hey guys! I am new on these forums but I have been a lurker here for a while. I am trying to resurrect a high pressure pump from 1980s manufactured by a major Japanese company (shimadzu). The problem in reverse engineering the circuitry inside the pump is proving hard for me and I am looking for insights at how to make things a bit easy.

essentially, the the pump has a stepper motor and that is controlled by a circuit which is connected to a pressure transducer which can control for constant pressure or constant flow rate. The circuit has has to do compressibility correction which uses a very easy mathematical expression.

I am attaching a user manual; the second last page has the circuit diagram for the original circuit.

we used to control the pump by using national instrument USB 6008 and through a labview program which interfaced this pump to other aspects of our equipment. the problem is that the inner circuitry of the pump is toast and I am trying to design a new circuit using microcontroller boards or whatever you guys suggest and program it instead of relying on old school 1980s analog ICs.

 

If your USB 6008/Labview can generate step/direction signals then an off the shelf stepper driver (Gecko,etc..)/power supply may be all thats needed..
I doubt I'd remake the whole control board when stepper drivers are cheap/off the shelf

 

mcgyvr thanks for your reply. let me say that before you reminded me of USB 6008 that we already have here, it didn't even cross my mind to look at it for generating step signals. I was so engrossed at remaking the whole control board from the original manual that I had overlooked at the bigger picture. I am a chemist and while I have gathered some electronics and programming knowledge along the way in order to keep our equipment running and maintaining it long after the manufacturer support has ended; I definitely found understanding this circuit and making this project work extremely intimidating and hence I apologize if I happen to ask rather stupid questions.

I think USB 6008 can generate square waves however I dont know if its resolution will be good enough. I am attaching its datasheet: http://www.ni.com/datasheet/pdf/en/ds-218

another question I have is that the stepper motor has to be controlled to give two alternate outcomes: constant pressure or constant flow rate. Now, I have gone back to the original circuitry and I still haven't figured out how they are controlling for constant flow rate. For constant pressure, they are just using the output from the pressure transducer as a signal.

I don't have a full spec on the stepper motor except to know that its max current is 3.6A and its a four phase stepper motor. I can open the pump and try and look for any further identification marks. Can you suggest any stepper driver in particular that I should be looking at?