PID Control Done in a Snap

A thought came to mind that when I need a PID controlled process or something on the side of industrial automation I just take an old “recycled” controller that was bound for the garbage heap and I make whenever I need. That’s great for me; my blog readers, not so much. I recently replied to a posting on an electronics forum with a guy looking for a cheap and easy way to control is variable frequency drive (VFD). This is a device that varies voltage and frequency to vary the speed of a motor. You can buy these in single phase for fractional HP motors thought they’re more commonly used in three phase applications. The poster was looking for a way to vary the control voltage (0-10V). I bit my tongue through the comments from people misunderstanding that it was control voltage an in fact the guy didn’t need a 10V 300A power supply. In his case he wanted to manually adjust the speed, but if it was to be an automated process and if I was him; I’d used a stand alone PID controller. These controllers are great for a pool pumps, hot water solar panels, exhaust fan controls, or something along those lines. I would use the Johnson Controls System 350 series controller. http://www.johnsoncontrols.com/content/us/en/products/building_efficiency/commercial-refrigeration/system-modular-control/350controls/a350/sysa350p.html

System 350 PID Controller
System 350 PID Controller

You can get these to control off temperature, humidity, or pressure to vary your output. They also come in staged outputs. I’ve seen these for green house controls, water pump VFDs, etc etc. It’s pretty simple; have a control sensor, and command an output, adjust the set-point and proportional band/integration to “tune” the loop.

Full disclosure: I work for Johnson Controls, However! I do not/can not sell or install these. These are generally installed by electricians but trust me.. anyone could install one of these. I’ve played around with them from a condenser deck we were working on one time. You can pick them up at grainger or anywhere you can buy HVAC components, likely eBay as well?

.. also forgive the liberties I took with “PID”, I do realize it’s only a PI controller. It’s rare to find full PID implemented in an industrial or energy automation controller; we usually don’t need to use derivative.

Back to magnetic basics

I was picking through my pile of books which I want to get to sooner-than-later and read through a bit of Field and Wave Electromagnetics. I decided I shunned magnetics and inductors too much when I was in school and decided I needed to suck it up and become better versed. The last time I worked with any type of inductor was my home brew 6 meter 4-400 amplifier.

Shown in the image is just a LM555 configured as one shot attached to an IRF530 which I originally had a driver but realized it was pointless as I could run the 555 at 12V and it would work just fine. This configuration was 5A which is too much for my breadboard but not a big deal at 10ms.

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Soldering Large Connectors

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When it comes to soldering large connectors on LMR400 or larger you owe it to yourself to have a large soldering iron. This ancient beauty has a lot of thermal mass and really gets the job done. I borrowed this from my good buddy Gary for some large work. You’ll likely need to visit eBay to pick up something like this anymore.

Raspberry Pi Give-Away

Fish Fry announced that they are giving away a Raspberry Pi B through Element 14. If you have the time there is a short interview about the Gertboard add-on or whatever you want to call it with Gert van Loo  — More information can be found on google or my favourite place https://www.sparkfun.com/products/11773 Not an intentional plug for sparkfun; I don’t have any sponsors or any of that nonsense.

Check out the details on the Raspberry Pi give away at:

http://www.eejournal.com/archives/articles/20130510-fishfry/ (opens in new window)

I should probably do more tinkering than posting but I am waiting until I go back to South Dakota and work on my farm house were I have a few LCD monitors ratted away. We only have laptops now so I can’t boot up my Pi yet. I’ll bring it with me to keep me company on those cold nights. T-minus 12 days. Lately I’ve been tweaking on my Tektronix FG 501 signal generator. I’m attempting to make it sweep but my voltage ramp circuit is apparently crap. I should just suck it up and buy a better piece of equipment; I’ll start eBay lurking. The FG 501 is an excellent signal generator if you can find one. My FG is in a single unit cabinet although you can buy multi-bay backplanes for these plugins and that’s where they get fun! Too bad it’s usually expensive and really I should be saving up for something that could be calibrated. I wish Fluke had something decent in FGs; I have an inside connection on heavily discounted vendor returned items.

Electronic Hobbyist

I was looking for some interesting news sites for electronics as I do from time to time. Not much out there… well at least none with articles that were of immediate interest to me.

I came across this article and nearly commented but it was from 2007 with zero comments, so there wasn’t much point:

http://electronicdesign.com/archive/whatever-happened-electronics-hobbyist

I’m an amateur radio operator/builder, I like building embedded systems and I’ve built a robot, so I guess I get to fit into all three of his “types” of electronics hobbyists of the future. I think he’s probably right on with the separation of electronics hobbyist .. unless you count students; I wouldn’t. Is that a big deal? I don’t think so. Technology had made it difficult to take the old “easy” kits to offer to youth to spark some interest. Who knows how long AM will be around? Give it a decade and someone will be leaning heavy on the FCC to shut it down and sell off the spectrum. AM isn’t making any money these days.  This article also feels a little “back-in-my-day” which gets eye rolls from anyone under 40.

So my only real beef with this article is his opinion that QST is a quality magazine that supports electronics hobbyist… I totally disagree. QST isn’t worthy of toilet paper in my opinion. It’s the ‘US Weekly’ of electronics magazines. All Ads, back-in-my-day articles, and sponsored reviews. QEX on the other hand is an EXCELLENT magazine, we are in agreement there. I would recommend QEX from non-hams if they’re looking for more reading material as there are plenty of projects that could be re-purposed.

If anyone coming across this happens to have some “favorite” generic hobbyist news feeds drop me a comment. I’m always looking for interesting articles.

 

 

 

 

 

Deception Pass State Park

Melissa had the weekend off so I had to opt for a low accent hike and semi-scenic. I had never been on North Whidbey Island so we headed out this morning. Not the hike for those seeking solitude… But a nice beach walk was included and really it was 80 on a May weekend… There were going to be people everywhere… Back to the Raspberry Pi tomorrow… Going to configure it and perhaps I’ll try out a few of the OSes.

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