Help Wiring PID Forge

silver_pilate

silver_pilate

Joined
Oct 30, 2002
Messages
3,974
Well, I'm a little thick when it comes to wiring, so I always make sure and ask a million questions before any juice ever runs through it.

I'm in the process of setting up a PID control box for my forge. I'm basing off of the schematics posted by Stacy and JT a while back in these threads:

http://www.bladeforums.com/forums/showthread.php?t=600318

http://www.bladeforums.com/forums/showthread.php?t=523845


Anyway, Here's where I'm at, and I have a few questions. I'm in the planning and layout stage right now. The gas solenoid I'm using has two identical wires coming out of it. Obviously one will be receiving the switched power form the SSR. Does the other on connect to the neutral? Also, my PID has no ground labeled on it. It does have two inputs for the AC, but there is no +/- or anything like that. So I'm assuming the hot and the neutral attach there. Since there is no labeled ground, should I ground to an unused screw (#6)? Here's the PID wiring diagram:

PIDWiring.jpg


Here's a really bad schematic of my wiring plan, keeping colors of the power cords the same (black=hot, white=neutral, green=ground):

Forge.jpg


This is off the top of my head (from my poor memory) of what I've layed out at the shop, so there is likely some mistakes. Please call them out as you see them!! Any guidance here is appreciated!! Thanks!

--nathan
 
from looking at your drawing it looks OK. let go through it just to be sure. first off the blower, PID and the solenoid will need to be wired straight to the neutral (white). now the hot leg (red wire) goes to a switch so you can turn it on and off. now out of the switch you go to the PID because it needs power to run. also one of the fan speed controllers needs a hot leg as well so it can run the blower even if the PID is off. next is the SSR, this is like a switch so you have to have something to switch. so the SSR gets a hot leg as well. this way when it is told to turn on it will send power from the hot leg out the other wire. now the SSR need a signal from the PID to work. on the SSR there is a + and a - which connects to the PID connections 7 & 8. this allows the PID to tell the SSR to turn on like a light switch and allow the power to flow. now the hot leg coming out of the SSR goes to the gas solenoid and the other blower speed controller. this way when the PID says hay we need more heat it turns on the SSR and that sends power to the gas valve and speed controller which puts the burner into high burn. now both wires coming from the speed controllers go to the last wire of the blower. and besides for connecting up the TC your should be good to go. its actually quite simple as long as you think it through and know what and how it is sapost to work. then just fallow the wires and connect accordingly. if you need any more help i would be glad to do what i can. remember in this kind of circuit you have 2 kinds of things. you have switches and loads. a switch can be put on a neutral or a hot leg and does not need the other one to work where a load needs a neutral and hot leg to function. The speed controllers are basically switches even though thy do use a bit of power to run and technically are considered kinda both but for this discussion we will call it a switch. but then look and the solenoid, its a load where it has to have both legs to run. good luck and let me know if you need any help.
 
Good explanation and run through, JT.

The second wire on the gas solenoid should be white ( in the drawing) and go to the neutral power buss.
Also, just in case you haven't installed one, you should mount the SSR on a heat sink.
Final note is that there should be a fuse in the red line immediately after the power switch. It should have a second fuse just before the PID,too. The MAIN fuse should be rated just above the maximum draw of the blower ,PID and gas solenoid combined, probably about 3 amps, so use a 250V-3 amp slow blow fuse. The PID fuse should be at the PID rating, which for your PID model is a 250V-1amp, slow blow fuse (see your instruction sheet, or look here: http://auberins.com/images/Manual/Manual version 3.4.pdf ).
I also assume that you have the two gas needle valves set up in a by-pass arrangement ( just like the blower pots) so one is turned on and off by the gas solenoid (HIGH) and the other runs all the time (LOW).

Otherwise, you are good to go.

You will love the control and smoothness of the operation of this setup. When I developed it, it seemed intuitive that the blower and gas be operated in a two stage mode, but I could find no reference to anyone having done it. The difference in cost between the one stage and two stage setup is probably less than $20. With proper settings on the PID and having the blower pots and needle valves carefully adjusted, you can hold a forge to +/- one or two degrees. I usually set mine at +/- 5 degrees.
Stacy.
 
Thanks, guys. I was hoping you two would chime in. I think I've got it now. Just need to run a white to the solenoid, and I'll be good to go to hook it all up.

Stacy, I am running two needle valves for the gas just as you suggested. The blower is a 165cfm forge blower, and it has a nice gate valve to control airflow beyond what the speed controllers will do. There is also a ball valve to quickly shut off the gas before the burner.

Thanks again for the help! I still have to finish lining the forge before I'm ready to test out the blower setup, and I'm waiting on a box to do that. I have the kaowool in, and I'll do the satanite in the next couple of days followed by the floor. Then it will be ready for the ITC-100 when it gets here.

Stacy, how far should the TC tube extend into the forge from the wall? Right now I've got it about 1.5" +/-.

--nathan
 
I didn't get into it earlier, but either now or later, put a gas solenoid at the main gas valve ( where you have the ball valve). just wire it to the black wire after the main fuse, and the white wire at the common buss. This will shut off the gas if there is a power failure ,or someone kicks the cord out of the wall socket.
Stacy
 
Not to hijack the thread, but Stacy did you get the master plan done. If my memory serves me correct you were designing one along this line, maybe. :)
 
I have "The Ultimate Controller" partially assembled. I ended up adding some features, and then things got so busy with work, so I set it aside until I get caught up. The basic functioning is the same as my original two-stage controller design. I had sent my plans to a forum member who was going to convert them to CAD drawings, but he never did it.
Most of the design changes are for a multi-burner controller. I managed to snag five 2" in-line blower fans ( ducted fans). They run on 28VDC, are fully controllable, and cost the government about $700 each.I bought them in England, for a song, from a military aircraft salvager, and had them sent over. Shipping cost more than the fans. These are the core of a new burner system for a gas HT oven. I'll hopefully get it together this winter and have it running when the weather turns warm.

Stacy
 
Stacy or anyone else...

I ran into a strange issue tonight after I got the gas side and solenoid wired up. Prior to wiring up the solenoid, I wasn't having any issues, but I only ran it for a little while when playing with the speed controllers. After I got the gas solenoid hooked up, I started having a strange issue that I think involves the speed controllers. Basically, the PID is working correctly and signaling the SSR when to turn on/off based on your temp setting, and the juice is being delivered to the high fan controller and the solenoid correctly.

However, I started having a strange cycling problem with the soldenoid when both speed controllers were on. It starts cycling rapidly (60Hz) when the speed controllers are set at certain positions (especially end ranges of high or low speed). BTW, this occurs not only when the SSR is on, but also when it is off. So it can't be from the power leg. My guess is that the cheap @$$ speed controllers are the issue, but I'm having trouble figuring out how. Could the controllers be shorted and somehow sending power down the neutral line to the controller? I'm at a loss.... The symptoms occur sporadically. Not every time, but when they do occur, they're consistant (i.e. usually with both controllers on and one of them at end range...changing the controller knob position tends to remove the cycling only to have it return when the knob is moved back; turning one of the controllers all the way off usually causes the cycling to stop).

I've gone over my wiring 10 times looking for anything that could be a short. I'm using wire nuts for the larger groupings of wires, and I've removed and re-set the nuts on every connection without change in the symptoms. I can't find anywhere that there could be a short between wires.

I'm going to head to Radio Shack tomorrow and pick up some better pots to try if they have them that handle 110V. I'm just thinking they're not up to snuff. If that doesn't work, I'm going to tear everything apart and rewire it all with soldered connections.

I have it all wired as suggested in the schematic above. The PID, solenoid, and motor are all connected to the same neutral wire. And the solenoid and the high-fan motor pot are connected to the same power coming off of the SSR.

I'll get a video up shortly that has the problem in it. Any ideas where this could be coming from?

Edit: Here's the video I took if it helps. It occurs at the end of the video:

http://www.youtube.com/watch?v=GtnVjxJ5U4U

--nathan
 
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mine does that to and i have not been able to find out why. i just make sure that the high burn speed controller is up higher then the pilot speed controller. i will like to see what stacy says about this as well.
 
JT, I got the video up. Is that similar to your problem? You can watch for the green light on the PID to tell when the SSR turns off at the end of the video, and that's when the problem occured (it also happens when the SSR is on at times). So it can't be from the power leg...it's got to be coming through the neutral let. Since the solenoid doesn't care which leg is hot and which is neutral, if it got enough current through the neutral leg, it might cause it to cycle....?

--nathan
 
silver_pilate said:
JT, I got the video up. Is that similar to your problem? You can watch for the green light on the PID to tell when the SSR turns off at the end of the video, and that's when the problem occured (it also happens when the SSR is on at times). So it can't be from the power leg...it's got to be coming through the neutral let. Since the solenoid doesn't care which leg is hot and which is neutral, if it got enough current through the neutral leg, it might cause it to cycle....?

--nathan
Click to expand...

i think the problem is with the 2 speed controllers connected togather. i think its creating some type of feedback. where is the video? i'm thinking of putting a relay between the 2 speed controllers so onley one can have power at a time.
 
It is feedback to the controller from the fan ( and perhaps each other). If you are using the solid state controllers ( like the ones in the photo) they need to be set to fairly close settings, or it may become unstable. I read that you fiddled with the internal trim pots on the controllers, so I think you may have changed the proportional control of that unit. If you have two controllers that you haven't messed with, try swapping them out. Or, you could try a bigger and better fan controller from the lighting section of the hardware store. I believe those ebay controls are actually made for lighting, and my be less than optimal for two-speed fan control. If using resistive control potentiometers (variac) or voltage control circuits, there should be no problem ( as long as the blower can be controlled by voltage). This is where a DC blower really shines.
Another thing that may be part of it is that the solid state controllers you have may not be compatible with all blower motors.

Another suggestion is a gate valve in the air line, which will allow both controllers to run at a higher setting, which may help (possibly back pressure related).

One change I made was bypass switches in the lines to each fan control and the gas solenoid ( PID-OFF-MANUAL). That way you can set each component independent of the other or the PID. (The unit I made originally had a two speed blower, so the low and high controller were both set in their upper range. Now, with the DC controllers that I have built for the new setup, the fans are voltage controlled, so I haven't eliminated this area of problem.)

On your setup:
Program the PID for a temperature about 200 degrees above the target ( this is temporary, for setting the burners).Turn off the PID.
Set the LOW first, balancing the LOW needle valve and the LOW controller to a flame that gives you a temperature about 50 degrees below the target. Run the burner for about five minutes, tweaking as needed to hold around this temp. Turn the HIGH fan control to about the same point on the dial, then energize the PID and set the high flame by balancing the HIGH needle valve and the HIGH fan controller. Set it so it reaches a temperature about 50 degrees above the target.
At this point you have set the two stages to run 50 degrees above and below the target, with a balanced atmosphere. This will mean that the fan will only be making a slight adjustment in speed between cycles. Hopefully this will solve the problem. Reprogram the PID for the target and try it out.

Plan B:
If you still has some sort of fight going on between the fan controllers, disconnect ( or switch off if you have a by-pass switch) the HIGH fan controller from the PID, and set the remaining (LOW) controller to balance the atmosphere correctly at about 50 degrees below the target setting. Set the HIGH gas setting as before. This will make the chamber have a small swing in atmosphere (very slightly more carburizing, as the solenoid delivers more gas in the HIGH cycles), but the flame will be constant, and the fan will run at one speed smoothly. You may barely even notice any change in the flame. This was my original design, and it worked well. I added the second fan controller to make the chamber atmosphere balanced all the time, but the difference is only slight, so you will be fine without the high fan controller. In the final design I may drop the two fan speed thing, as the difference is very slight.

Stacy
 
Good advice, Stacy. I will try better controllers first. The blower motor is an AC driven unit, but it's responded well to the cheap controllers I have.

Another thought I've had is to run the PID and the solenoid off of an entirely different power line. Keep things wired up the way they are, except run a seperate power line in to power the PID, and install a second SSR controlled from the same PID out to power the solenoid using the new line as it's power source and neutral. This will get the solenoid off of the same power/neutral as the blower controllers and motor and avoid any interference. Sound good?

--nathan
 
I switched out the two controllers for better quality fan controls, and the problem is better, but I was able to coax it to showing up again once. But like i said, much better. I took your advice, Stacy, and tried not to have the controls set too differently, and I've avoided the problem so far with the burner/blower running. I think you're right that it becomes too unstable with the controls at drastically different positions.

I'll really have to tune it up once the forge lining is done and I get the burner installed. Right now, I'm having to run it REALLY rich in order to sustain ignition in the open (just ran it that way to test it out, using the temp target on the PID to switch between high and low stages). I'm eager to see how it performs and how well I'm able to balance the two stages' atmospheres when it is installed in the forge.

Here's a video of it running in the open, with about 4 psi through the regulator, BTW (again, running really rich to sustain ignition):

http://www.youtube.com/watch?v=g5u0as_Oqlc

Thanks for the help!

--nathan

--nathan
 
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Nathan this is what i was talking about before. if you notice this relay will not allow both speed controllers to be on at the same time or even be connected. this will get rid of the feedback problem. when the PID is of the relay is switched to the low burn side. but once the PID turns on it switches on the high burn and switches off the low controller. I think this is the best way. i have noticed that even if the gas valve is not buzzing it gets very hot, i think this is because its getting current from the feedback. i will try this out and let you know. this is a cheep and easy part to get and would be easy to wire up. here is the revised wiring sketch and what the relay looks like and one place where its found.

Forge.jpg


NTE-R10-14A10-120.jpg


here is where its found, its only 12.95 you might be able to find something like this at radio shack as well.
http://shop.vetcosurplus.com/catalog/product_info.php?cPath=114_122_369&products_id=8874
 
JT and Nathan,
I considered the relay route. It would eliminate the problem as long as the problem isn't the fan controller. However, I would use an SSR not a magnetic coil relay. The continual cycling of this system would wear out the contacts before long.

I found that the difference in air volume for the LOW and HIGH settings was so slight that the second controller was really not necessary. Try it with only one controller and see if you like it better that way.

As I said before, the ultimate scenario was the use of a voltage controlled blower, either a brush type AC/DC motor, or a DC blower. These can be run with a small variac, or a simple voltage control circuit for lower voltage blowers ( LM317). If using a variac on a DC motor, add a bridge rectifier in the line to convert the AC to DC.

Other things to keep in mind when tuning a PID controller are to have enough hysteresis to prevent rapid cycling . If you set the cycle rate timing so it will allow a little time between cycles, set the range to at least +/-5 degrees ( +/- one degree will cycle on and off continuously), and tune the burner stages to be about +/- 50 degrees of the target, it will run very smooth. The PID will teach itself the parameters of the system, and become more stable after running a while,too. At startup, there may be larger swings in temperature and cycle times. As the PID learns it will slowly get closer and closer to the target by making smaller and smaller adjustments.

Stacy
 
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