Project - PID on Lee Pro 4 20 furnace

Let me start off by saying that I'm fairly new to casting. When I decided to get into it, I bought the Lee Pro 4 20 Lb Furnace because it was inexpensive and had good reviews in the user community. The only downside to using this furnace was temperature control. It has a rheostat with numbers from 1 - 10 for controlling the amount of current going to the coils to heat up the lead.

This created an issue for me. In order to tell what temperature I was at, I bought a VWR Traceable Workhorse Thermometer 4425. I would constantly have to check the temperature and could only maintain it within 20°F - 30°F of my desired 700°F. It was a pain to do and time consuming. Occasionally, I would find myself way above the desired temperature resulting in burning off my tin and causing some nice colors to form on top or I'd find myself way too low and my pours would slow down to a trickle. There had to be a better way other than buying another pot that had temperature control.

The solution is to install a proportional–integral–derivative (PID) controller to the pot and let it maintain the temperature for me. As a coffee geek, I had heard of people using these to control the brew temperatures of the espresso pours to within 1°F accuracy. I almost bought this for my Isomac Millenium espresso machine but then learned it isn't very effective on heat exchanger type machines such as mine. I had also heard of people using these for Sous Vide Cooking and almost bought one for this, but didn't. So now I thought this is the perfect opportunity to finally get to use a PID controller to solve an issue that I was having.

As I researched this, and not to my surprise, I found others had already done it. Through postings of others, I was turned on to a website auberins.com, Temperature control solutions for home and industry. It had all the equipment I needed at and at reasonable prices to achieve my goal. I placed my order for my parts and got them in yesterday. Now the project begins...

The goal is to have a furnace that I can set the desired temperature and this temperature will be maintained with no interaction by me to within 10°F. The PID controller should maintain it within 1°F so my goal should be easily met. My other goal was to install this as part of the furnace rather than as an external box that the furnace plugs into. The external box is simple and can be easily used for another purpose so there are benefits to it but I want a clean single unit to plug in, melt lead, and store.

Here is my somewhat dirty Lee Pro 4 20 Furnace that I am starting with.

http://img30.imageshack.us/img30/8205/leadpot.jpg

Here is the equipment that I bought from auberins.com, Temperature control solutions for home and industry.
It includes:

• 1/16 Din PID Temperature Controller (SSR control output)
• 25A SSR (Solid State Relay)
• Heat Sink for SSR
• K type high temperature thermocouple
• Compact extruded aluminum box for 1/16 Din controller
• Panel mount for K thermocouple
• Flashing Buzzer

http://img199.imageshack.us/img199/4419/pidhardware.jpg

First step is to disassemble the Lee Pot controller housing. This consists of removing just a few screw on top and the bottom. As you can see, there isn't much to them inside. It is mostly just empty space. A rheostat and wires to the heating coil. I was glad to see this because it meant I had room to work with on my project!

http://img832.imageshack.us/img832/9...isassembly.jpg

I had been wondering where I was going to mount the relay and heat sink and after I had the Lee housing apart, I found that the relay barely fits within it; but not the heat sink. So I decided to mount the relay to the base of the Lee Pot and allow the base to act as a heat sink. The heat sink I bought came with some thermal coupling grease so I lightly coated the bottom of the SSR, drilled a couple of holes and screwed the SSR to the Lee.

http://img52.imageshack.us/img52/3011/relayprep.jpg
http://img19.imageshack.us/img19/434...yinstalled.jpg

I'll be following this thread with interest, Thanks.....Bill

Next step was to determine where to mount the aluminum housing for the PID Controller. I decided to mount it on the back of the Lee housing and low enough so that radiant heat won't have a direct effect on the PID controller face. I attached it with a couple of screws and then drilled a hole to pass a couple of wires for powering the PID and controlling the SSR.

http://img694.imageshack.us/img694/9140/caseprep.jpg

Now, I'm ready to start wiring it up. First was to get power to the PID. I soldered the wires onto the existing power wires to keep things simple and allow me to remove it easily if needed in the future.

http://img844.imageshack.us/img844/7476/powertopid.jpg

Next, I wired up the heater circuit to add the relay into the loop. Again, I did some soldering for a couple of wires and put heat shrink (green piece in pic) over the connector that used to go to the other coil contact.

http://img706.imageshack.us/img706/3...tercircuit.jpg

Finally, I ran a wire from the PID relay output to the relay and hooked up the thermocouple to the PID. Now it's all wired up and ready for re-assembly.

http://img847.imageshack.us/img847/5696/allwiredup.jpg

Re-assembly consisted of installing 8 screws for the PID housing and 7 screws for the Lee Pot housing. Quite easy and no left over hardware. :) The thermocouple wire was way too long for my needs so I coiled it up and tucked it in the PID housing.

Here is the final assembled Pot with the PID controller attached from all four angles. I still need to come up with something to hold the thermocouple in the pot and just off the bottom. I'll take care of that tomorrow.

http://img827.imageshack.us/img827/9933/final1b.jpg
http://img835.imageshack.us/img835/5708/final2m.jpg
http://img695.imageshack.us/img695/9006/final3t.jpg
http://img18.imageshack.us/img18/8066/final4y.jpg

Here is the wiring diagram that I used:
http://img21.imageshack.us/img21/176...ngdiagramj.jpg

It came out of the PID Instruction Manual.

I have not wired up the alarm yet and don't know if will use it. My initial thoughts were to set it to around 670°F so that when it came up to temperature and I added more lead, it would let me know that it was working on bringing the temperature back up. I'll play with it later and see if it is a useful function or if it turns out to be an irritation.

Now the final test of the night...plug it in! This is always a bit nerve racking for me. I've messed up a wiring project for a water cooled computer before and smoked the power supply. I plug it in and the PID lights up! No smoke so that's good. Everything seems to be working fine.

http://img707.imageshack.us/img707/415/poweredup.jpg

The PID started to display the temperature of the thermocouple: 78°F. I grasp it in my hand and see the temperature start to climb. This means I did not wire up the thermocouple backwards.

I bring up the temperature set point to around 120°F and stick the thermocouple in the pot. I hear the heater come on and it starts to get warm. About 30 seconds later, the temp of the thermocouple starts climbing until it reaches 120°F and then the relay opens to turn off the heater. Success!

There are a lot of settings in the PID. Tomorrow I will melt some lead and start setting up the PID. There is an auto-tune mode that I hope will take care of the settings for me. If this doesn't provide the control I want, I will then have to manually tweak some settings.

Here is the front panel of the controller. This is also taken from the manual but I thought I'd throw it in here to give you an idea of the flexibility of this little device.

http://img827.imageshack.us/img827/8307/frontpanelb.jpg

1. PV display: Indicates the sensor read out, or process value (PV).
2. SV display: Indicates the set value (SV) or output value (%).
3. AL1 indicator: It lights up when AL1 relay is on.
4. AL2 indicator: It lights up when AL2 relay is on.
5. A-M indicator: The light indicates that the controller is in manual mode. For the controllers with the Ramp/Soak option, this light indicates that the program is running.
6. Output indicator: It is synchronized with control output (terminal 7 and 8), and the power to the load. When it is on, the heater (or cooler) is powered.
7. SET key: When it is pressed momentarily, the controller will switch the lower (SV) display between set value and percentage of output. When pressed and held for two seconds will put the controller into parameter setting mode.
8. Automatic/Manual function key (A/M) /Data shift key
9. Decrement key ▼: Decreases numeric value of the setting value.
10. Increment key ▲: Increases numeric value of the setting value.
    
    
    
    
    
    
    
    
    
    

Cranium - This is absolutely terrific. I have been considering getting another bottom pour for keeping separate alloys. I am leaning toward the Lee you show here due to the cost. I'm not spending up for another Pro Melt. I like it a lot, but they're still a lot of money. Anyway, the only drawback to the Lee, as I understand it, is the temp control. Hence, guys wiring up these PID controllers. Nice job and thanks. And welcome to the forum. enjoy Mike

How much of a cash out lay was it if you do not mind me asking?

Tom

Very informative! I been considering putting a PID on mine as well.

Nice pictures.

I would disconnect the lee controls totally.
Also for mounting your probe, its easy.
I used solid 14ga wire. I stripped it down to the metal only and wrapped it around the probe.
I then used a crimp ring connector for mounting
http://img.photobucket.com/albums/v5...AwOTkuanBn.jpg
http://img.photobucket.com/albums/v5...AxMDAuanBn.jpg


the PID is $45 shipped
Probe is about $12 from ebay seller

The Lee pot has a 700 watt element. (700/120 = 5.83 amps)
You can use a 10 amp SSR and be just fine.

I am in the proccess of building one for a member on here.
I will take pictures of it once its completed.
It doesn't require taking your pot apart. Basically you just plug your pot into it, plug it in the wall, and hook up the probe.

I printed out this whole thread and also printed all pages from the Auber website. I don't know if I'm up to this project cuz I'm electricly challenged. If I decide to go ahead I'll probably have a lot of questions for Cranium. I get too many crazy ideas from this site. I want to do a bottom pour 150lb lead pot too. Retirement is busier than working.

Bob

You don't have to do what he did.
I will post up pics of my project next week.
I am awaiting the PID to show up. It should be here tuesday.

Nice job!
Would you mind posting links or model numbers for the parts you purchased?
Total cost?

Following this one. HATCH when you get yours up let us know, I'm interested in either.

I gotta get mine done. I have been wanting to PID my dang pot for about a year now. Funny thing is I will go out and drop $50-$100 on something that is totally worthless but when it comes to buying my components I always say "One of these days". I just need to order my parts.

Not bad!

Your only 'mistake' is to mount the PID face up, lead has a tendency to splash out and will ruin the plastic face of the PID.

I'm a little concerned about the SSR location. You are aware that even the base of the melter gets rather warm?

this is a basic parts list

Thermocoupler - http://cgi.ebay.com/K-Thermocouple-S...-/110681766757

PID - http://www.auberins.com/index.php?ma...products_id=14

SSR - http://www.auberins.com/index.php?ma...&products_id=9


My setup is a little different.
I will post pictures up later of mine.
I have to melt lead in order to remove the probe.. LOL

I appreciate the positive feedback on this project. I've always wanted to do a project with a PID controller and found the perfect opportunity. I'm confident about wiring up my espresso machine now. LOL

The wiring may seem a bit daunting but it really isn't. I soldered some wires only because I was too lazy to go to the hardware store and buy more crimp connectors. Electricity flowing through wires is like water flowing through pipes. Bigger wires allow more current just as with pipes and water. The relay is just a gate valve that blocks flow and the wires need to be run so the electricity can flow in and back out of your project. I think of electrical projects in this way sometimes because it is easier to visualize. And I was a nuclear mechanic in the Navy many years ago so water flow is more familiar than electricity flow. But it is easier to lay wires than pipe.

As far as parts, I spent $140 inc shipping. I didn't use the heatsink, thermocouple mount connector, and flashing buzzer so could have saved $25. And deduct the cost of the aluminum box if you have your own and you save another $25. So this project could be done for just over $90 shipped from Auberins.

Here are the parts for this project that I did use:

1/16 DIN PID Temperature Controller (SSR control output)
http://img831.imageshack.us/img831/7843/pidsm.jpg
K type high temperature thermocouple for heat treatment
http://img215.imageshack.us/img215/4...mocouplesm.jpg
25A Solid State Relay
http://img228.imageshack.us/img228/1598/25assrsm.jpg
Compact Box for 1/16 DIN Controller
http://img688.imageshack.us/img688/8...ojectboxsm.jpg

Frozone: I don't consider my mounting mistake. I did think of the lead splashing on the face of the controller. I need to be able to look and see the temperature I am currently at. This is especially true after adding more lead. I realized this may be an issue and am going to do a quick and simple cover for it out of some lexan I have laying around. :)

Hatch: Thanks for the suggestion on the wire. I was going to just use a coat hanger for today and may just use your idea. But I want to find out how much the temperature accuracy is affected by having the thermocouple so close to the edge before I decide on what to do long term. I want the thermocouple to be removable and not in the way of fluxing, cleaning the pot or adding lead.