Arduino PID build

[mjwcaster]

So I finally started on my Arduino based PID build the other day. Not a rush job, I bought the arduino for 3 years ago to play with and the SSR/thermocouple 6 months ago.
I threw a simple temp measuring circuit together the other day and just tested it out in my lead pot today.

Prototype in custom enclosure




Fancy roll around stand for custom PID enclosure




Hand crafted mount for thermocouple (bent wire).


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[mjwcaster]

I was just doing a quick session to work on some molds, loose sprue plate and reseating alignment pins.

The Arduino measures temperature, but not the same as my TruTel 200-1000F analog thermometer.
The Arduino reads 10F low over 800F
And 30F lower at 650F.
60F lower at 410F (Arduino reads 350F)

So that’s a bummer.

My TruTel is high and on an angle, need a better mount. So after I turned the pot off I check the temps while cooling paying extra attention to reading the TruTel from as straight on as possible.

Still increasing difference as temps drop, so not a constant offset which would be easy to deal with.

Arduino read true enough on Ice water at my desk, need to check other points.

Also the sprue plate screw is beyond stripped on my 356-95RF, was my best running mold. Time for an oversized bolt, if I can find my tap set.
At least the alignment pins on my 452-230TC are closer now, bullets almost useable. Hopefully one more try and I’ll have round bullets again.


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[LaPoint]

Bread board prototyping has now become Amazon boxing? Your project looks very good!

[SteveM54]

Man, I love the fact that projects NEVER end - until we get to that 6' deep hole.

[mjwcaster]

Round 2
Rigged up my SSR to test it.
Threw in in a baby wipe box, used a computer power cord, duplex outlet, and spare 2 conductor wire for control.
I set it up stand alone so I can use it with different devices. I will probably try a Rasberry Pi in the future. And I ordered a cheap Inkbird PID to use, should be here tomorrow.
Used a 6v wall wort to drive the SSR and ran my pot for a couple of hours. Worked fine and the SSR in the box was cool to the touch.
So far so good.

Outlet in side of box


Power cord and control cable



Lovingly secured components



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[mjwcaster]

Round 3
I’ll call this round a confusing win.
Last round I pulled the thermometer and thermocouple out of the Lee 4-20 in preparation for my pure lead calibration test.
So today I tried melting my pure lead in a ‘tin’ can, it was a failure due to poor heat transfer.
But while that wasn’t working I had the 4-20 heating up, once liquid I stuck the probes in both read 720F
I took extra care to get them as close to the center of the pot and each other.
Both the TruTel and Arduino read exactly the same up to 800, confused but happy I powered off for phase 2.

My Inkbird 106VH pid showed up today so I moved the thermocouple and SSR wiring onto it and powered up again.




The only programming I did was change P to 1 and unit to F.
Set the temp to 750 and let it rip.
Pot temp had fallen to ~700F, ran up to 760F then dropped to 740F.
Only ran it for a short while but it maintained +-10F out of the box, not bad.
It read within a few degrees of my TruTel, close enough.

I have another thermocouple coming in tomorrow so I can keep playing with the Arduino and will order another SSR to go with the Inkbird for a clean build.

Time to open up the convection oven and rewire it for PID control.


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[Tazza]

Very cool setup, my master caster is run with an arduino uno, it has cast close to a million round things and it's still on the original Arduino.

Did you get code for the PID function? or are you just using it as a normal thermostat?

[mjwcaster]

Very cool setup, my master caster is run with an arduino uno, it has cast close to a million round things and it's still on the original Arduino.

Did you get code for the PID function? or are you just using it as a normal thermostat?

Fancy thermometer until tonight. I just added the code for PID, hard coded temp and K values, compiles ok.

I plan on hooking up the new thermocouple and trying out the code tonight.

So far I’ve just glued together parts from different example programs and while it might work looking at the code makes my brain hurt.
It’s been over 20 years since I got paid to code, but I still have some standards.
If this works tonight I will do a rewrite/cleanup then work on the user interface.


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[Tazza]

Fancy thermometer until tonight. I just added the code for PID, hard coded temp and K values, compiles ok.

I plan on hooking up the new thermocouple and trying out the code tonight.

So far I’ve just glued together parts from different example programs and while it might work looking at the code makes my brain hurt.
It’s been over 20 years since I got paid to code, but I still have some standards.
If this works tonight I will do a rewrite/cleanup then work on the user interface.


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I hope it works out well, no reason it won't, an arduino i assume would have more computing power than a regular PID controller does.

Clean code is nice code. My brother is a code monkey for a living, i could spend hours fiddling trying to make it work, he spends 5 minutes and it's working perfectly.

I know programming is very logical, it's just not something i have spent much time on to get better, i just know it will frustrate me when things don't go right and no doubt, they will be simple mistakes.

It will be interesting to see how reliable the arduino is. The arduino i use for my casting machine every so often glitches, i assume from EMF.

[Rickf1985]

Are the foreigners nuking your islands again down there? You need to build a lead shield around your casting room. LOL. Nope, that wouldn't work for long, you would melt down your shield for the lead.

[mjwcaster]

Reliability is a good question, I don’t have great expectations.
System design by a hack using Chinese knockoff components.
When you start with an SSR that might be labeled 40amps that probably has a triac inside labeled 25 amps which is probably overrated itself you can’t expect much.
This is more just proof of concept and for fun.
There is a reason good components from Auburn and Crydom cost 3-5 times as much.

And I am basically relearning circuit design, been 30 years since I played like this. Even when I worked at an electrical engineering firm I didn’t do circuit design and even moved on from programming quickly to network and customer support.
It’s kind of fun , kind of frustrating.


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[mjwcaster]

So I finally got around to trying out the PID code while working on the minivan (daughter just got her license).
It works, kind of. Needs tuning, slow response and wide temp swings +/-40f.
Also the temp readings are bouncing around a lot, within 15f but not steady at all. I needed to reseat some wiring when I started just to keep everything running, it’s a mess.
I’ve also misplaced my code in a computer HD swap, not sure whether it’s worth the effort to dig through disks/backups to find it or start over someday.

For now I have the real PID to work if I need to cast.
I really wanted to play with a raspberry pi, but they are MIA right now, pricing makes primers look cheap.

For now I’m going to close the arduino up in its box and clean the garage for our new toy, a cheap stick welder. My daughter just started welding in school and likes it so we went halves on a welder.

Someday I will get back to playing with the PID build, but I haven’t even cast in months.


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[Tazza]

That is a wild temperature swing right there, I'm sure it's something simple that is causing it to not maintain it correctly.

Good move with using a regular PID, they are so cheap, if it burns up, just replace it. I am on my third one on my Master Caster, i feel 800,000+ projectiles so far, i'm doing ok on the PID front.

Glad your daughter is interested in welding, it's a good skill to have. Depending on the welder, some are mighty cheap and do a reasonable job too.

[Mike W1]

I'm pretty sure at this point the OP knows things I certainly don't about programming things. I am also quite certain 99.9% of bullet caster don't know any of that either!

Why anyone would spend the kind of money an Arduino (or whatever it's spelling) to control temperature is beyond me and most of us 99.9% ers. Apparently my $12 Rex's do as well or better without the hassle and my Auber certainly does. About a 4 time jump in price on the Arduino from the Rex. Even my Auber unit wasn't quite that much of a price difference and it does read in F or C whereas the Rex is only in C.

Bad enough for most of us to setup a Rex, Mypin or Auber, please don't encourage the mass of us know nots toward something like this type.

[mjwcaster]

That is a wild temperature swing right there, I'm sure it's something simple that is causing it to not maintain it correctly.

Good move with using a regular PID, they are so cheap, if it burns up, just replace it. I am on my third one on my Master Caster, i feel 800,000+ projectiles so far, i'm doing ok on the PID front.

Glad your daughter is interested in welding, it's a good skill to have. Depending on the welder, some are mighty cheap and do a reasonable job too.

The temp swings are just PID values that need adjustment, not even sure what I stuck in there.
There are auto tune libraries available if wanted.
Or just copy the values that I used on the MyPin.

The arduinos and Raspberry Pi are normally cheap, but not right now.

The welder is a Chinese $130 special that gets decent reviews.
I just need to get a 6-50 plug end to make an extension RO run it on 220 in my garage.
So 110 for now.

My daughter just got her license the other day and we just got more work done on the minivan tonight.
Even with oil dripping in her face she says she would rather do something with her hands than work in an office.


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[Plate plinker]

Interesting

[Tazza]

The temp swings are just PID values that need adjustment, not even sure what I stuck in there.
There are auto tune libraries available if wanted.
Or just copy the values that I used on the MyPin.

The arduinos and Raspberry Pi are normally cheap, but not right now.

The welder is a Chinese $130 special that gets decent reviews.
I just need to get a 6-50 plug end to make an extension RO run it on 220 in my garage.
So 110 for now.

My daughter just got her license the other day and we just got more work done on the minivan tonight.
Even with oil dripping in her face she says she would rather do something with her hands than work in an office.


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My stick welder is a telwin, i got given two broken ones that i made one good one from, DC inverter and i love it.

I wish my wife would pick up a wrench from time to time to help me, but it's just not her i'm afraid. I'm glad she likes getting her hands dirty and learning how mechanical things work. My wife knows where oil, water and fuel goes in her car, that is as far as it goes....