PID forge upgrade (videos added)

I think anyone confused need to read the Two-Stage PID Controlled Forge sticky. The process is very simple, ant does not need proportional control.The whole setup can be made for around $100.
https://www.bladeforums.com/threads/pid-controlled-forge-heat-treat-oven-plans-wip.1385057/

You need a:
PID - Any inexpensive PID controller will do. It only need SSR output contacts for our use (all of them have this).
SSR - A Solid State Relay ...SSR ... turns the solenoid ( or any load device) on and off. 40 amps is a good size. Even though the solenoid will draw a very low current, the 40 amp SSR will not need a heat sink. If the SSR has a built in heat sink, so much the better.
Solenoid - You want a 120VAC on/off gas solenoid valve that is rated for propane/natural gas. It should be rated to 15PSI. 1/4" ports are the best size.
Needle valves - two simple 1/4" needle valves, some elbows/tees/pipe/hose/etc.
Thermocouple - Type K thermocouple, 8 to 10 gauge (1/8") size is what you want. You want one with the round spacers to keep the leads apart. Thermocouples are polarized, they must be wire correctly.
TC sheath - For a forge, you need to protect the TC from the flame. A ceramic TC sheath that fits the TC with the sacers on it is usually a 3/4" sheath.
TC block - A TC mounting block is the best way to connect the 1/8" TC leads to the 20 gauge wires going to the PID.
TC wires - You need type K wires to connect the PID to the TC. The wires ar polarized and balanced to make the reading accurate. 20 gauge is a good size.
 
Cushing H. said:
That thing is going to click back and forth multiple times per second, or faster depending on the temperature
Click to expand...

I first saw one of these in action a few years ago at John Emmerling's shop. IIRC, his cycled once every second or 2 and was simply and on/off valve for the propane with the gas flowing about 1/2 the time the forge was running at welding temps. I remember thinking that he must be saving a lot on propane, with it off 1/2 the time.
I realize that the savings will be different with high/low instead of on/off, but I'm hoping that will be offset by the less frequent cycling I should have by having the burner always burning, as opposed to introducing cold air into the forge when the solenoid is OFF.
 
Cycling one every second or so would not concern me, i was concerned about a setup where the thing is trying to cycle ten times a second or so. Of course, how it behaves will depend on your parameter settings....

The behavior you just described, and stacys comment that “the setup does not need proportional control” sounds to me like a PID with parameters set so it effectively acts like a simple thermostat ... which was my whole point.... :-(
 
Cushing H. said:
“the setup does not need proportional control” sounds to me like a PID with parameters set so it effectively acts like a simple thermostat ... which was my whole point.... :-(
Click to expand...
A PID does a LOT more than a simple "OFF/ON" switch. It will anticipate when it should OPEN or CLOSE valve before the setpoint is reached to allow holding a closer temperature.
 
It is a bit more complicated than a simple thermostat, but I get your point. Effectively, they are both On/OFF devices.
Sort of like saying, "A golf cart is effectively the same as a Mercedes Benz". Yes they both will take you from place to place, have four wheels, and a motor. But, that is where the similarity ends.

The PID in this use operates as an ON/OFF device that operates another device that feeds fuel to a third device .... all done with auto-intelligent control to learn timing and to give tight flame control by self programming. Add that to a by-pass and you get very tight temperature control with no "WHOOF". If you don't know what WHOOF is, run your forge for a few minutes then turn the gas valve off for 3o seconds. Turn it back on quickly and you will get a big WHOOF of flames out the forge ports. The two stage system never has the flame off, so it just goes from LOW to HIGH flame, with those limits pre-set.



The two-stage PID controlled forge system was something I came up with (invented??) a long time ago. It worked very well, and instead of trying to patent it and sell the units, I gave it free to the knife making community. Many have built them and the results are quite good. Even for forging it helps by keeping the temperature range where you want it. If you are forging a blade and leave it in the forge too long the steel may well burn and be ruined. If it is in a PID controlled forge it will sit at 1950F (e.g.) and the blade will not get hotter than that. This is especially good when working several blades or billets at the same time. A pointed out earlier, some steels have a very tight forging range. Go even 50 degrees too high and it will crack or mush apart.
 
Thanks for all the input and thoughts everyone.
I think I'm about ready to order the parts, but still have a couple of murky items that I'd like a bit more clarification or opinions:

1) If cost or space is not an issue, is it better to go with a 40A SSR without a heat sink (cheaper and less space needed) or 25A with heat sink (more expensive and needs more room)?

2) Is it a waste of $ to have 2 NC solenoids (one at the regulator for safety shut-off and a second, 3-way for choosing high/low flow of gas, see post #8) or is the extra redundancy a good thing here?
 
Arrghh. You guys do not understand what I am saying (or I am just saying it badly). Ken - I know very well what a PID controller is and what it does - I have been using them for almost 30 years, and recently coached my son (now a senior mechanical engineering student) in implementing one from scratch in software and then tuning it.....

Guys, my concern (question?) is this: most PID controllers work by varying the control output, when in the proportional band, by sending out either an analog continuously varying output, or by using pulse width modulation. If you are driving a solenoid valve, the continuously varying output is kind of meaningless (the solenoid wants either a given voltage or no voltage applied). If it uses pulse width modulation, then what is will be trying to do is open/close the solenoid in rapid cycles. If the on/off cycles are too fast, the solenoid just will not physically have the time to react to the control signal. If you are fortunate enough to buy a PID which gives you significant control over the pulse width (like apparently in WEO's example) so that you can define a minimum cycle increment of, say, one second ... then that should work and allow the solenoid time to react physically - but you need to be careful that you actually have that capability. And also, if you have a cycle time like that, there should be no need for the rapid reaction times that a SSR affords, and you should easily be able to use an old fashioned (inexpensive) electromechanical relay.

Stacy - if you use the PID with "proportional turned off" ... then you are setting the proportional band width to zero .... and you are then running the thing as a simple thermostat ... and there is no "learning" or "intelligent" control that the device can exercise.....
 
Hi Cush. I'm wondering if you are thinking too much about this and focusing too much on the theory of PIDs instead of the actual real world usage. I think I understand your concern about the cycle time of the solenoids, and would say that this might be an issue in a laboratory setting where you might be looking for EXACT control over your temp with minimal to no fluctuation. In this situation, I could see the PID continuously cycling the solenoid faster and faster to try to maintain a steady, exact temperature.

Whereas in my, "real world" system, I'm not looking for that much accuracy, more of keeping the heat in a range. So, in my way of looking at things, your concern about the quick reaction times are a non-issue.
But, I do want the system to learn how to minimize the overshooting, which justifies the added $30-40 of going with a PID over a simple thermostat.

I hope that makes sense to everyone else (it does to me, at least:cool:;))
 
I am not thinking about this too theoretically, and I am not shooting for”exact” laboratory control (even if such did exist) - I am actually saying exactly the opposite. What I am trying to say is that this will effectively act as a thermostat, and also that you don’t need the SSR. This setup is spending money assuming you will get “learning” and better control ... and that added benefit will be minimal if present at all. This will work, but you could get essentially the same thing and spend less money with the same level of control.
 
Stacy - i respect you, and have learned an incredible amount from you. But that comment is condescending and unbecoming of you.

PID controllers are simply not as “intelligent” and definitely do not “learn” as some here have tried to describe them (or at the least that is a very stretched description of the integral function). There are times when they are not doing what you think/expect them to do - including acting ad a simple thermostat. I have been working with PID controllers for several decades - including creating them from scratch from software. Please accord me the possibility that i have a point to make in this case instead of just dismissing me as “not having built a forge”

sometimes they are expensive overkill. To use your earlier comment - you might buy a mercedes to drive on the golf course paths, but ..... why?
 
I almost didn't post it, but decided to before someone else did. There is a difference in knowing what a PID is and does and building a forge and running one off a PID. There is a lot more to it and using a forge.
BTW -The main reason we didn't use proportional control for a forge is the much higher cost of proportionally controlled gas valves. The simpler two-stage control system worked just as well.

You might like to read some of the threads from the folks who have built and fine tuned these forges. Eric Fleming, Nick Anderson, and Fred Rowe are great guys and would be glad to discuss it with you by PM or email. Eric and Nick haven't been posting for a while.
You should be able to chat with Eric through his website: Eric Fleming - http://www.flemingknives.com
Fred Rowe - http://bethelridgeforge.com/

Fred's forge build - https://www.bladeforums.com/threads/dual-controls-for-blown-gas-forge-tutorial.599953/
https://www.bladeforums.com/threads/vulcans-chariot-is-ready-to-tune.540299/

Nick Anderson's build - https://www.bladeforums.com/threads/pid-controlled-forge-heat-treat-oven-plans-wip.1385057/

I'll drop it there, as there is no point of arguing semantics about what we basically agree on.
 
Stacy - I just dont think you are even hearing what I am trying to say and are responding to a statement that I never even made. Your design for the parallel two-valve forge is great, and I never said anything about a variable ("proportional") valve. I ONLY said that you might well be able to save some $$ and configuration headaches by using a simple thermostat instead of a more expensive and complicated PID, and still get basically the same performance. again - you are being dismissive and condescending instead of trying to understand what I am trying to say.
 
Good morning all.
First off, allow me to thank everyone for their thoughts and input in helping me upgrade my forge. Your time and efforts are appreciated. I'm now going to ask that the rest of the public posts be limited to the specific overall design and components of my forge upgrade. After all, it's my world, and therefore everything's all about me, right?:p

Last night I was talking about my plans with another blacksmithing buddy over dinner and he asked me a question I didn't have an answer to: Why should the NC valve be wired in parallel with the blower instead of in series? His thinking is that if they are wired in parallel, and the fan were to somehow blow out, there would still be current flowing to the solenoid, keeping it open, but if they are wired in series, then they both would lose current and the valve would close (which is what I'm shooting for).

Again, thanks for the efforts and I look forward to getting this up and running.
 
"IF" both fan and solenoid are 120 vac and the supply is 120 VAC, fan and solenoid MUST be wired in parallel so both fan and solenoid get 120 vac. If they are wired in series then each would receive only half voltage, or 60 vac each.

If the 120 vac supply is lost, then both fan and solenoid would shut down. Perhaps the best way to wire would be to wire the two wires (not 'n neutral) to fan first, then jumper from fan to solenoid. Wired in this manner the odds of the solenoid having power when the fan lost power would be exceeding slim.
 
Ken H> said:
"IF" both fan and solenoid are 120 vac and the supply is 120 VAC, fan and solenoid MUST be wired in parallel so both fan and solenoid get 120 vac. If they are wired in series then each would receive only half voltage, or 60 vac each.

If the 120 vac supply is lost, then both fan and solenoid would shut down. Perhaps the best way to wire would be to wire the two wires (not 'n neutral) to fan first, then jumper from fan to solenoid. Wired in this manner the odds of the solenoid having power when the fan lost power would be exceeding slim.
Click to expand...
or use a solenoid activated by the blower circuit to activate the solenoid power supply? To your point though - not sure if this would unduly decrease the voltage supplied to the blower?
 
Ken H> said:
"IF" both fan and solenoid are 120 vac and the supply is 120 VAC, fan and solenoid MUST be wired in parallel so both fan and solenoid get 120 vac. If they are wired in series then each would receive only half voltage, or 60 vac each.
Click to expand...

Ahh....that's right, I forgot about the drop in voltage when wired in series... Thanks Ken!
 
to be clear - my comment regarding a "solenoid" was really meant to mean a solenoid activated relay. I was thinking it might be possible to find such a relay that had a much lower voltage drop than the solenoid in the valve that you are currently considering. solenoids operate on current - it might be possible to find one that will be activated by the current flowing through the blower circuit without unacceptably lowering the voltage to the blower? (voltage will not be evenly split - it will be split by the relative resistances of solenoid and blower. if the resistance of the solenoid is really small, it might be acceptable to have it in series with the blower).
 
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