PID Controller

[Ben]

I talked to Al Nelson with NOE Bullet Moulds today. He mentioned he was wanting to make a Digital PID for casting and or powder coating.

According to Al :

NOE has started looking at possibly making our own lead pot and while it is too early to say too much about that, we do want to talk about an off-shoot of that project. While doing preliminary design work on the pot we decided it had to be PID controlled from the outset so we sat down with an electrical engineer and designed a PID controller to use with our new lead pot.
We did a number of things to help make it simple, easy to use, easy to maintain, and upgradable.
First off, the design uses a standard computer power cord (C13 style plug). This means wherever you are in the world changing to the appropriate power cable shouldn’t be a problem.
Second, we are looking at making two versions one using 120V and the other using 240V so the units will be usable worldwide.
Third, we are using a mechanical switch (Contactor) as solid state relays are not recommended for the currents most melting pots require. That switch is a standard HVAC part so if it wears out, it can be easily and inexpensively replaced at any HVAC supply store.
Fourth, we used a standard K-type thermocouple probe which allows easy replacement via a socket on the unit face rather than being hard-wired. This allows users to pick a probe length anywhere from 4 to 14 inches depending on pot size.
The unit is fused for 15A at 120V or 30A at 240V to work with most conventional house circuits.
Both the hot and return lead are switched for an added safety margin.
Temperatures can be set between 50F and 932F (10 and 500 C) and can go as high as 1200 F (650C) with a probe change.
The unit is roughly 8 x 5 x 5 inches ( 20x12x12cm) and will come with a 20 Amp rated 120V or 240V outlet depending on the model ordered.
We are looking at a price point around $200 USD and hope to be ready to ship early next year.

 

[popper]

solid state relays are not recommended for the currents most melting pots require

Needs a different engineer.

 

[Glaciers]

What size pot? 20 - 30 pounds? Any idea

 

[Ben]

I'm not certain ?
I think as Al gets closer to shipping, there will be quite a bit more info. available on this web site.

Ben

 

[Tomme boy]

Yah he needs someone other than eagleeye to talk about this. We ran 2 1500W heaters on dies that sealed plastic with one SSR's and they lasted years. And they ran 18 hours a day 6 days a week. The only time I remember changing one was when something went really bad and they were changed just because.

SSR are cheaper and safer. Faster, more compact. Don't require as big of a heatsink if any depending on what it is used for.

 

[hporter]

What size pot? 20 - 30 pounds? Any idea

That was my first thought too.

If he does a 20lb unit, he has a lot of competition.

If he went larger, he would have guys like me with too many pots already, very interested.

Needs a different engineer.

I wondered about that too. I built my PID about 10 years ago with a SSR and it has worked flawlessly. And they are super cheap and easy to get on the net. Actually aside from the SSR, his proposed PID sounds exactly like what I built.

I wish him the best of luck with the new products. He makes good stuff.

 

[Bret4207]

I'm also in the 30+ lbs pot group. I see little sense in joining an already fairly crowded market with a 20 pounder, but 30-40 lbs is a whole different thing, especially if it's state of the art and less expensive than, say, RCBS or Lyman.

 

[Rick H]

My cheap homebuilt is running fine with a cheap SSR. If it goes bad I will just replace it for under $10. Most of the cheap ones are imported from China and perhaps there is a supply chain issue that he is concerned with.

 

[Glaciers]

Yeah everyone builds a 20 pound pot, but 30-40 pound would be of interest to me. I would think that Al’s customer base are serious casters so a larger pot might sell.

 

[Rick]

Another 20 pound pot would be very ho-hum. 30 pounds Plus would be very interesting with the top large enough to easily accommodate the Rowell 2 pound ladle.

 

[Glaciers]

I think the Magma pots are 40 pounds, but over $600. That’s not happening. Starts cutting into gun money.

 

[hporter]

Al’s customer base are serious cast

That is an excellent point, and I have to admit that it hadn't crossed my mind.

I guess folks buying multi-cavity custom molds would be the first to recognize how fast you can drain a 20lb pot - and see the virtues of a larger capacity one.

My buddy just bought the 40lb Magma, but I can't see myself dropping that much money on one either. But it was his first pot, and I think he subscribed to the "spend once, cry once" philosophy on that one. I'm hoping Al will come up with something similar at an affordable (or more affordable) price.

 

[Rick]

Yep, Magma is a 40 pound pot. Bought mine new from Magma for $450. At that time they didn't offer a PID, I added it a couple of years later.

 

[Glaciers]

Yeah I have a NOE 5 cavity 45 caliber 304 grain mold and it sucks the mix pretty quick.

 

[JonB]

I wonder if Al's business liability insurance will require him get his products (Furnace and Controller) UL inspected and labeled ?

I also have concerns about the use of mechanical contactors with a PID, but I suppose there are settings to slow the cycle rate. Also, there are electronic temp controllers that aren't PID, that will keep the temp of a lead pot within a few degrees, that utilize a mechanical contactor.

 

[KeithB]

An SSR with an adequate heat sink is the way to go IMHO.

 

[Ian]

Al definitely needs to talk to someone else. No way mechanical contactors will last any decent time with typical PID PWM frequencies. SSRs are cheaper and far, far better, and can run as many amps as you want if you only buy the correct size and cool it per its particular needs. SSRs are very common and a zillion companies make basically the same size options so you can replace a bad one easily with any brand of the correct specs anywhere in the world.

40 pounds or don't bother.

I have a parts list to build a 40-pound, 2500-watt, PID-controlled, SSR-driven, K-thermocouple furnace for about the price of a Lee Pro 4-20. Only holdup is I don't yet need one badly enough to move it to the top of the project list.

 

[Tomme boy]

Another thing I would do is not cheap out on the PID controller. A Honeywell would be my choice. Second would be Omron. I have used these and know they work well.

 

[Ben]

An Up-Date

We talked with the engineer last night and ordered some parts for alarm circuits and also a couple of high current SSRs just to test with. If the feedback is some think an SSR will perform better, let’s test both and take whichever wins. In asking, the engineer thinks heat will be an issue for the SSR and the 2nd engineer, thinks the mechanical may indeed require that the control be less precise to keep from oscillating the contactor. This is why we ask for feedback, so we are now looking at two versions of the controller one with the mechanical contactor and one with an SSR. We are keeping the safety feature of using a dual channel relay so all voltage will be cut regardless of mis-wired outlets.

We are concentrating on the PID first and hope to move on to a lead pot next. My thoughts are like others, a bigger pot (30Lb or 40Lb) is in order.
One step forward….. but it should help insure we get the best product to market.

NOE Owner
Al Nelson