newbie question pls help

I need to operate a machine which will have 3 temperature inputs and 1 pressure input. I think i will need at least 3 dry contacts for outputs and a 0-10v output. I know nothing about PLC's but it seems like it might be the best way to do this so i can change settings easily. Could anyone recommend something cheap and easy to work with? I would really like to start learning this.

analog inputs are expensive, and this setup looks like you want a cooling system to control??
with Micro800 you can not connect a temperature sensor direct, you will need a converter.
Better to look further, as you need more money, or have a look at www.arduino.cc (i know it is not a PLC but it is cheap)
i work a lot with WAGO (as they have lots of modules available)

welcome to the forum.

before you buy anything, i would suggest the following.

think out your process in detail.
what is needed to start / stop / monitor the system?
what sensors are there - temperature, pressure, flow, water level, prox switches, limit switches?
what outputs will you need - 0-10 volts, 4-20 ma, solenoid valves?
don't forget spares, you almost always forget something.

think your process through and ask yourself questions.
it may be difficult at first, but it pays off in the long run
by not having to rebuy a larger system later.

regards,
james

to start and stop all i need is an on/off switch

one temp sensor will control a heating element on/off

another temp sensor will act as a high limit

id like a pressure transducer to open a solenoid if needed

in the future i may add another temp sensor to open another solenoid or possibly a 0-10 output for a modulating valve

i come from an hvac background and i know how simple this is to wire up with a stat and a couple relays but i would like to try with a plc so i can have more control and be able to add to it. im very interested in learning some basic programming and i think it would help me in my current job. i have a spare carel pco5 laying around but it seems like a bit of overkill and i want to start simple.

Thanks for your reply!!!!

James Mcquade said:

welcome to the forum.

before you buy anything, i would suggest the following.

think out your process in detail.
what is needed to start / stop / monitor the system?
what sensors are there - temperature, pressure, flow, water level, prox switches, limit switches?
what outputs will you need - 0-10 volts, 4-20 ma, solenoid valves?
don't forget spares, you almost always forget something.

think your process through and ask yourself questions.
it may be difficult at first, but it pays off in the long run
by not having to rebuy a larger system later.

regards,
james

Click to expand...

You might start with a programmable smart relay. It sounds like a smart relay could do what you mentioned.

http://www.automationdirect.com/adc..._(Stackable_Micro_Brick)/PLC_Units/C0-02DD1-D

Should do it for you.

john,

great work !

your next step is to determine if you want to use 120 volt controls, 24 volt, or a combination of both.

then look for a controller.
in that respect, what does industry use in the area you live in?

regards,
james

Hi,
Is there a way to read the operating voltage from Micrologix 1400 PLC?
Cheers,
Aryan

James Mcquade said:

john,

great work !

your next step is to determine if you want to use 120 volt controls, 24 volt, or a combination of both.

then look for a controller.
in that respect, what does industry use in the area you live in?

regards,
james

Click to expand...

24ac is all i will need for controls.

im not sure about industry in the area. we use carel and danfoss here but i work for a chiller manufacturer.

thanks for all the replies!

ok.
you have determined the voltage to be used and the plc(s) to use.

look at each brand and see what they offer.
are they expandable - something is almost always forgotten.
what is the price range of each?
do they offer software or is the units programmed from a hand held unit?

check with the local sales reps to see if you can get a demo unit to play with. if you can, that will help you with your decision.

regards,
james

Is there a way to read the operating voltage from Micrologix 1400 PLC?
Cheers, Aryan

Click to expand...

You could use a voltmeter to read the connected voltage. Another way is to get the "Allen Bradley MicroLogix 1400 Programmable Controllers User Manual" from the AB.com site. Page 2 has a chart that shows the operating voltage for each ML 1400 model. If I knew your model number, I would look it up for you. 4 models have 120/240 input power, and 2 models have 24 Volt DC input power.

Thanks Lancie for the reply.
I am looking for a way to remotely monitor the supply voltage to the PLC .
This way we will realize if the supply voltage for a remote skid is dropping to an unwanted level.
I am looking for a register or an Alarm tag in ML1400 to be able to read this voltage or receive an Alarm.
Thanks again for your time.
Cheers,
Aryan

...in ML1400 to be able to read this voltage

Click to expand...

If you have a 1766-L32AWA, L32BWA or L32BXB, then you could use one of the 0-10 VDV analog inputs to measure your voltage.

Assuming that your ML1400 is a L32 AWA, then you would need a voltage transducer with a 0-10 VDC output to change your 120 VAC power to a 0-10 VDC voltage signal input to the ML1400, so that you can measure scaled level.

On the other hand, if you simply want the ML to know if the power supply is on or off, and you have on of the MLs with 24 VDC input power, then you could simply wire power to one of the digital inputs to signal if the voltage is ON or OFF. That case is sort of trivial, because if the 24 VDC power is lost, your ML will go off anyway and the voltage level will be a moot topic.

To read a 24 VDC power supply voltage with one of the 0-10 VDC analog inputs, you would need a signal conditioner to change the 0-24 VDC IN to 0-10 Volt DC OUT, then send that signal to your ML1400.

So, you mean there is no internal register or an alarm tag which I can use for this purpose?

Yes, certainly internal registers that you can use to read the voltage input level, but you have to convert the voltage to a level that the ML1400 can handle. Do it without that and you are going to let the smoke out of the analog input.

There is no pre-programmed single-purpose ML1400 Status register that will tell you the voltage level of your input voltage. It is a "programmable" controller - you have to program what you want it to do, and it can send out an alarm based on a voltage level, but that is not pre-defined or pre-programmed.

Which ML1400 model do you have, and what is the power supply input voltage?

Does your ML1400 have any add-on modules, such as maybe a 1762-IA8 analog current input module ?

Once you convert your input voltage to a signal that your ML1400 can read and understand, then you can develop any kind of alarm notification that you want in your internal program. However, if the voltage is really dropping fast, your alarm may be short-lived. You may need a separately-powered alarm device (instead of using the ML1400) to prevent losing power to the alarm device itself. Another option would be a small UPS to power the ML1400, so that it would have time to sound the alarm before the UPS battery went dead.

With a small Uninterruptible Power Supply feeding the ML1400, then you could wire an analog input through a transducer to the UPS input power. Then when that dropped, the UPS would keep the ML 1400 alive so that it could sound the alarm. Of course, many small UPS units have a built-in alarm output (battery powered) for that very purpose.