Re: New to EPICS - system design questions

[Ryan Pierce <rdpierce@pobox.com>]

I've been interested in experimental high energy physics since I was a kid. While my career path took me in a different direction, I got involved in the maker moment and the PS:One hackerspace two years ago, and have been doing nuclear tourism. (I live a few blocks from a certain former squash court, made a trip to Chernobyl in 2013, and saw the Hanford B reactor last week.) It's definitely a different way of learning. I independently rediscovered integral windup when I disconnected the chiller keeping our fermenting beer cold. When I reconnected it, the PID loop I designed tried to freeze the beer! I also got PS:One a donated scanning electron microscope with EDX detector that I now maintain, so I guess in a way I ended up doing accelerator physics after all, just with a 30 KeV beamline. ;-) To my knowledge, we are the only hackerspace with a working SEM.

I'm trying to promote science at PS:One with the SEM, member projects, an applied sciences lecture series, etc. I'm definitely interested in getting speakers from places like Argonne to come to PS:One.

Regarding EPICS, I attended an Argonne open house a year or two ago and was very impressed with the control screens used to run the APS. I saw a sign mentioning EPICS by name, and a demo of it running a PID controller tuning a microwave cavity. Talking to people there, it sounded exactly like what I was looking for.

Thanks to everyone who provided info that I will be sifting through.

Cheers,

Ryan

-------- Original message --------

From: Michael Davidsaver

Date:08/12/2014 7:54 AM (GMT-06:00)

To: Ryan Pierce , tech-talk@aps.anl.gov

Subject: Re: New to EPICS - system design questions

Ryan,

If you don't mind my asking, how did you find out about EPICS?  It isn't
exactly a household name.

I ask because my own introduction to control systems began with a summer
of re-inventing this wheel (poorly) because I didn't know what had
already been done.

Michael


On 08/11/2014 02:22 PM, Ryan Pierce wrote:
> I'm new to EPICS and am interested in putting it to some possibly unique uses. I'm a member of the Pumping Station: One makerspace in Chicago, which is a large non-profit community workshop with all sorts of tools (wood shop, machine shop, welding, electronics lab, CNC fabrication equipment, etc. and a scanning electron microscope, which I coordinate maintenance and training for) where members can collaborate and work on projects.
> 
> I'd like to use EPICS to control a custom all-grain beer brewing system I am constructing. I'm considering using an Arduino variant to do all low level hardware control, e.g. commanding valves, pumps, propane burners and/or heater elements, reading temperature, pressure, and flow sensors, etc. I'm guessing this would communicate via serial to a Raspberry Pi, which would run an EPICS IOC. I would use a laptop (or tablet?) networked via WiFi to the Pi as the control panel.
> 
> I know this sounds kind of strange, but the more I think about it, the more I like the idea of not having to write networking code or GUI for a control panel. Everything about the brewing system abstracts logically to process variables. I'm starting through the archived video presentations on a EPICS, and I'm wondering what best practices are for some of these things which I'm sure would also be used for more traditional science applications.
> 
> PID control: Code it on the Arduino, and expose the set point, PID constants and state over serial to the Pi, which exposes these as process variables? Or have the Arduino just expose the raw sensor data to the Pi, which exposes them as process variables, and run a separate process on the Pi that is an IOC publishing set point, PID constants, etc. that in turn reads and commands the lower level process variables? Or does EPICS have constructs for this already?
> 
> Ramp / Soak: this will drive the PID set point. I'd need to program profiles in with multiple temperatures and times. A process on the Pi maybe?
> 
> Event sequencing: I see EPICS has support for this. I'm not sure where to implement functions like "Add X quarts of water to the tank" where it would need to open a solenoid valve, count pulses on a flow meter, and close it when the level is reached. Or higher level sequences, like "first, fill the tank with X quarts, then heat it to this temperature and hold it there via PID, then prompt the user to dump in the grain, then run this ramp/soak profile", etc.
> 
> Alarms: I need the concept of multiple alarms that can be acknowledged / overridden. (Time to add grain, time to add hops, the pump flow rate dropped too low, etc.) I'm guessing this is a common problem and am wondering if there are already common solutions for this.
> 
> I'm interested in "async"; I'm wondering if this would make things easier by handling serial communications with the Arduino and allowing me to publish PVs on the Arduino without writing custom IOC code on the Pi.
> 
> Is MEDM still the way to go for control panels? I'm also wondering if there are any EPICS compatible control panel apps for IPad or Android tablets.
> 
> I'd like to publish data to the web so interested people can see the state of the brewing. Is there any kind of framework for publishing EPICS PVs to the web without having to write lots of custom code?
> 
> Anyway, I know this is unusual, but it sounded like a fun project to me. I think it would be interesting to see what would happen if EPICS and the maker community intersected.
> 
> Thanks,
> Ryan
>