Analog pump control

[brown2169]

How can I convert a analog signal to fire a digital output to run a pump?
Also what would the logic look like?

using micrologix 1763-l16-dwd
analog signal is from a ultrasonic transducer 4-20ma

 

[MartB]

How can I convert a analog signal to fire a digital output to run a pump?
Also what would the logic look like?

using micrologix 1763-l16-dwd
analog signal is from a ultrasonic transducer 4-20ma

You might want to explain your process a little more.

Take the analog signal, compare to a value (possibly use a greater or less than comparison), if true set an output.

At this point I can only guess as to what it is you are trying to acheive, more detail would be helpful.

 

[Mickey]

With a little more info we can give a little more help.
Have you scaled your analog input, to?
Do you want the pump to come on above value "X" or below value "X"or both.

Use instructions below:

MartB, you type faster.

 

[Paul T]

Well, a little more info would be helpful. Are you trying to do level control in a well or tank? Are you trying to do flow control with a pump and VFD or valve (probably not, since you didn't mention any...)

Level control is pretty simple. Monitor the analog output, and when it goes too low (if you're trying to fill) or too high (if you're trying to empty) that triggers an output to the pump. You need to latch that in, with the opposite end of the analog output to break the latch when the tank is full (or empty).

Lots of ways to do it... if you were trying to fill a tank, you might try something like:

Rung 1 - If (AnalogOut < LowLevel) B3:0/0 On
Rung 2 - If (AnalogOut > HighLevel) B3:0/1 On

Then

----||-----|-----|/|---------( )----
...B3:0/0....|....B3:0/1..........O:0/0
----||-----|
..O:0/0


This is a pretty standard circuit... if this was a homework problem you're welcome. If you're doing this for real, then just start playing with your ladder package; it gets easier the more you do <g>.

 

[brown2169]

I want to use an analog input to control a well in a pump down situation.

setpoint A - low level
setpoint B - lead pump run
setpoint C - lag pump run
setpoint D - high level alarm

I am not very familiar with analog inputs and don’t know how to scale them. Basically if someone could tell me how to turn it into a digital input or value I could do the rest of the programming with out much difficulty.

Thanks for your qick response's

 

[Mickey]

Just a little more info.
The ML1100 has two on board analog inputs( 0-10volts), are you using one of those or do you have an expanison module ( if so which module do you have i.e. 1762-IF4? 1762-IF2OF2? and what slot is it in 1,2,3,4).
You can use the SCL or SCP scaling instruction to scale your analog input.
I prefer the SCP.
Setpoint B&C: Does the pump come on on a increasing level or decreasing level.

See PDF, made some assumptions, using I/O module 1762-IF4 and pump comes on on a increasing level.( bad I know). Very simple control no bells and whistles.

 

[brown2169]

I was counting on using the on board analog inputs and the pumps come on using increasing level.

Thank's Mickey your diagram has been very usefull.

 

[Mickey]

I was counting on using the on board analog inputs and the pumps come on using increasing level.

Thank's Mickey your diagram has been very usefull.

Be advised the on-board analog input for ML1100 is 0-10 volts only and the resolution (raw data) is 0-1023.
You can run your 4-20ma thru a resistor to get voltage then connect to ML1100, 250 ohms gives you 1-5 volts, 500 ohms give you 2-10 volts. Hope this helps.

 

[brown2169]

If I use te 500ohm resistor what would my scale change to?

 

[Mickey]

If I use te 500ohm resistor what would my scale change to?

What does your 4-20ma represent (scaling of your level transmitter)?

With a 500ohm resistor and a 4-20ma input you will get 2-10 volts.
4ma = 2 volts = 204.6 (205) ( raw data)
20ma = 10 volts = 1023 ( raw data)

If you scale your level to 0-100 ( your scaling may be different) then see pic below

 

[brown2169]

Alright I got the analog part figured out. Next what device would you use to set up pump alternations on the same system?

 

[ELake20]

Explain the alterations you need to make to the pump....
I love using the LIM instruction and this may be a good application to use this.

 

[Mickey]

If by alteration you mean rotate lead/lag of pumps ( "A" lead/"B"Lag or
"B"Lead/"A"Lag") then.
Using the example I gave before. Instead of using constants for the setpoints I use a variable data file. See PDF
What controls the Lead/Lag control bit can be time,Manually done, Fault condition, all the above or what ever you want.
This is just one way. There are many more I'm sure.
Example has no bell and whistles, no what if conditions (i.e what happens if pumps are running and the lead/Lag seq. is changed)?
You cannot think of all what-ifs but give it some thought.

 

[brown2169]

Thanks Mickey that makes perfect sense. But how would I control bit B3:2/0 to change states after each run? That way each pump runs every other turn. Maybe a latch bit tied to pump A and unlatch tied to pump B ?


Thanks again for your help

 

[Mickey]

Write the logix and post it here someone will take a look.
I have done it different ways, one is with the flip-flop logic ( do a search for that here you will get many hits). Another is if you have running status you could count starts, then compare and make the one with the least amount of starts the lead unit. Another would be to increment a counter each time both units stop,compare the counter accumulated value at 0 pump "A" is lead at 1 pump"B" is lead.At three
reset the counter back to zero.
Give it a shot and post it.