Is a PLC the right way to go in this case?

Fasthotrod said:

I'm sorry... I don't follow you.

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The thermocouple module for the DL06 is $199.00 for 4 channels. Figure about $26.00 each for thermocouples. In rough figures, this is about $75.00 per channel. With other methods, it can cost up to $200.00 per channel. If you were tearing out a bunch of electronics, I was trying to give you a ballpark replacement figure. I expect the thermistors and amplifiers to cost much more than that, and the thermocouple (T/C) & PLC method is the lowest cost.

The DL06 is a very powerful unit. Searh this site for many positive comments on it.

Since he plans to use Modbus to get all the data from the genset he should not need any analog input, the only issue may be sending the 0-100mv signal to the legacy device, not sure you can output that from a plc but it could an use an analog out with a signal conditioner if necessary.

SLC Integrator's comments re setting up Prosoft modbus cards raises one of my pet hates. I actually find the CLX and FlexIO cards very easy to set up but this is only after struggling for many hours with what must be among the worst manuals ever produced. The manuals are huge and are full of minute detail on the methods used to pass data across the various PLC backplanes but finding the information about things which are actually relevant to the user can be very difficult. Prosoft would do themselves no harm at all by providing a "Quick Start" type of document. This said the cards actually work well and once you have set one up using them becomes much easier.
Andybr

Good morning, guys!

Keithkyll: Ohhhh... I understand what you are saying now. That makes complete sense to me now. Thanks for the clarification. :nodi:

RSDORAN: I was looking at that, and I wondered if I could use a 0-5 or 0-10 VDC signal and a resistor network to create the voltage drop I am looking for.

For example, I could use the 0-10 VDC output across a 10k ohm circuit for 1mA output at full scale. By using multiple resistors and potentiometers, I can tap into the circuit for my 0-100 mV output. I will need to make it adjustable so my external circuit impedance can be taken into account... but that shouldn't be too hard.

Or... I could just buy the signal conditioner that you recommended! Do you happen to know what they cost?

Andybr: I hate it when a company puts out a great product, only to cripple themselves with a poor document. I might have to pick your brain when I get into it!

Good news:

I just finished talking to my team lead, and I think I have him convinced to bypass the input amplifier cards and install a "pass-though" circuit card that connects to the backplane. At the backplane, the legacy system is looking for 0-5 VDC, and would make my life so much easier!

So far as I can tell, I would need at least 12 0-5 VDC outputs... or I could use the 0-10 VDC outputs and program it to max out at 5 VDC. (I assume I can do that... am I right?) If not, then I'll have to come up with a resistor network and look at the voltage drop.

From looking at the manual for the AD DL06, it has the I/O I would need for my alarm indications. I'll probably go with relay outputs vs. sinking/sourcing to keep it simple... unless you guys think it's better to go the other route. Opinions?

There might be a few other things that pop up... but so far it looks like I'm going to go with the AD DL06 for this project. Two F0-08DAH-2 Analog Voltage Output modules should provide the outputs I need to send the signals to the legacy system. The AD DL06 looks like it has two communications ports already... so I might be able to tap the RS-485's from the E/G and ATS with the PLC. I can always add another port later if I need it.

That being said, is it worth it to buy the LCD display that goes right on the front of the PLC? For $73 I might just buy it for the initial setup to see what benefit it could be.

Let me know if you guys think I am missing anything.

Best regards.

Mark

So far as I can tell, I would need at least 12 0-5 VDC outputs... or I could use the 0-10 VDC outputs and program it to max out at 5 VDC. (I assume I can do that... am I right?) If not, then I'll have to come up with a resistor network and look at the voltage drop.

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Yes you can program it for 0-5v.

There might be a few other things that pop up... but so far it looks like I'm going to go with the AD DL06 for this project. Two F0-08DAH-2 Analog Voltage Output modules should provide the outputs I need to send the signals to the legacy system. The AD DL06 looks like it has two communications ports already... so I might be able to tap the RS-485's from the E/G and ATS with the PLC. I can always add another port later if I need it.

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The DL06 can do Modbus TCP/IP, if your genset controller can do that then no problem, but the serial port and Modbus is there too.

RSDORAN: I was looking at that, and I wondered if I could use a 0-5 or 0-10 VDC signal and a resistor network to create the voltage drop I am looking for.

For example, I could use the 0-10 VDC output across a 10k ohm circuit for 1mA output at full scale. By using multiple resistors and potentiometers, I can tap into the circuit for my 0-100 mV output. I will need to make it adjustable so my external circuit impedance can be taken into account... but that shouldn't be too hard.

Or... I could just buy the signal conditioner that you recommended! Do you happen to know what they cost?

Click to expand...

Cost for the signal converter I expect would not be cheap but don't know exact cost. The only issue may be the legacy system may be looking for a specific type 0-100mV signal like those from thermocouples etc., not sure if the plc can duplicate that. Maybe Tom or one of the other AD gurus could answer that.

To me though that will probably be the only hard issue, the rest should be fairly simple.

Fasthotrod,

In today's arc flash enviornment the LCD display is of little use. Most programmers hate them. Some like them. I have several that I had to cut "windows" in the door so they can be viewed with the door closed.

Regarding the sinking sourcing VS relay outputs, relays are good when there is not a lot of on off (My rule of thumb is if it's less than once a minute then use the relay out)

By using the new 16 bit 8 channel out cards you will have to scale them in your logic to only give you 5 volts out or use a resistor network to cut the voltage in half. The good news is that even if you only use half of the output you will still have more resolution than the old 12 bit modules that are configureable for 5 volts or 10 volts.

IF you need to go Modbus RS485 to Ethernet i can recommend the Square-D EGX:

http://www.powerlogic.com/products.cfm?id=17

We use them on every job and they work very well

rsdoran said:

Yes you can program it for 0-5v.

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Sweet!

The DL06 can do Modbus TCP/IP, if your genset controller can do that then no problem, but the serial port and Modbus is there too.

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The equipment is equipped with RS-232/RS-485 standard, but has an adapter for MODBUS to Ethernet available. (I have one at my desk right now.) It might be worth it to run everything to a hub and communicate via MODBUS TCP-IP depending on the cost of the converters from Kohler.

Cost for the signal converter I expect would not be cheap but don't know exact cost. The only issue may be the legacy system may be looking for a specific type 0-100mV signal like those from thermocouples etc., not sure if the plc can duplicate that. Maybe Tom or one of the other AD gurus could answer that.

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The 0-100mV is a simple DC input. The 5 VDC signal comes from the legacy amplifier card, through the oil pressure sensing device, and back to the amplifier card. If I can eliminate the legacy amplifier card and just tap directly into the backplane, then all I need is 0-5 VDC to make the circuit work. If I can grab the oil pressure from the MODBUS TCP-IP, then I'm left with sending a proportional 0-5 VDC output from the PLC to the legacy system. I am going to push in that direction to avoid the aditional circuits and related costs.

To me though that will probably be the only hard issue, the rest should be fairly simple.

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I certainly hope so. As I said before, I am ignorant to programming PLC's but I can't wait to learn about it. I'm sure I'll have a few bumps in the road, but it sounds like you guys have all "been there-done that" before. I'll be picking your brains for sure! :nodi:

Mark

milldrone said:

Fasthotrod,

In today's arc flash enviornment the LCD display is of little use. Most programmers hate them. Some like them. I have several that I had to cut "windows" in the door so they can be viewed with the door closed.

Click to expand...

But the LCD panel looks cool!

Okay... so skip the LCD display panel. I'll be programming from my laptop anyway, and there really isn't a reason to view the PLC info as the legacy system provides everything that the user needs to see. (As do the E/G and ATS control panels.)

Regarding the sinking sourcing VS relay outputs, relays are good when there is not a lot of on off (My rule of thumb is if it's less than once a minute then use the relay out)

Click to expand...

The only time I will activate a relay is when the system changes state. That only happens when the power goes out, or I have an alarm indication when the E/G is running. Less than once a week for a power outage, very few times for the alarms I would hope.

Sounds like I go with the relays.

By using the new 16 bit 8 channel out cards you will have to scale them in your logic to only give you 5 volts out or use a resistor network to cut the voltage in half. The good news is that even if you only use half of the output you will still have more resolution than the old 12 bit modules that are configureable for 5 volts or 10 volts.

Click to expand...

Good to know, thank you. If I can use the outputs as 0-5 VDC and let the software handle everything, then I'll be a happy camper. (The fewer components, the better... I like to keep it simple.)

Speaking of simple... I have the choice of using 120 VAC or 24 VDC from my power system to power the PLC. I have both sources available at the site... is there a drawback from choosing one over another?

Mark

The 24vdc is considered to be safer but either way since this is going to be dealing with a genset I would have it on a UPS and let it run 24/7 whether the genset is running or not.

Fasthotrod,

The deciding factor on weather to use 24 volt vs 120 volt might come down to the "power budget" as AD calls it. The 120 volt units have more overhead than the 24 volt units. You have to add up the power consumed by each module (details are in the catalog).

Arc flash may also apply. As the 24 volt unit does not require the "space suit".

So it looks like I'll by purchasing the following equipment:

One AD DO-06AR PLC: 120VAC w/Relays
One Programming Cable
One DirectSoft5 Software package
Two FO-08DAH-2 8 Channel Analog Output cards
One Users Manual

Total: $1078.00

I'll pick up a CR2354 battery locally for $3.99 vs. $12 at AD. :nodi:

The price seems pretty decent from what I can tell. Is there a huge price difference between this setup and say one from AB or another company? (With the same features, obviously.)

Once I get everything and get playing with it, I'll be back to pick your brains on how to get this project off the ground.

Thanks again for the tips and suggestions, guys. I really appreciate it.

Mark

The AB programming software alone would cost more than what you have already spent.

Without going back over previous discussions, in general the more you pay the more 'features' you get built in to the hardware/software.

Alot of folks are comfortable or actually prefer writing their own custom stuff so dont mind getting an 'empty box' so to speak.

Fasthotrod,

I find the DN-15TB terminal block and the ZL-DN15TB-CBL an easy way to wire the PLC to your RS485 cable.

OK, the nitty gritty is out of the way, lets get to wiring this thing and get it going.