Looking for Ready made stand alone DIGITAL PID.

No ideas. Some comments.

I'm not clear about exactly how you are using these PID units, right now. It almost sounds as though you are an off-the-shelf consumer of PID controllers with a specific process to control -- except for the fact that you talk about unipolar and bipolar operation being a plus, which suggests that you have a variety of situations to deal with and not just the one. That makes me imagine you more in the position of not really knowing where the PID is being applied and that you want a more general solution as an OEM supplier to end users (which implies you aren't the end user of the PID.) Are you and end-user or do you supply something to others that must include PID as a feature?

You also mention self-oscillation, which is a fairly common problem I've seen with PID -- especially where there is a significant time delay in the loop. One of the cheaper ways to handle that is to simply shorten the delay. Even a brain-dead PID controller can do a credible job on controlling a process where the loop time is shorter and repeatable.

You mention having created a solution with an ATmega that works already, but that your company doesn't want to use it. Instead preferring to buy something on the outside. Why? Many would very much like to be in control of something like this. You state the desire for 3rd party suppliers of PID boxes and a lack of worrying about supply problems in the future, etc. But isn't that exactly what you get when you make it, yourself?

Is the real reason because they don't believe you've really got all the "quirks" worked out and they don't want to take risks that there will be a lot more time needed to shake out what you've already done?

Small or first-time suppliers will be "risky" from that point of view, I suppose. So which larger manufacturers have you already looked at, what devices, and why aren't they suitable? That would also help a lot, for whomever tries to answer you effectively.

Tim Wescott may have a great deal to add to all this, but frankly I'm in need of more information before having any idea what to recommend, technically.

Jon

Up to here it sounds like that is feasible with programmable logic controllers (PLC). Allen-Bradley, Danaher, Omron, Siemens and many others. But it depends how fast your loop needs to be.

Why? Put an LCD and buttons on them, have them produced, use as many as needed for your purposes and sell the rest like hot cakes, make oodles of money. Ask your employer for a 2-3% revenue sharing incentive, buy a tropical island, a LearJet, a few crates of margarita mix, then retire.

PLC can do all that if your loop timing isn't super fast. But they cost a pretty penny and usually every ever so little extra such as LCD, ADC/DAC or keypad costs extra. Oh, you want a steering wheel with that car? That's be another $100. Maybe you can find a budget version that has at least a tiny LCD and 4-5 buttons.

Boxes geared more towards PID:

--
Regards, Joerg

http://www.analogconsultants.com/

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That's exactly what we have:

http:linnix.com/pid.jpg

LCD, LM358 A2D, 2 or 4 buttons, 10 pins external interface.

We get several hundred hertz closed-loop responses.

uts

We did so too. But AVRs are too expensive.

We can customize it for the OP.

We sell them for less than $10. It would need huge qty to afford the island, jet, etc.

Does it have a DAC as well so you can control the analog plant input?

That is sufficient for many if not most process control jobs.

Now you've piqued my interest. Is there a datasheet of the unit and maybe a photo with housing? Maybe a little more in focus, the one in the link looks like it was taken after a meeting with Jose Cuervo ;-)

--
Regards, Joerg

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Yes, half of the LM358 is unused. It can be customized as another A2D or an external integrator for better responds.

nputs

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Not yet, but we have discussed many issues here in CAE or SEC

Most recently, the supply voltage issue. It is now happily running a

4.2V LDO (better) or LM317 (cheaper) regulator for the op amp and sensor, minus a BAV99 drop for the 16K OTP ASIC. The LCD is nice and clear at 3.6V.

But your main page --

-- announces "Hi there, we don't want you as a customer".

Or at least it only wants customers who are willing to log in blind to an unknown site.

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http://www.wescottdesign.com

Cynicism, mostly.

Outsourcing wisdom says that you do your 'core competencies' and you farm out the rest. As an employee, I saw innumerable times when management farmed out stuff to 'experts' who completely failed to understand the needs of the company, failed miserably at what they signed up to do, and ended up doing nothing but costing money and causing grief. (In fact, I'm getting paid good money now to fix up one of those for a client). As a consultant, I see over and over again when an in-house design effort fails, gets pushed far too far, and management only panics and calls me in after it's too late to do much but wrap bandages in an intelligent and thoughtful manner.

I only know of two dedicated embedded PID controllers, including the linnix one. The one example of this that I've worked with was pretty pedestrian; in many cases you could just read my PID article and roll your own -- anything you lost in PID expertise you'd gain back with an intimate knowledge of how your own system.

I think, frankly, that the reason you don't see more is because it _is_ so easy to tuck a PID controller into the corner of a larger general- purpose embedded controller -- so why go buy one special?

It'd be interesting to see what linnix has to offer, if the site would cough up more than a few lousy pictures.

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http://www.wescottdesign.com

[...]

The market would be companies like Jamie's. For whatever reason, liabitity, procurement, whatever, they don't want to roll their own. Other times there just isn't anyone who can program a uC. But most of all people want this:

Something that drops in, does not have potmeters that can get screwed up, can be pre-programmed and shipped, and has mounting screw holes as well as screw terminals. For high rollers maybe even a clickable DIN rail version.

He said they'll have discussions, probably how much and when to release info. Eagerly awaiting that ...

--
Regards, Joerg

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Actually, it says we are too busy to make fancy web pages. The main page log into our email system only. Our customers know were to look for subfolders. We will update more for this later.

Unlike Flash, OTP development cost is very high. I don't think many people want to deal with it. But volume production cost is much lower. The entire BOM for this board is $2 to $3, same as the 10K price for the Flash based LCD AVR chip alone.

Give me more time, please.

Right now, I am busy trying to solve the external integrator problem. Our customer needs better closed-loop response with hardware integrator. At the end of a cycle, I need a high resistant switch to discharge the capacitor. The MOSFET I tried did not isolate well enough. Mechanical relay works, but size is a problem. I need a SOT-23-5 sized semiconductor relay. Any suggestions?

We have high end process loop controllers how ever, these are intended for user operation and is not what we're looking for..

using a process controller configured out side it's normal use does not work well or not at all and most of them I've seen do not provide a unipolar/bipolar outputs with differential inputs with a ref source.

The keyboard interface we're looking for is a very simply one. Just a M, UP/DOWN pin switches with mini LCD screen edged soldered..

These units are intended for one time calibration and to be mounted internally.

We have a variety of other devices that are DIN Rail mounted that employs their own little mini LCD screen with a minimum set of buttons to program them.

It's just that I can not find A PID unit in such a configuration for DIN rail mounting.

PLC's are way expensive for this simple application.

But I'll take your suggestions of manufacturing the existing units we have made in house as a solution for 200 or so to be made. We have already looked into Display supported Uc's and the use of simple serial LCD displays.

You mean something like this?

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We have MODE, UP, DOWN and SAVE (confirm). The LCD has labels M1,M2,...M5. It is a 12x4=3D48 segments glass with 0.1" pitch dual row pins. See picture at:

This LCD is standard -20C to 50C operating and -40C to 60C storage temperature. But if you need to store your equipment in the arctic,

-45C to 70C operating and -70C to 80C storage is available.

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Making an adapter should not be a problem.

Serial LCDs are several times more expensive than segmented LCD. I repeat, our BOM cost is $2 to $3, depends on batch volume. If you are ready to talk, drop me a email at "linnix live com". Replace and with symbols.

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Maybe a low charge injection analog sw similar to what has been used for video switching?

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Is this statement reasonably close; "Basically what your management seems to want is a standard product embedded plc on a pwb." If so use "embedded plc" with a search engine and beware the 50,000 others who are trying to get between you and the hundred or so actual manufacturers.

[...]

Ok, time's up now.

Just kidding ...

What's the leakage requirement? In many older analyzers this was done with small JFETs. But if you only have +3V or something like this it'll be more of a challenge.

--
Regards, Joerg

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d e

It would be approx. 10K R and 0.01uF C with 3.5V charging and discharging. If I connect a 2N7002 across the C, it wouldn't charge at all. I guess the MOSEFT off-state leakage is larger than the 10K R.

That's initially 350uA. A lot. The 2N7002 sits at 1uA for off. Maybe too much flux or something?

But the 2N7002 is too fat for this and at higher temps leakage really hits. These are usually better for this app although not spec'f at 0V:

Anything from the SD-sries would probably be too expensive for your project.

--
Regards, Joerg

http://www.analogconsultants.com/

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I know it doesn't make sense. I wired up a test circuit with the gate grounded. Just hooking up Drain and Source stops the capacitor from charging.

OK, thanks. I'll try this, if I can get a sample.

ct.

Supply voltages, bias conditions,...? Is your output bipolar WRT to minus input? Is your 7002 still OK? (ESD)

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Thanks,
Fred.