My New Dual PID controller

[edctexas]

Thanks again to the wonderful people that post info here! I want to show the Dual PID I built from pieces of my junk box and Auberins. Auberins is a great full service place. A little higher price, but their gear is in stock and quick to ship.

I built this to have one PID trained for the pot and one for the hot plate or the oven (PC baking). Experiments showed me that the trained settings were not to different for the plate of the oven, so I just made one box. I had thought about two boxes, one single and one double, but this works great.

This is the front panel.122237

This is the Rear Panel.

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This is the insides. I tried to route the AC, SSR control, and the TC wires separated to avoid any noise coupling. The input AC is fused and filtered . Separate On/Off for PID one and two. Not shown is a bypass for the PID control for PID #2. This allows the oven or hot plate to warm up with out the TC sensor.

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I do not know how to make these larger yet, but hope that this helps anyone thinking about building a PID. I have built analog ones years ago but this digital one works better and is much simpler to employ. If anyone has questions, please feel free to PM me. The PID makes the Lee Pot work well and I knoe what my lead temp is (less variables). I preheat my molds on the hot plate with an aluminum plate on top to mount the TC sensor. Some day I make get the NOE mold sensor thermometer. But pre-heating means no more than one or two casts before good boolits.

I hope that the ESPC process works for me. At least the boolits look nice and I do not see leading in my experiments. More on this in the coatings section.

Ed C

[bigarm]

Would like to see a picture of your hot plate with the aluminum plate to mount the sensor.

[Beagle333]

Nice job!

[mattw]

Good looking job, but where are the heat sinks and SSR's?

[edctexas]

The SSRs are mounted to the sides of the case. They are above and below the Auberin PID plastic case with a 1 and 2 in red. I removed the power coat from the metal on the case inside wall with solvent and sanding. I polished the metal with 600, 100, and 1200 grit and mounted the SSRs with leftover PC processor heat sink compound. These are 25 Amp SSRs and the peak currents are less than 9 amps. The case does get warm, but less than 50C. After the pot gets up to temp, the case cools as the time on is small.

If you still can't see I'll post another pix.

I will post a pix of the plate for the hot plate. It is roughly 7" square and 0.125 Aircraft alloy (came from Lockheed Martin scrap). The TC is mounted to an edge. It has several screws protruding from the bottom so you need to lift it off the hot plate. I did bump it off once in the prototype stage. I have a stepped piece of scrap on the front edge to catch the hinge on the mold handles. One step for LEE, Lyman, and NOE. This allows the mold body to sit flat on the plate.

The other reason for the plate was that I tried heating ingots on the Hot Plate. DON'T DO THAT!!! The ingots melt and you lose lead and make a mess. With the plate on top, they can still melt but the melt does not go into the hot plate insides. Now I use a nice little cast iron pot so any melt is saved.

Ed C

[el34]

Really a nice and neat job Ed. These things are great, I'm thinking about sending Banger one for Christmas! :smile:

Sooner or later there'll be a realization that monster heatsinking is simply not needed. With around 7 amps and 1 volt dropped across the SSR itself, 7 watts is generated. That's similar to an incandescent nightlight.

[ph4570]

Looks good. A tidy wiring job -- unlike mine.

[el34]

El34,
I agree completely. Heat sinks are overkill for a 9a current draw, the case will act as a heat sink. However, since most use 25a SSR's, I consider adding a heat sink as a better safe than sorry proposition. At some point in the future, the PID unit you use may be used by someone who has limited knowledge. Hook up the wrong device to it, and it could cause problems. Just my 2 cents.

Ed C, good job. Pics of the entire setup, PID, Pot, and Plate in operation would be good.

OB

I looked at datasheets for Crydom SSR's, the industry standard 'good stuff' in the US. The only goal was to see differences in the 25A and 50A versions.

Both had the same 1.15V drop across themselves (measured at full load, it would be less at 7-9A).

The 25A had about half the thermal resistance from junction to case, meaning internally generated heat would conduct to the case bottom more efficiently but all that really translates to is you can operate the thing at a higher ambient room temp.

The Lee pot heater is 700W. At 110VAC that means 6.4A, and with 1.15V drop the SSR will therefore dissipate 7.3 watts. Same heat as a nightlight bulb. With no heatsink they can operate up to 176deg F at 7A.

I'm not lobbying against heatsinking, just hoping to put perspective on it based on data.

The Chinese SSRs may have a higher voltage drop across them, which would make them get hotter, dunno.

Crydom's list and specs of AC SSRs-
http://www.crydom.com/en/Products/Catalog/c_s.pdf

[John Allen]

That came out really nice. I have thought of doing the same thing.

[dikman]

Very impressive data sheets, el, but one thing they don't say is where they're made. Interestingly, right at the end it refers to environmental compliance with Chinese regulations. Rather strange, unless that's where they're made?

Yes, I know, I'm being picky, but that's what I'm like :bigsmyl2:.