) -> 24VDC consumers (PLC chassis as 24v, analog and DC loops).

Does the above make more sense than using a 120VAC (in/out) UPS like an APC or Tripplite?

Created Date: January 09,2014

Created by: jwbaker3

That should work. Other than mobile systems I have not used batteries as the backup power and without knowing your systems needs I cant say if this is a good choice. This system will power the PLC longer during a power outage, if that is what you need? I think the equipment cost will be higher. Unless every thing runs off the battery backup I don't know the benefit, but I don't know your system. Do what works, is safe, meets the needs of the entire system and the customer as cost effective as possible, it's always a balancing act to do this. We try to look at a project as the whole, apply sound engineering to the mechanical, electrical and automation systems so they all work together to meet safety requirements and the goals set by the customer. Sometimes that means doing something on the automation side that most programmers would think is too costly or not needed, but makes the system work.

JW

Created Date: December 23,2013

Created by: mike42952

Hi,

I am specing a PLC for a small project, and I have a choice of either a 120vac chassis, or a 24vdc chassis fed from a separate 24vdc power supply. Either way I will have 24vdc power supply (for 4-20ma and analog devices), but the 120vac chassis are slightly cheaper (i'm looking at the DL-205 series), so I'm not saving anything by using the 24vdc chassis.

Which is the better way to go?

I realize that with 24vdc you can use a battery backup more easily (even though you need a separate battery controller), but then 120vac UPS systems are pretty common and cheap nowadays.

I'm hoping for the advice of someone more experienced then me.

thanks