Good price for a prebuilt PID controller?

[MikeS]

Hi All.

I've seen several threads here about building PID controllers for keeping lead pots at the proper temp. My ability to do anything with electrical devices, or wiring in general is less than zero! The other day I saw a guy on eBay selling PID controllers, and in looking at his stuff he sells a complete unit that is plug and play (which is about my level of electrical ability!) PID controller that looks similiar to some I've seen here. It has the PID mounted on the front, along with a fuse, and on the back is a plug to plug in the controlled device, a place to plug in the electric cord going to the wall, and the thermocouple comes out the back as well. He's selling it for cooking, but I asked him if it could do what I want, and he said yes it could, he would just have to change the thermocouple. He's selling the complete unit for $119.00 + 5.00 for the different thermocouple.

So my question is: Is a PID controller already put together worth that price? I realize I could buy all the components for probably about $50.00 or so, so he's getting roughly another $75.00 for his labor putting it together, which I think is a fair price, after all, nobody wants to work for free. Here's the link to the unit he's selling, anyone that's good with this stuff, please let me know if you think it's put together well, and so is worth his asking price.

http://www.ebay.com/itm/110752055197?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_2770wt_884

Thanks everyone for taking the time to look at this, and please let me know what you think.

[Lee W]

It looks like it came from here:

http://thermomart.com/index.php?route=product/product&product_id=72

I would say it is a good price since it is in a box and most likely tested. The probe is only good to 752 F, so be careful of that.

[Casting Timmy]

I think the price on the unit is a fair price.

[thehouseproduct]

http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=161

[scrapcan]

also remember that you having international shipping on the ebay item as the seller is in Ontario Canada.

[uscra112]

When I was building environmentally controlled chambers for precision measuring machines we used a high quality unit made by Watlow. It wasn't very expensive. If I ever see a need for a PID for my pot, (which I don't), I'd go directly to Watlow. These were totally reliable - hundreds of installations ran 24/7/365 in auto plants, where a breakdown is a capital offense. What you would get from a cheap eBay purchase is anybody's guess. Buy cheap, buy twice.

[Mike W1]

If I were you I'd check out the guy that has an ad in The Fouling Shot. I don't have one myself but his are supposed to be good units.

[Frozone]

I had planned to produce a few for sale.
Problem was, by the time I payed shipping on all the components, I couldn't get the price down to 'reasonable' levels.
I could build em for ~$100 but shipping drove the price up to $150+.

[Sonnypie]

I do not like fleaBay. But lots of other folks do...
I'm always more inclined to deal with what I feel are "Brick and Mortar" stores.
What TheHouseProduct has linked would be, in my electrical background opinion, a very good choice.
You poke in what you want, it takes you there, and you go WOW! THIS is cool! (In a hot way)
But add the Type K thermocouple (http://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=22) and you are at $200.

Now... I have to ask myself, "Self, are you really sure you want a $200 controler for your $63 Lee furnace?"
>
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Nnnaaawwww.... :holysheep

[Dutchie]

Mike , Hi from the other side of the world.

As an electronic engi I'd say its a fair bill.

@sonnypie
If one wants to perfectly cast his boolits at any level in the lee furnace and to really control the temp >

I would ask my self the same question . . . . . . . . . . yep!.

But , nobody can look in otherones wallet, priorities priorities. . . . . . .

[Sonnypie]

And then you pour your "perfect" temperature lead into an uncontrolled mold.... [smilie=b:

:wink:[smilie=1:

BTW... I was one of the guys who fixed what engineers designed so it would actually work. :drinks:

But that's another time, that's another place, that's a different life.

[Frozone]

And then you pour your "perfect" temperature lead into an uncontrolled mold....

I begin to doubt you truly know how to cast. The mold temp is controlled by the initial lead temp and speed you cast at.

[MikeS]

Well, I guess I'm going to play guinea pig, as I just bought one of the controllers from the Canadian seller on eBay. With shipping, and the changed thermocouple it came out to right around $160.

To answer the question of why spend $160 to control a $63.00 Lee furnace, it's simple. First off, the controller isn't tied to the Lee pot, so I could use it in any other pot I get in the future, and by adding the PID controller it makes the temp control of the Lee pot better than many $300 pots, and just because I got one part of the setup cheaply doesn't mean I need to stay with everything else cheap, if I used that logic I would cast with nothing but Lee 2 cavity moulds, and that's something I do not do. And as for why bother keeping the temp regulated so closely, it's simple, it adds another level of uniformity to the casting process. Try casting some boolits at 600 degrees, then crank the pot up to 700 degrees and cast some more (of the same boolit), then crank it up to 800 degrees and cast yet more. Once they've cooled down, weigh and measure the boolits from each lot, and you will see a difference between their weights & sizes. Having the ability to keep the lead in the pot at a set temp, and know that I can repeat that same temp any time I want to is worth the money to me.

The Auberins units look nice, and if I hadn't already bought the one I just did, I might have bought one of them. I think the one I got might have a small advantage in that the case looks larger, with the components more spread out (I'm assuming this last point as I haven't seen the insides of any of the Auberins units), so chances are it will stay cooler, but I could be wrong, sometimes it's hard to get a good idea of size from photos.

[Colorado4wheel]

What is the upgraded temp sensor for? All the other setup I have seen are around $80?

[MikeS]

The original thermocouple that he supplies with this unit only goes up to around 750F, and the upgraded one goes up to around 1250F. The one's you've seen around $80.00 is that for a kit, or a fully assembled ready to use unit?

[bwgdog]

Mike-Please keep us updated on this project!

[lts70]

I wonder if we did a group buy if it would make it more realistic for one of our PID experts to save money on supplies & shipping and crank out a bunch of these to sale here on the board? Or even contact a company that already produces them for sale and see if they would give us a group discount.

[bwgdog]

Have that thought also-Frozone-Would you have any input/interest? tia barry

[MikeS]

I will let y'all know how the PID controller I bought works. Too see what his answer would be, I asked the guy if I should keep the pot plugged into the controller from cold till it's up to temp, or if I should plug the controller in once the pot was almost up to temp, and his answer was that while I could keep it plugged in from cold, the controller's life would be greatly extended if I plugged it in once the lead was up to temp. Being the lazy person that I am, I think I'm going to attempt a simple project, and build a box with a switch on it, one way the pot would be getting power directly from the wall, the other way it would be getting power thru the controller. This way I could flip the switch and get the pot up to temp, then with a simple flip of the switch I could have power coming from the controller. Maybe I'm being overly cautious, but I don't like plugging in and unplugging a pot full of hot lead. While chances are it couldn't do anything bad, but there's always the chance that Murphy will show up, and the cord will cause the pot to spill some lead, and of course it would be on ME!

I think I might ask him (the eBay seller) if he would give a quantity discount, and if so, how much. I showed the eBay listing to a friend of mine who's a lot more electronically savvy than I am, and he said it was actually a pretty good price, considering that the kit was around $75.00 IIRC and his finished unit is $125.00 so for $50.00 he's supplying an enclosure, cutting out all the openings in that enclosure, and then installing all the parts into it. If he (my friend) was to do that, considering that he doesn't have a machine shop at his disposal he said it would probably take about 2 hours to make all the proper openings in the case, then another half an hour to actually wire it all together, add another half an hour to check everything, that makes 3 hours assembly time, and he said that the case shown in the eBay listing is one that probably costs around $20.00, so he would be working for about $10.00 per hour which is not a lot of money these days! Of course the seller probably HAS a machine shop available to him, or at least has the proper tools to make all the cutouts, which would make it take much shorter to do, so it's probably taking him an hour or so to build it. And I'm sure he's buying the enclosures in bulk, and so getting them at a good price too. Still a good price all things considered. Now to see if the unit I get looks as nicely wired as the one in the auction listing!

[kitsap]

I will let y'all know how the PID controller I bought works. Too see what his answer would be, I asked the guy if I should keep the pot plugged into the controller from cold till it's up to temp, or if I should plug the controller in once the pot was almost up to temp, and his answer was that while I could keep it plugged in from cold, the controller's life would be greatly extended if I plugged it in once the lead was up to temp. Being the lazy person that I am, I think I'm going to attempt a simple project, and build a box with a switch on it, one way the pot would be getting power directly from the wall, the other way it would be getting power thru the controller. This way I could flip the switch and get the pot up to temp, then with a simple flip of the switch I could have power coming from the controller. Maybe I'm being overly cautious, but I don't like plugging in and unplugging a pot full of hot lead. While chances are it couldn't do anything bad, but there's always the chance that Murphy will show up, and the cord will cause the pot to spill some lead, and of course it would be on ME!

MikeS,

In my opinion your caution is well founded and the answer from the builder about extending the life of the controller was solid. I built both a pot and controller. The controller has a double throw switch that allows me to power the pot either direct from the AC source (input to the SS relay) or regulated via the controller (output from the SS relay). With a cold pot I have the switch in the direct position and let the lead come up to within 50-75 degrees of temperature before I switch to regulated. Not something you want to power on and then walk away from.

DougF

http://i1139.photobucket.com/albums/n546/kitsap1/Lead%20Pot%20and%20Controller/LP-3a.jpg

[Sonnypie]

I begin to doubt you truly know how to cast. The mold temp is controlled by the initial lead temp and speed you cast at.

Opinions are like A__holes. Everybody has one. ;-)
I can't see spending that kind of money when I can do every bit as well as I am currently running. I measure my casting in pounds and sacks of ready boolits. But hey, in your opinion I don't know how to cast.... right...

BTW, I use to work on, test, and repair far more sophisticated controls. And still could. I could build from scratch, and have.
But I can not see the worth in it. [smilie=1:
When it fails, you fellers can always buy another one. But remember, your cost of "perfect" temperature control goes up exponentially.
Enjoy. :wink:

"Hey John, how do I plug this into my turkey fryer?" :???:

I bet my Great, Great, Great, Great Uncle is LOL. He used an iron pot over a camp fire during the civil war. Now that was temperature control.... :lol:

Do enjoy your toys. :violin:

[Sonnypie]

I will let y'all know how the PID controller I bought works. Too see what his answer would be, I asked the guy if I should keep the pot plugged into the controller from cold till it's up to temp, or if I should plug the controller in once the pot was almost up to temp, and his answer was that while I could keep it plugged in from cold, the controller's life would be greatly extended if I plugged it in once the lead was up to temp. Being the lazy person that I am, I think I'm going to attempt a simple project, and build a box with a switch on it, one way the pot would be getting power directly from the wall, the other way it would be getting power thru the controller. This way I could flip the switch and get the pot up to temp, then with a simple flip of the switch I could have power coming from the controller. Maybe I'm being overly cautious, but I don't like plugging in and unplugging a pot full of hot lead. While chances are it couldn't do anything bad, but there's always the chance that Murphy will show up, and the cord will cause the pot to spill some lead, and of course it would be on ME!

I think I might ask him (the eBay seller) if he would give a quantity discount, and if so, how much. I showed the eBay listing to a friend of mine who's a lot more electronically savvy than I am, and he said it was actually a pretty good price, considering that the kit was around $75.00 IIRC and his finished unit is $125.00 so for $50.00 he's supplying an enclosure, cutting out all the openings in that enclosure, and then installing all the parts into it. If he (my friend) was to do that, considering that he doesn't have a machine shop at his disposal he said it would probably take about 2 hours to make all the proper openings in the case, then another half an hour to actually wire it all together, add another half an hour to check everything, that makes 3 hours assembly time, and he said that the case shown in the eBay listing is one that probably costs around $20.00, so he would be working for about $10.00 per hour which is not a lot of money these days! Of course the seller probably HAS a machine shop available to him, or at least has the proper tools to make all the cutouts, which would make it take much shorter to do, so it's probably taking him an hour or so to build it. And I'm sure he's buying the enclosures in bulk, and so getting them at a good price too. Still a good price all things considered. Now to see if the unit I get looks as nicely wired as the one in the auction listing!

MikeS,
He probably works in a shop that builds panels and control cabinets. Therefore having access to the punches, Unibits, and tools of the trade.
Electronics have to be designed around the perimeters of the control.
The inrush current would be of major concern for a 700 watt purely Resistance load like a furnace element.
(The inrush current on a conventional 100 watt light bulb is 17+ AMPS for several milliseconds. Then the element is white hot and drops back to the nominal 100 watts.)
I think your plan of pre-heating, then switching in the control is a good one. That way the solid-state switch is not working full-bore to bring the mass up to perimeters. Heat is the #1 enemy of electronics.
If you could put the thermocouple in a well (http://www.omega.com/ppt/pptsc.asp?ref=SERIES_385A_260A&ttID=SERIES_385A_260A&Nav=) I believe it would last longer too. It would certainly be better protected.
That is what we did in Industrial controls for our equipment and processes monitoring.

You might consider adding a well to your set-up as well, DougF. You could heliarc the well into your furnace pot. Very nice build, by the way. It appears you are a dipper?

What about a ramped zero crossing switching to transfer the control from raw(Pre-heat) to PID?
Do you guys know if these are Triac or SCR drives (http://en.wikipedia.org/wiki/TRIAC)?
Doug, are you switching just the output of your PID? Or turning the PID on and the bypass off with your panel switch?
Just curious....

[MikeS]

Doug: I'm curious, as you're building the pot as well, why did you go with the probe (thermocouple) that you did, rather than one permanently attached to the pot? As I've said before, I'm retarded when it comes to electronics, or electrical work, so could you show me a simplified schematic (by simplified I mean don't use any terms I might not understand!) of how you wired in the switch to switch between unregulated heat (power), and regulated heat? I was originally thinking of doing it external to the PID controller I bought, but have been thinking that would mean yet another box to find room for on my casting bench, so have been thinking of adding the switch internally. I can handle drilling a hole in the box for the switch, and hopefully the wiring involved as well.

Sonny: You didn't complete the line about opinions, it should be "Opinions are like A#$holes, everyone has one, and some stink worse than others" :) (BTW, my correction of the quote has nothing to do with the person you were telling that to, I don't even recall right now who it was, or what was said) As for putting the probe in a well, I didn't even know that such things existed until just now! Would putting the probe into a well like the one shown on your link, would that affect the probe's reading at all?

Another question I have is regarding the unit of measure. The one I'm getting reads in C rather than F, would that affect the controller's accuracy? I mean one degree C is a much larger jump than one degree F would be.

[kitsap]

Doug: I'm curious, as you're building the pot as well, why did you go with the probe (thermocouple) that you did, rather than one permanently attached to the pot? As I've said before, I'm retarded when it comes to electronics, or electrical work, so could you show me a simplified schematic (by simplified I mean don't use any terms I might not understand!) of how you wired in the switch to switch between unregulated heat (power), and regulated heat? I was originally thinking of doing it external to the PID controller I bought, but have been thinking that would mean yet another box to find room for on my casting bench, so have been thinking of adding the switch internally. I can handle drilling a hole in the box for the switch, and hopefully the wiring involved as well.

Another question I have is regarding the unit of measure. The one I'm getting reads in C rather than F, would that affect the controller's accuracy? I mean one degree C is a much larger jump than one degree F would be.

MikeS,

I have/had the option to put a thermocouple on the surface of the external wall of the pot or to drill and tap a hole for a threaded thermocouple. I chose the free standing probe because I wanted to know the temperature of the lead at various locations within the pot. I did not choose the surface probe because I wanted to regulate the temperature of the lead and not the temperature of the wall of the pot. The wall of the pot is 1/4 inch thick stainless steel. The band heater I used fully covered the outside circumference of the pipe. The only location option for a threaded thermocouple was on the bottom and I just didn't like it there.

In the next few days will get something drawn up for hooking up the switch. I would also recommend a pilot light so it is easy to verify when power to the heating element is applied.

DougF

[kitsap]

Doug: I'm curious, as you're building the pot as well, why did you go with the probe (thermocouple) that you did, rather than one permanently attached to the pot? As I've said before, I'm retarded when it comes to electronics, or electrical work, so could you show me a simplified schematic (by simplified I mean don't use any terms I might not understand!) of how you wired in the switch to switch between unregulated heat (power), and regulated heat? I was originally thinking of doing it external to the PID controller I bought, but have been thinking that would mean yet another box to find room for on my casting bench, so have been thinking of adding the switch internally. I can handle drilling a hole in the box for the switch, and hopefully the wiring involved as well.

Another question I have is regarding the unit of measure. The one I'm getting reads in C rather than F, would that affect the controller's accuracy? I mean one degree C is a much larger jump than one degree F would be.

MikeS,

Here is a schematic for hooking up the switch and optional pilot light.

PIDSwitch-Model.jpg (http://i1139.photobucket.com/albums/n546/kitsap1/Lead%20Pot%20and%20Controller/PIDSwitch-Model.jpg)

There should be no accuracy difference between the degrees C and degrees F measurements. When you measure a foot, it is the same distance whether it is described as 12 inches or one foot. Just different units of measurement.

DougF

[MikeS]

Doug:

Yes, but when using feet to measure something, and assuming there's no decimal points involved, 144" is 12', and 149" would still be considered 12', until a point when it would become 13'.

I got the controller, and it seems to work pretty good. I've been casting at 330C which is 624F (or is it 625, I'm doing the conversion from memory), and the controller seems to hold it between 329 & 332.

The guy that made it has like 5 more that if folks here were interested in, I can buy them for $150.00 each + shipping (the 150 includes shipping from Canada to me). I told him I would ask here, and see if there was any interest, and let him know. That also includes the higher rated thermocouple (which has a steel braided cord on it to protect the wires should some lead drip on it). I don't know if that's a good price or not, but that's the same as I paid for my unit with the shipping. Anyway, if anyone is interested, let me know, and I'll let him know. Just to be on the 'safe' side, when I mentioned this forum, I didn't mention that it was a boolit casting forum, only a lead casting forum, as I've found that some folks freak at the idea of making boolits! (stupid liberals!) I didn't want to have him freak on me, so I left off the part about boolits, I don't know if that was being over protective on my part or not.

[Suo Gan]

So my question is: Is a PID controller already put together worth that price?

No, not to me. I might try one for $25. Until then I can get along just fine without one.

[rbertalotto]

That way the solid-state switch is not working full-bore to bring the mass up to perimeters.

Huh? I thought the relay is either open or closed. When it is closed, and held there until the pot is at temperature, the only issue for longevity might be the circuitry holding the relay closed. But once it is closed isn't it simply a through feed? And isn't the PID simply switching the relay open and closed? And lord knows a switch such as this can go through MANY more duty cycles than we might put it through in a bunch of casting sessions...........

[Lee W]

As long as the SSR has a heat sink and is operating at it's ratings or less, it should last forever. According to this app sheet, about 2100 years.

"When SSRs are used within the published specifications, MTBF can exceed 19 million hours."

www.clare.com/home/pdfs.nsf/www/an-145.pdf/$file/an-145.pdf

Or read this FAQ suggesting greater than 228 years .

http://www.crydom.com/en/Tech/FAQs.shtml#p08

[MikeS]

I also got thrown by the question of using the PID/SSR to bring the lead up to temp, or if I should plug the pot directly into the wall outlet, and switch over to PID when the temp is close to the set temp. I asked the seller which way to use it, and he said I could use it either way, but said using wall jack power to provide the initial heat up wouldn't be bad. I have a friend that's into electronics, and stuff like that, and I asked him too, and he also said it would keep the relay cooler to preheat the lead, as he said due to the AC current it would be switching on/off 60 times a second during the warm up period. Once I got the actual unit, and showed my friend the wiring diagram he changed his mind. He said that due to the design using an SSR rather than a regular relay (what he thought it was using initially) that it wouldn't hurt the SSR at all to just let the pot warm up while being plugged into the PID controller. When I turn on the unit I hear a click, and I don't hear it again until the pot is very close to the set temp, then I can hear it cycle on/off.

I really like using the unit, as now I know more precisely what the temp is of the pot, and even more important, unless adding ingots, the pot will stay at the desired temp. My Lee pot would hold a temp fairly well while I'm actually casting with it, but if I leave it alone for a while (without throwing in sprues on a regular basis) the pot will jump up more than 300 degrees in about 30 minutes. Now using the PID controller I've left the pot sit by itself (while inside eating dinner) for about 45 minutes, and when I got back to it, the set temp was still the temp it actually was!

Well, as nobody has expressed any interest in buying one of this guy's pre-constructed PID heat controllers I will let him know not to hold them for me anymore. I would like to thank everyone that posted their thoughts about this controller here!

[Sonnypie]

Sonny: You didn't complete the line about opinions, it should be "Opinions are like A#$holes, everyone has one, and some stink worse than others" :) (BTW, my correction of the quote has nothing to do with the person you were telling that to, I don't even recall right now who it was, or what was said) As for putting the probe in a well, I didn't even know that such things existed until just now! Would putting the probe into a well like the one shown on your link, would that affect the probe's reading at all?

Another question I have is regarding the unit of measure. The one I'm getting reads in C rather than F, would that affect the controller's accuracy? I mean one degree C is a much larger jump than one degree F would be.

MikeS,
Sorry. I missed this and am just getting back to it.
Putting your thermocouple in a well protects it from direct contact with what it is reading. Since the well heats and cools along with the material being monitored, there is very little reluctance for the probe to error on.
Also it keeps the thermocouple from getting crud caked on it. Especially in the environment of metal smelting.

*C is a wider span than *F.
100*C = 212*F
725*F = 385*C Fahrenheit to Celsius Converter (http://www.wbuf.noaa.gov/tempfc.htm)

It should not be of much concern for alloy smelting for casting. It will be plenty accurate. As long as the builder has done his job and used quality components in the controller itself.
Therein lies the catch. Anytime we designed and built different control schemes, you need to be in the middle or lower end of the process.

In simpler terms, a gauge works best if if it mid span, like a 200 PSI gauge for a 100 PSI system.

So you wouldn't want to operate a 750 degree control at peak. Better to have your control able to range higher, and control lower.
So what that means is not a 750 degree control system for lead smelting.
But rather a 1500, or 2000 degree control system operating (loafing along) at 725-750 degrees.

Error is based on full scale. So 2%, or 5% of full scale is a bigger number with a 750 degree control system.
But for a 2000 degree system operating at 750 degrees, the error is much less. And the control better. Make sense?

Getting back to A_ _holes....
My biggest concern is these entrepreneurial types taking frying components and telling folks they will work for metal smelting.
They might, for a while. Long enough for the check to clear...
Then you are bent over a barrel. :-( And they are gone.

That is why I prefer to do business with brick and mortar businesses.

I spent 42 years in Industrial and Utility Electrical control and maintenance. I'm one of the guys who made it work, and kept it working. I know what it takes, how to get it, and how to keep it working.
And I still can't see me putting a $200 control scheme on my $67 lee Pro 4 - 20 pot.
YMMV, with all due respect.

[JIMinPHX]

"Hey John, how do I plug this into my turkey fryer?" :???:


With an E to P valve & a calibrated orifice.

[JIMinPHX]

I will let y'all know how the PID controller I bought works. Too see what his answer would be, I asked the guy if I should keep the pot plugged into the controller from cold till it's up to temp, or if I should plug the controller in once the pot was almost up to temp, and his answer was that while I could keep it plugged in from cold, the controller's life would be greatly extended if I plugged it in once the lead was up to temp. Being the lazy person that I am, I think I'm going to attempt a simple project, and build a box with a switch on it, one way the pot would be getting power directly from the wall, the other way it would be getting power thru the controller. This way I could flip the switch and get the pot up to temp, then with a simple flip of the switch I could have power coming from the controller. Maybe I'm being overly cautious, but I don't like plugging in and unplugging a pot full of hot lead.

I think that's a good move. I probably would have done the exact same thing.

The part of the controller that gets it's butt kicked from a cold start up is the power handling device, which is probably an SSR (solid state relay). You can just go out & get a massive huge SSR that will take the beating, but that gets expensive.

Ohmic heating loads have a calculated inrush current of 10 times the rated steady state current & that is what you would want to scale your cold start current rating to when selecting an SSR. The inrush of an ohmic heating load is even more severe than the normal inrush from an inductive motor, that is calculated at 6 x full load amps. The switch is a very cost effective alternative to an expensive SSR.

[JIMinPHX]

Another question I have is regarding the unit of measure. The one I'm getting reads in C rather than F, would that affect the controller's accuracy? I mean one degree C is a much larger jump than one degree F would be.

Accuracy is the same. Output display scaling is just different. Many controllers can switch from one to the other.

[felix]

The installation of a make-before-break switch, and/or a logically controlled switch that will not permit a break until the lead/pot is up and over the targeted temp, or, for the best solution, a soft-start control immediately after the PID controller. Of course, the latter would be my solution for the total gadget longevity, but at what cost? Prohibitive for something other than professional use. The occasional caster doesn't need any additional cost provided he casts a year's worth or so boolits per outing. ... felix

[JIMinPHX]

This thread may also be of interest - http://castboolits.gunloads.com/showthread.php?t=22624

[felix]

Yep, prolly this unit I would use. Talk about overkill. But, it will make everything last longer than it should.

http://www.newark.com/jsp/search/productdetail.jsp?SKU=13N4509&CMP=AFC-GB100000001

... felix

[flashhole]

Interesting thread - just for clarification (degrees C X 1.8) + 32 = degrees F

Example - boiling point of water 100 C or 212 F

(100C X 1.8) + 32 = degrees F

180 C + 32 = 212 F

[JIMinPHX]

Felix,
you can find much better prices on SSRs these days - http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Solid_State_Relays/Panel_Mount_Relays,_Hockey_Puck_Style,10A_-_75A_%28AD-SSR6_Series%29/AD-SSR650-AC-280A

[onesonek]

Well, I guess I'm going to play guinea pig, as I just bought one of the controllers from the Canadian seller on eBay. With shipping, and the changed thermocouple it came out to right around $160.

To answer the question of why spend $160 to control a $63.00 Lee furnace, it's simple. First off, the controller isn't tied to the Lee pot, so I could use it in any other pot I get in the future, and by adding the PID controller it makes the temp control of the Lee pot better than many $300 pots, and just because I got one part of the setup cheaply doesn't mean I need to stay with everything else cheap, if I used that logic I would cast with nothing but Lee 2 cavity moulds, and that's something I do not do. And as for why bother keeping the temp regulated so closely, it's simple, it adds another level of uniformity to the casting process. Try casting some boolits at 600 degrees, then crank the pot up to 700 degrees and cast some more (of the same boolit), then crank it up to 800 degrees and cast yet more. Once they've cooled down, weigh and measure the boolits from each lot, and you will see a difference between their weights & sizes. Having the ability to keep the lead in the pot at a set temp, and know that I can repeat that same temp any time I want to is worth the money to me.

The Auberins units look nice, and if I hadn't already bought the one I just did, I might have bought one of them. I think the one I got might have a small advantage in that the case looks larger, with the components more spread out (I'm assuming this last point as I haven't seen the insides of any of the Auberins units), so chances are it will stay cooler, but I could be wrong, sometimes it's hard to get a good idea of size from photos.

My thoughts are, anything one wishes or can do in the aid of consistency, can be a good thing. As for need and cost, that is more a personal matter. Hope it works out to your expectations Mike.

[Mal Paso]

I think that's a good move. I probably would have done the exact same thing.

The part of the controller that gets it's butt kicked from a cold start up is the power handling device, which is probably an SSR (solid state relay). You can just go out & get a massive huge SSR that will take the beating, but that gets expensive.

Ohmic heating loads have a calculated inrush current of 10 times the rated steady state current & that is what you would want to scale your cold start current rating to when selecting an SSR. The inrush of an ohmic heating load is even more severe than the normal inrush from an inductive motor, that is calculated at 6 x full load amps. The switch is a very cost effective alternative to an expensive SSR.

As a practical mater the Auber's 25 Amp SS Relay handles the 6 Amp Lee Pot just fine. There is no switching until the temperature gets close to setpoint. My relay is attached to the back of it's cabinet and has never been warm. Solid State devices handle short heavy loads quite well, it's the heat from sustained heavy loads that will kill them. Your theory is good but it takes time for the silicon to heat up too and as long as it doesn't overheat all is good.

[JIMinPHX]

Solid State devices handle short heavy loads quite well, it's the heat from sustained heavy loads that will kill them. Your theory is good but it takes time for the silicon to heat up too and as long as it doesn't overheat all is good.

My experience tells a slightly different story. From what I've seen, a sustained heavy load that causes the device to get very hot will cause an immediate failure as you describe, but repeated short duration bursts of current will have a cumulative detrimental effect, sort of like taking a swing at a big tree with a hand ax. One or two swings of the ax will not bring the tree down, but if you keep doing it, eventually the tree gets weak & does come down.

The inside of a semiconductor power handling device is basically a big matrix of P-N junctions. To oversimplify things a little bit, the more of the P-N junctions you put in series, the higher the voltage rating you get & the more of the P-N junctions you put in parallel, the higher the amperage rating you get. Each instantaneous overload causes the loss of a small percentage of the P-N junctions & shifts increased load to the remaining junctions.

I saw this best demonstrated in the field by elevator mechanics in NYC. When they set the deceleration rate on a variable frequency drive to 0.3 seconds or less, the peek current would generally spike above the maximum for a short period of time each time the elevator moved & the drive would generally fail within several months. When the deceleration time was programmed to 2 seconds or more, the peek current would be far lower & the drive was usually good for 10 years or more. At that time, the drive usually failed from blown filter caps & not a bad power switching device.

Mal,
In your example, the short term current spikes may have been small enough as to not do physical damage or your previous experiences may have had other mitigating factors that overcame the effects that I described. The effects do exist though.

[Mal Paso]

I work with off grid inverters. The better ones can put out 4 times rated power for short periods to start motors and run for years, 15 and counting in some cases. The best examples are houses built from solar power. The system runs all the tools from compressors to overloaded saws building the house and goes on to power the house indefinitely 24/7.

You might be right. I've only run 150# of lead through it. It's a $15 part so I'll run the :takinWiz: out of it and will report promptly when it fails. I have a back up pot I should have a backup controller too. I wouldn't worry about backups in if I was in Phoenix but Casting Weather here is when the mud's too deep to go anywhere.

The PID kicks the value of my Lee pot up a couple hundred bucks. I'm running a lower temperature, 730, with a single brass 4c 250g mold at 9 boolits a minute. 5 to 10 seconds under a sprue plate cooling fan. Mold stays clean, best boolits yet.

[JIMinPHX]

You may have been working with inverters that were spec'd more conservatively in those solar systems. They may have had more fluff room built into them at the design stage.

The equipment in the elevators that I saw in NYC was built to be what it needed to be & not a whole lot more. The safety systems in those elevators were on the mechanical end, not the electrical size.

Time will tell though.

One of the key safety devices in a elevator is a set of counter weights. In the very old days, they were made out of lead. Lead was banned long ago because it was not safe to rely upon in the event of fire. Those weights have been made out of mostly ferrous metals for some time now, but if you ever see an elevator getting ripped out of an old building, it's worth taking a look to see what kind of weights are getting scrapped out. The elevator guys have absolutely no use for the lead ones any more. The main bearings that are used in the overhead shaft systems are often made from Babbitt too. That stuff is like lineotype on steroids.

[MikeS]

Jim:

Off topic, but you reminded me of the building in NYC where our business was for years. It had a freight elevator that had a cable that ran the entire height of the building as it's control. To make the elevator go up the operator would pull down on the cable, and then to stop it he would grab the moving cable, (actually the cable was stationary, it was the elevator car that was moving!) and to go down he would again pull up on the cable. the elevator operator had a rag by the control, but rarely used it, as his hand was so calloused from running the elevator for years that he didn't need the rag, it was only there for the relief operators! The actual switch was located in the basement of the building, the cable just remotely operated the switch. Our business had the ground floor and the basement, and the elevator didn't go all the way down in the basement, the elevator usually stopped about 8 - 10" from the floor, but if he took the elevator up a few floors first, and let it come down, and stop via the limit switches built in he could get it to go lower, so there was only a 4" or so drop from elevator floor to basement floor. No big deal for people, but when taking a 2000lb machine thru the elevator it made things interesting. :)

Just thinking of that building brings back memories! There was a rat that lived in the basement that the workers nicknamed Grandpa, and when it was finally killed, it weighed about 35lbs. That building was so old that it still had a few 110VDC outlets! I'm not sure if they were still live, but the mechanic that worked down thought it was, but we never checked, as we had nothing that ran on 110VDC anymore. The NYC building inspector wouldn't go into the basement as he was afraid of the rats that lived down there, so instead of going down there, he just passed the building.

[JIMinPHX]

The last of the DC power systems in NYC were shut off by Con Edison while I was working as an apps engineer in the Bronx. That happened around 97 or 98. At that time, we either sold M-G sets to the last of our customers that were still running DC elevators or else we sold AC motors & drives for an upgrade.

There were still people buying DC power across the old Edison system up through the late 90's in NYC. Thomas Edison had pushed for power to be sold as DC. One of the reasons may have been because the bamboo filament light bulbs that Edison sold lasted longer when run on DC. I think that it was Nikola Tesla (backed by Westinghouse) that pushed for power distribution to be changed to AC. Obviously, AC won out. The reason being that AC power can be run through a transformer & DC can not. The transformer allows higher voltage to be sent across long distance distribution lines, which greatly reduces power loss. The details of all that get a little complicated, but that's the oversimplified basics of it.

Tesla had some truly dangerous ideas about distributing power through the open air, without the use of wires. He burned down a few facilities trying to perfect his methods. That's where the Tesla Coil came from. He also ruined the building that he had a shop in (on Canal St. in NYC I think) while doing experiments on sympathetic & harmonic mechanical resonance. He proved that a large building could be taken down with a series of small impacts from a small tool as long as the frequency of hits was tuned to the correct critical frequency. If you google " galloping gurdy" you should come up with some impressive videos of the Tacoma Narrows Bridge demonstrating this effect with disastrous results.

Enough with the hijack, Hows that new controller working out for you Mike?

[Frozone]

The inrush current would be of major concern for a 700 watt purely Resistance load like a furnace element.
(The inrush current on a conventional 100 watt light bulb is 17+ AMPS for several milliseconds. Then the element is white hot and drops back to the nominal 100 watts.

Here (http://wiki.answers.com/Q/What_is_the_difference_between_a_resistive_load_an d_an_inductive_load) is why you would be best suited to write this fool off as not knowing what he's talking about.

I quote:
"Resistive Load An electrical load which is characteristic of not having any significant inrush current"

Inductive or capacitive loads have inrush, Resistive inrush can for the most part be ignored.

@JIMinPHX - It was Westinghouse, who 'bought' (althougth he never paid for) Tesla's designs and set up the first major AC power company (a Niagara falls generator station).
Edison launched a smear campaign to discredit AC power. Including use of Ac to electrocute an (IIRC) elephant.

[JIMinPHX]

Frozone,
Thank you for the history check. I was just talking off the top of my head & a few of the details may have become a bit blurred over the years.

Sonny mislabeled the load as resistive. It's actually an incandescent load, which is a separate category. Normally resistive loads are rated for 1x inrush, inductive motor loads are rated for 6x inrush & incandescent loads are rated for 10x inrush when sizing equipment to control them. That is why a 30 amp lighting contactor costs more than a 30 amp motor control contactor. The 30 amp incandescent load is actually a heavier load than the 30 amp motor load. The 30 amp incandescent load actually requires heavier equipment to handle it.

Larger inrushes do exist for infinitesimal periods of time, but they happen so quickly that they do not produce noteworthy effects. For similar reasons, it is legal in some European countries to run 15 amp ground wire on contain types of 100 amp circuits. The duration of a 100 amp short circuit that is required to trip the protective equipment is so small, that there is not enough time for the 15 amp wire to heat up & cause a problem.