Feed pump controller

[raghu670]

Hello, I am looking for a feed pump controller that will allow me to feed my process vessel automatically as my culture grows and demands more feed based on scale weight.

I want the controller to ramp according to an exponential equation and should be communicatiog between Mettler Toledo scale and Watson-Marlow pump.
Any help in this matter is of great help
Thanks in advance
Raghu Philkana

 

[danw2]

Is this a continuous output controller? Where the pump is always feeding something to the load?

What are available outputs of the scale and input of the pump?

pulse input on the pump?
4-20mA? Modbus? proprietary digital protocol?

What weight range do you have to cover?

 

[richs]

Hiya-

Yes, we need the selected interfaces of the scale and the power requirements for the pump, in addition to the continuous feed of the pump and if continuous feed, how the interface to the pump is expected. The web site for the pump did not have interfaces easily available.

The scale (at least the XP/XS series) have a variety of interfaces available to it including:
RS232, Ethernet, Bluetooth, LocalCAN.

For a "bare bones" implementation, and if you don't want to get into the heavyduty "electronics" of the thing, I would suggest an old PC of some sort.

If it were me, I would use linux as the operating system, but I am biased. A windoze approach would be o.k. if you dont' mind the system crashing every now and then ;-)

I assume that with the brand names mentioned that this is in a lab environment and at this point, one is not doing industrial bio reactors.

A standard (old) computer kicking around can have additional advantanges:

1. Ethernet is often available. This, with the proper software can be used for remote data monitoring and modification to the parameters remotely.

2. With a hard disk, data collection and retention via either a data base or other data logging software can provide the record keeping of the process. I personally would use "Round Robin Data Base" (RRD) with scripts to collect the information from the scales and the amount of time the pump is activated.

3. A good user interface. The "monitor" of the machine need not be turned on all the time to save energy if that is requited. Real time graphing can be done and displayed on the monitor along with the keyboard to adjust parameters as required.

4. Depending on the pump interface, the parallel port can be used for generating an output to a driver to drive a relay to power the pump. Of course, you would lose the ability to use the parallel port for a printer, but most printers these days use a USB interface anyway.

All this, of course, requires the "special software". This may or may not be in your present collection of tools. However, a nearby "computer geek" might provide the necessary software skills to help you with your efforts. The process control software is not what the computer folks would call "real time". There is a very small requirements on the computer's performance to do this job. Except for the above mentioned advantages, the PC would be overkill.

If the geek is not available, you might look into some of the standard lab packages like matlab for a leg up on some of the stuff. Indeed, MATLAB might have drivers available for the scale already and then all you would have to provide is the equasion for driving the pump based upon the weight differential from the scales. You will still have the ability to do data collection, however, remote monitoring and control might not be available.

There are a lot of programming languages and scripting languages available for you to program in. Depending on what you know, will dictate the choice.

I hope that this helps.

Cheers,

Rich S.

 

[raghu670]

Hi,

We would like to have a continuous output controller. WE have to feed the bioreactor continuously for about 24-48 hrs using exponential equation.

Both the scale and the pump have RS232 and 4-20 mA output.
The pump we are using is a peristaltic pump.

The feed rates are 1gram/min to 200 gram /min for a 100 L reactor.

Thanks for ur reply
Raghu

 

[richs]

Hiya-

Well, the standard PC useually has a couple of RS232 ports on them. At least the older ones. You might want to use those and not have to resort to a 4-20ma interface.

Cheers,

Rich S.