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jbruce

Geeks only - Raspberry PI controlled kiln

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27 minutes ago, neilestrick said:

I ran into a kiln like that once, where the previous repair guy had put a Bartlett controller on a Nabertherm and didn't do it right. I got a nice little shock when I tried to push an element in, even though the controller wasn't actually running. Luckily the teacher at the school had never gotten shocked. This is why two pole relays are used. Switching only one leg, the element won't heat up because the circuit loop isn't closed, but when you touch the element and ground it out you'll get hit.

@jbruce I'm also worried about the extension cord wires. Those wires are only rated for 12-20 amps, depending on the size of the cord. How did you arrive at it being large enough for 4 times the 40 amps? And if the kiln pulls 40 amps, the wires should be rated for 50 amps, which means you should have 6 gauge wire in there.

I think he's using all three conductors in each extension cord as a single conductor

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So what's the solution to the single ssr?  Two separate ssrs connected to the rpi?  Does the rpi have two outputs to trigger the ssrs?

I looked at 2 pole ssrs and they're nutty expensive, used in HVAC it looks like

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1 hour ago, Bill Kielb said:

Parallel feeder idea, not skookum or good practice.

I wasn't aware of this practice before now. After reading up on it, I know why- it's only allowed by code for wires over 1/0, which I've never dealt with. And even then there are a ton of rules. Some potential safety issues with that method.

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5 hours ago, liambesaw said:

So what's the solution to the single ssr?  Two separate ssrs connected to the rpi?  Does the rpi have two outputs to trigger the ssrs?

I looked at 2 pole ssrs and they're nutty expensive, used in HVAC it looks like

Single SSR and the power disabled by relay is the norm. Actually it’s common to see the existing relays stay in place and feed the SSR. The relays are driven by a safety output so once the program is run they are latched closed for the entire firing and the SSR’s are switched on and off by the controller. Often the existing relays are safety looped through a lid switch as well.

the end result: lid closed + no controller errors + program start pulls in all the regular relays which then provide power to the elements and SSR’s. As long as no errors and the lid is closed these relays stay closed and the computer controller is free to cycle the SSRs to heat the kiln. 

SSRs often fail shorted as much as open so it is absolutely necessary to have another way to disconnect them from the load. A new device design often has a main contactor that disconnects all power incorporated into its safety loop design. SSRs are heat and overload sensitive so it is absolutely necessary to heatsink them to 2C/W or less and install fast blow fuse protection properly sized to the SSR.

interesting tidbits on SSRs, they are starting to make them with current sensors built in. The relevance? An SSR controlled kiln with these could also display the amperage of each element as it is operating. Really cool diagnostic tool!

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4 hours ago, neilestrick said:

I wasn't aware of this practice before now. After reading up on it, I know why- it's only allowed by code for wires over 1/0, which I've never dealt with. And even then there are a ton of rules. Some potential safety issues with that method.

Yes, it is common for higher amperage services where 4” pipe is the raceway limitation so Parallel feeders is the only practical way to do this economically using multiple network sets to get to the desired service amperage and often a secondary set (s) as backup for critical loads / structures.

an extension cord used in this way is not good practice, nor generally code compliant in any way. 

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5 hours ago, Bill Kielb said:

Single SSR and the power disabled by relay is the norm. Actually it’s common to see the existing relays stay in place and feed the SSR. The relays are driven by a safety output so once the program is run they are latched closed for the entire firing and the SSR’s are switched on and off by the controller. Often the existing relays are safety looped through a lid switch as well.

the end result: lid closed + no controller errors + program start pulls in all the regular relays which then provide power to the elements and SSR’s. As long as no errors and the lid is closed these relays stay closed and the computer controller is free to cycle the SSRs to heat the kiln. 

SSRs often fail shorted as much as open so it is absolutely necessary to have another way to disconnect them from the load. A new device design often has a main contactor that disconnects all power incorporated into its safety loop design. SSRs are heat and overload sensitive so it is absolutely necessary to heatsink them to 2C/W or less and install fast blow fuse protection properly sized to the SSR.

interesting tidbits on SSRs, they are starting to make them with current sensors built in. The relevance? An SSR controlled kiln with these could also display the amperage of each element as it is operating. Really cool diagnostic tool!

That's how Nabertherm wires their kilns- one big main mechanical relay coming off the controller safety output, and SSRs cycling the elements. Most brands have not switched to SSRs because it's a more expensive setup than just using mechanical relays, and it would require a redesign of the control box layout to fit everything. That plus most customers don't care enough about it to justify the price increase. I know Skutt has a prototype out there somewhere, and L&L has considered making it an available option. I know they've used them on customs kilns before.

Good thread.

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I want to make sure I answer all of the points.  First question is about using extension cords. The conductors are 12 gauge and according to

https://www.powerstream.com/Wire_Size.htm

for short runs / chasis wiring, a single 12 gauge conductor can handle 41 amps.  I am using three conductors for each connection. Experimentally with all elements running 100% of the time, the conductors are not getting warm.  Even if it can only safely handle 60A, that is 20A above the max for the kiln and 10A above the breaker it is plugged into. So is using this wire dangerous, or just messy and something you'd never consider for a consumer product?

Next point is about fuse protection for the SSR. What would you rate the fuse at? 50A? There is a 50A breaker box that the controller plugs into, so do I still need the fuse?  Yes, if I was making a product for sale, I'd have one.

Next point is about the heatsink being inverted and connected externally.  Not sure about the inversion because when I received it, this is how it was oriented / mounted to the SSR.  Yes, the heatsink is connected externally.  There is thermal paste between the SSR, the bud box, and the bud box and the heatsink.  My intent here was to have the bud box help in cooling.  Experimentally when all elements are on 100% of the time for a long period of time, the heatsink is warm to the touch and the bud box is a little cooler than the heatsink.

Next question, is there a constant 120V to the elements of the kiln? Yes there is.  I have only a single SSR switching a single leg.  I have a breaker box just behind my kiln and I shut that off before I open the kiln.  This problem is easily solved by using 2 SSRs or a

https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=331

which is essentially 3 SSRs in one.  When I first built this prototype I used two 30A SSRs.  They were not zero crossing SSRs and so they did not switch at the same time.  This caused an inrush current through one of the SSRs that exceeded it's rating and POOF.  That is when I switched to using a single SSR with a 50A rating.  At the time I could find no resources to definitively tell me how to best handle switching.

I'm open to suggestions - especially when it comes to safety.  I am open to modifying docs so folks who choose to build do so safely.

 

Edited by jbruce

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Only thing i can think of, is that with 3 separate insulated strands, that's 3 points of failure per connection.  What if one wire has some broken strands and higher resistance?   I'm attaching the NEC wire ampacity chart for your future reference.

Also in this case, #6 copper wire is cheaper than cannibalizing an extension cord, 

 

 

NEC-Ampacity-table.jpg

Edited by liambesaw

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29 minutes ago, jbruce said:

I want to make sure I answer all of the points.  First question is about using extension cords. The conductors are 12 gauge and according to

https://www.powerstream.com/Wire_Size.htm

for short runs / chasis wiring, a single 12 gauge conductor can handle 41 amps.  I am using three conductors for each connection. Experimentally with all elements running 100% of the time, the conductors are not getting warm.  Even if it can only safely handle 60A, that is 20A above the max for the kiln and 10A above the breaker it is plugged into. So is using this wire dangerous, or just messy and something you'd never consider for a consumer product?

Next point is about fuse protection for the SSR. What would you rate the fuse at? 50A? There is a 50A breaker box that the controller plugs into, so do I still need the fuse?  Yes, if I was making a product for sale, I'd have one.

Next point is about the heatsink being inverted and connected externally.  Not sure about the inversion because when I received it, this is how it was oriented / mounted to the SSR.  Yes, the heatsink is connected externally.  There is thermal paste between the SSR, the bud box, and the bud box and the heatsink.  My intent here was to have the bud box help in cooling.  Experimentally when all elements are on 100% of the time for a long period of time, the heatsink is warm to the touch and the bud box is a little cooler than the heatsink.

Next question, is there a constant 120V to the elements of the kiln? Yes there is.  I have only a single SSR switching a single leg.  I have a breaker box just behind my kiln and I shut that off before I open the kiln.  This problem is easily solved by using 2 SSRs or a

https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=331

which is essentially 3 SSRs in one.  When I first built this prototype I used two 30A SSRs.  They were not zero crossing SSRs and so they did not switch at the same time.  This caused an inrush current through one of the SSRs that exceeded it's rating and POOF.  That is when I switched to using a single SSR with a 50A rating.  At the time I could find no resources to definitively tell me how to best handle switching.

I'm open to suggestions - especially when it comes to safety.  I am open to modifying docs so folks who choose to build do so safely.

 

As  I said this is still a nice project

and it is not worth the time to talk about why extension cords are not used as a single conductor or whether a fuse is way faster than your breaker and highly suggested by SSR folks or why mounting the heat sink outside was necessary when designed for direct mount  with a saddle for the SSR and thermal calculations that clearly show this in not desireable, or why we didn’t criticize the raw hole drilled for the wires without grommet or any number of things in a beta stage project. That anyone would seek to defend these issues without saying simply it’s  not a finished project is a bit troubling in my view.

again it’s a nice project and if you produce it for others you need to step up your game a whole bunch, none of that will fly as code or be approved for many reasons, none of which entail reading a chart and not understanding the application of or the proper way to derate things.

I am not here to argue the obvious, it is not code or UL or CSA or FM,  and won’t be in its present form. So last thing to say It’s in a great stage and has performed well. Hats off to your hard work and wonderful success, I believe it’s important to encourage, but the reality of needing to now make it industry standard and as safe as practical is your next step in your own development.

just my opinion so take it for what it’s worth but I have a lifetime of working through these types of issues.

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 I agree that this is a great thread. No denying that seeing someone build their own controller is very cool. But I do have a responsibility as a moderator to point out things that could be dangerous to others who would copy what's being done here (it's actually in the rules), and for the safety of the person posting. I don't know when a member isn't aware of the safety issues, or is just working through it fully aware that the final product will be done differently. Either way, I think it's good for things to be discussed, for the education and safety and knowledge of everyone involved. I don't think any of it diminishes the value and hard work of what's being done. In fact, I feel like to adds to the project, because it fleshes it out more. As I said before, I wasn't aware of the parallel feeder method, so I have learned something, too.

So on that note,  I have seen the charts for chassis wiring, and I don't think what you have there qualifies, because those cords are power wires, not chassis wires. Chassis wires are very short single wires connecting parts within the appliance, which are not bundled and therefore can dissipate heat well. What you've got there are power transmission wires, which require a much larger gauge and can be bundled. The chart that Liam posted is a good one to go by. If you look at all the wire gauges recommended by the kiln companies, they go with the 60C column because it doesn't hurt to be on the conservative side.

The danger of using them as a parallel system is that if any of the wires in a bundle comes loose, the others will be overloaded and overheat. There are a lot of rules about how parallel systems must be installed because of that, and they're limited to use in very high amperage systems where it's impractical to use large single wires. It's a code thing, not a personal preference. The fact that they're not overheating means that they are, in fact, performing as a parallel system should, but that doesn't mean it's safe.

The prototype Skutt SSR kiln I saw had a big heat baffle mounted to the front of the control box just like yours.  And their control box was mounted on the kiln. So it seems you're definitely on the right track there.

You don't necessarily have to have a fuse in the system, since it's under 50 amps. Once you get over 50 amps you have to have branch fusing in the system. It's another reason production kilns are more expensive than hobby kilns of the same size. More parts, more engineering.  Definitely have a fuse on the controller path, but you don't have to have one on the power path. If you do decide to put one in, size it with the breaker.

I would put in a mechanical safety relay to kill the whole system in the event of an SSR fusing 'on'.

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25 minutes ago, neilestrick said:

 I agree that this is a great thread. No denying that seeing someone build their own controller is very cool. But I do have a responsibility as a moderator to point out things that could be dangerous to others who would copy what's being done here (it's actually in the rules), and for the safety of the person posting. I don't know when a member isn't aware of the safety issues, or is just working through it fully aware that the final product will be done differently. Either way, I think it's good for things to be discussed, for the education and safety and knowledge of everyone involved. I don't think any of it diminishes the value and hard work of what's being done. In fact, I feel like to adds to the project, because it fleshes it out more. As I said before, I wasn't aware of the parallel feeder method, so I have learned something, too.

So on that note,  I have seen the charts for chassis wiring, and I don't think what you have there qualifies, because those cords are power wires, not chassis wires. Chassis wires are very short single wires connecting parts within the appliance, which are not bundled and therefore can dissipate heat well. What you've got there are power transmission wires, which require a much larger gauge and can be bundled. The chart that Liam posted is a good one to go by. If you look at all the wire gauges recommended by the kiln companies, they go with the 60C column because it doesn't hurt to be on the conservative side.

The danger of using them as a parallel system is that if any of the wires in a bundle comes loose, the others will be overloaded and overheat. There are a lot of rules about how parallel systems must be installed because of that, and they're limited to use in very high amperage systems where it's impractical to use large single wires. It's a code thing, not a personal preference. The fact that they're not overheating means that they are, in fact, performing as a parallel system should, but that doesn't mean it's safe.

The prototype Skutt SSR kiln I saw had a big heat baffle mounted to the front of the control box just like yours.  And their control box was mounted on the kiln. So it seems you're definitely on the right track there.

You don't necessarily have to have a fuse in the system, since it's under 50 amps. Once you get over 50 amps you have to have branch fusing in the system. It's another reason production kilns are more expensive than hobby kilns of the same size. More parts, more engineering.  Definitely have a fuse on the controller path, but you don't have to have one on the power path. If you do decide to put one in, size it with the breaker.

I would put in a mechanical safety relay to kill the whole system in the event of an SSR fusing 'on'.

Good thread, good info, still a nice project but there are many things in the world more complicated than googling and reading tables and trying your best to understand the basis.

As a last note, SSR’s fail quickly under short circuit. Much quicker than a circuit breaker will trip and often quicker than a standard fuse will protect. The manufactures provide the appropriate amps squared seconds rating  to protect their device. I should have been more clear, the fuse is intended to protect the SSR and all manufactures provide data and the appropriate fuse to use so your SSR will have a long useful life.

I definitely did not intend the SSR protection to fall into the machine protection required line of thinking. They are different and I should have been clearer.

75BB9E84-08F2-4585-9288-3B2E16E32E32.jpeg

Edited by Bill Kielb

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Please understand that this is just an interesting project / experiment. Please note that I have no intentions of creating a product.  Please understand that this hardware is not finished and is in an alpha state.  I do not want defend improper practices and I am here to learn from others and improve.

I love that I have found a passionate, intelligent, experienced group of people in this forum.  If I had a forum with information like this when I started the project, it would have changed the course of the project.  So now, I'm left to make things right with folks so they don't follow the wrong path.  Please help me do that.

1. Conductors on the input side need to be to code (could I use a replacement 50A dryer cable for this?)

2. Grommets for any conductor that goes into the bud box

3. connect the heatsink directly to the SSR (can I then mount the heatsink to the bud box?)

4. use an Ultra Fast Acting fuse at the rated amperage of the circuit to protect each of the SSRs - 50A

5. use an SSR on each leg, instead of just one

6. use mechanical safety relay to disable all SSRs in the event there is an SSR failure/short.  I'm not at all sure how to implement this.  Can someone post a link to a schematic?

 

Did I leave anything out?

Edited by jbruce

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 @neilestrick The controller is a raspberry pi 3. It uses standard power supply which is 110V input, 5.1VDC 1A output.  This connects to a micro usb port on pi.  The power for the controller needs to be separate from kiln power.  The controller is used to monitor the temperature even when the kiln is off.  The power code for this currently dangles out of a gaping hole in the front of the bud box.  This needs to be fixed.

The load side of the relay is 48V-280V AC 50A.  I believe I need another one of these to bring the controller up to snuff.

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5 hours ago, jbruce said:

Please understand that this is just an interesting project / experiment. Please note that I have no intentions of creating a product.  Please understand that this hardware is not finished and is in an alpha state.  I do not want defend improper practices and I am here to learn from others and improve.

I love that I have found a passionate, intelligent, experienced group of people in this forum.  If I had a forum with information like this when I started the project, it would have changed the course of the project.  So now, I'm left to make things right with folks so they don't follow the wrong path.  Please help me do that.

1. Conductors on the input side need to be to code (could I use a replacement 50A dryer cable for this?)

2. Grommets for any conductor that goes into the bud box

3. connect the heatsink directly to the SSR (can I then mount the heatsink to the bud box?)

4. use an Ultra Fast Acting fuse at the rated amperage of the circuit to protect each of the SSRs - 50A

5. use an SSR on each leg, instead of just one

6. use mechanical safety relay to disable all SSRs in the event there is an SSR failure/short.  I'm not at all sure how to implement this.  Can someone post a link to a schematic?

 

Did I leave anything out?

Most of these issues go away when this moves from alpha to beta.

conductors will likely change when you make this into a fixture wire project as long as you are dead set on the temporary extension cord approach. Grommets will likely not be needed again as this gets packaged for permanence not as a development project. The heatsink design is a bit more difficult but I have a retrofit that I am going to try that solves this for me. It entails using production linear heatsink material (very inexpensive) designed at about 1.8C/W or you simply would make the final version bigger and stick this on the inside, vertical with ventilation holes which would reduce its effectiveness. Fast acting fuse to protect your SSR,  single SSR is fine, solid safety relay protection is all that is necessary. Most kilns use double pole relays for a reason. Whether the double pole relay would be sufficient as a disconnect is the overriding question here or is a definite purpose contactor necessary.

i think a lot of this goes away as you look to incorporate the design into something permanent. Now that you are thinking of these things it’s half the battle.

I expect to try and do a retrofit SSR on an existing kiln within a month or so. I will post some of the choices we make and why and see if I can make it easy and safe. Not sure how this will go though so we are moving slow and gathering data and requirements.

 

its still a wonderful project

Edited by Bill Kielb

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One point I saw when looking at SSR paperwork is that they require active cooling if run at 30 amps or higher, maybe a cpu cooler would be a cheap option, I used those with some high wattage cob LED units a while back and they worked great.  Seems the SSRs have similar cooling requirements as a cpu. Can also be powered via the rpis USB hub

Edited by liambesaw

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Most of the curves I have viewed show 1.8C/W cooling works fine. Ambient air at 80-90 degrees means a 4” X 4” X 1-1/2” parallel fin exchanger is likely fine. Powered cooling is a solution to shrink the form factor but also relies on another mechanical device. Doing it with convection if reasonable is probably most dependable.

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2 minutes ago, Bill Kielb said:

Most of the curves I have viewed show 1.8C/W cooling works fine. Ambient air at 80-90 degrees means a 4” X 4” X 1-1/2” parallel fin exchanger is likely fine. Powered cooling is a solution to shrink the form factor but also relies on another mechanical device. Doing it with convection if reasonable is probably most dependable.

Active probably better if it's contained in a kit box right?  I'm trying to think of ways to not have a hot heat sink inside of a kit box, it might affect the efficiency of the heatsink.

Just tossing out ideas at the moment

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I agree, my present thought for adding to an existing kiln is to mount a flat parallel  exchanger on the outside of an existing kiln  control box. Cut completely through the box behind the exchanger and direct mount the SSR to it.  Exchanger on the outside, SSRs on the inside but still directly connected to the heatsink. Heatsink vertical for best performance out where the ambient temperature is relatively cool.

just an  idea so far though with a little research. Have not done any calcs yet or tests. Heat sinks are pretty economical actually. As a one time cost this may be a way to go in retrofit.7A471A8A-8147-4B09-B33B-A0FC617D7680.png.0c8f9d926d492405fbafa1f6c58595c9.png

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4 minutes ago, jbruce said:

 @neilestrick The controller is a raspberry pi 3. It uses standard power supply which is 110V input, 5.1VDC 1A output.  This connects to a micro usb port on pi.  The power for the controller needs to be separate from kiln power.  The controller is used to monitor the temperature even when the kiln is off.  The power code for this currently dangles out of a gaping hole in the front of the bud box.  This needs to be fixed.

The load side of the relay is 48V-280V AC 50A.  I believe I need another one of these to bring the controller up to snuff.

Thank you. I've never used one of those, so I wasn't sure how it was powered.

To clean up the box:

1. Replace the power cord with a 6ga 3 wire cord. You can reuse the plug, just get a new cord. I buy the SEOW cords from McMaster, about $35 for a 10ft length. They're super flexible and easy to work with. Use a cord grip, or just a simple clamping cable connector to hold the cord securely in the hole in the box. Use a snap-in plastic grommet to hold the TC wire, and another for the controller power supply. You'll have to figure out which sizes you need for each cable. They not only protect the cord from the sharp edge of the hole, but keep the cord from pulling out if you accidentally snag it.

2. You can go with the single leg SSR if you add in a mechanical main relay. Every kiln system I've seen uses a definite purpose contactor (DPST-NO) for the main. Because it is big and your controller has low voltage output, you'll need an intermediate relay (pilot relay) between the controller and contactor. So for the pilot relay you'll need something that has a coil that will work with your controller, either single or double pole. L&L uses their standard 25 amp 2 pole 12VDC coil relays for the pilot. In the Skutt KM-1 external controller, they use a small single pole relay and just run the power for the other side of the coil directly off the main power. I've attached a wiring diagram of the KM-1 which should give you a good idea of how you can do yours. Either way works. The contactor, then,  will need a 240 volt coil. You'll have to set up your programming to turn the main relay on and keep it on when the kiln is firing, and off if there are any error situations, or at the end of the firing. The most important error would be to shut it down if the temp is climbing too quickly, which would indicate a stuck relay or TC issue.

3. Make sure you ground the box.

4. If this was my project, I would use a larger box so it's easy to work in, put in a terminal strip where the main power comes in, and distribute everything as needed from there. It'll make the wiring much simpler to deal with, and easier to see what's going on. Terminal connections are much easier and cleaner than wire nuts.

I think we're all on the same page here. You've got the thing working, which was the hard part (congrats!), now it just needs cleanup and safety concerns addressed, which is mostly just busy work. It's a great project.

@liambesaw I had a small test kiln last year that got really hot during firings. Because the kiln and box were only about 10 inches tall, there wasn't enough draft created in the box to keep it cool like it would in a taller kiln. The controller was getting very close to its max operating temp. So I installed a little computer fan in the bottom of the box, and it made a huge difference. I agree with @Bill Kielb that it would be good to avoid adding in more parts, but it will definitely work if it comes to that.

I've also attached a pic of a Skutt with SSRs. You can see the big cooling fins on the box.

KM-1 Wiring Diagram.jpg

GM-818-3CR_cap.jpg

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14 hours ago, neilestrick said:

 I agree that this is a great thread. No denying that seeing someone build their own controller is very cool. But I do have a responsibility as a moderator to point out things that could be dangerous to others who would copy what's being done here (it's actually in the rules), and for the safety of the person posting.

The only rule I can find says information is presented at your own risk.

On 3/11/2014 at 5:49 PM, Jennifer Harnetty said:

All information is presented as is, and your reliance on any information presented on this site or its forums is at your own risk. Although Ceramic Publications Company may monitor discussions, postings and other user generated content from time to time, we are under no obligation to review material on the web site, and you agree to hold us harmless from any actions based on content that you post or read on these sites.

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@High Bridge Pottery, part of the duties of a moderator is to give warnings when unsafe practices are being posted. Our roles are not outlined in the Terms of Use but we have an additional private set of Moderator Guidelines we are asked to adhere to.

 

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@High Bridge Pottery Are you deciding if you should turn the relay off or on every 2 seconds?

Yes.  This is a configurable parameter. The code originally made this decision every .5s and that duty cycle was too high for kilns.  I have heard some folks going as high as 10s.  Since it is configurable, you decide the value that works best for your kiln.

How did you come up with the PID values to use?

I read many articles discussing PID tuning.  Some were complex algorithms, some simple.  I tried to find the simplest method that could be done in a few hours.  The process I used is described here... https://github.com/jbruce12000/kiln-controller/blob/master/docs/pid_tuning.md

The tuning it provided the first time around is good for my use.  If you find a simpler, better tact, post a PR and I'll check it out.

Part of our duties...

@Min

@neilestrick @Bill Kielb

If you, Neil, or Bill feel like this has become too big a risk to remain on the site, I totally understand. The last thing I want is for anyone to violate local code or endanger themselves.  I am committed to improving my implementation, but it will take time.  I have a full time job and this is a side project / experiment for me.

I cannot stress enough the value I have found in this forum.  I thought I was pretty good at what I was doing.  Turns out, I made lots of mistakes.  If I made these mistakes, others will too.  I think if folks had a resource where they could learn these things, it could prevent folks going down the same road I have.

Not sure what else to say on this topic.  Assumptions can be dangerous.  Reflect carefully on risks others point out.  Strive to become better.

Edited by jbruce

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