Solid State Controllers

[Suzanne Chudnoff]

For those of you using solid state controllers (including the solid state relays and connectors), can you give me some advice as to which controller to buy? I want to by one for various reasons. One is for better temperature control, controlling the elements separately (if possible), and because I've been told that they are very quiet. My kiln is in my living room, with vaulted ceilings and a porcelain floor. The clicking of the relay and connectors reverberates off the ceiling and walls and echoes throughout the entire house. Since my pieces are getting thicker and the schedules are longer, I don't want to be listening to this trying to go to sleep. I've been reading and researching, and the technical aspects are daunting. Electronics are not my strength, so I don't want to build one. I'd like to buy a plug and play. I've looked at Din-A-Mite and it's beyond my capability. I've looked at McCrayEZ2, and it seem rather kludge for a 46 amp (GlassGlow) kiln. The Digitry looks rather good and it looks like it's plug and play, but when I read the specs and look at the picture it doesn't say anything about a fan. From everything I've read, once you get over 40 amps, you need a fan. The controller would be mounted on the wall. Are there any other plug and play brands I should be looking at, or is Digitry the best solution? And is solid state going to be really quiet? I'd appreciate any help I can get. Thanks so much in advance.

[Morganica]

Check out Digitry. Very nice people, extremely helpful, and whenever I've called them they've been happy to work out something that suits whatever I need.

[Rick Wilton]

I agree with the digitry idea, you won't however be able to have zone controls as a plug and play unit. That would require rewiring the elements to separate relays and thermocouples.

I have three kilns running SSR's two of which are running more than 40amps neither has a fan on the controller nor the relays. The relays are rated at 50amps yet only have approx 20 amps running through each. If your relays are running close to the rating then a heat sink may be necessary. I don't have heat sinks on four relays, while I do have heat sinks on three others. I don't have any problems without the HS's. In fact I've never seen a kiln with a fan in the controller or electrical panel.

Yes they are quite as there is ZERO noise from the switching on and off. I like the quiet yet I know some people who get some "comfort" from the clicking.
Good luck

[Bert Weiss]

There are different kinds of solid state relays. They do not all use the same signal to turn on and off. The Watlow Dinamites are phase angle fired SCR's. They turn on or off 120 times a second. The result of this is a proportional amount of power being applied to the elements. This is easier on the elements, allowing for longer element life as well as tighter control. These relays require a 4 - 20 milliamp signal. Many controllers do not have this output. Digitry controllers can be configured with this output for a small charge. Bartlett and Orton can not.

There are also solid state elements that behave much like mechanical elements. These work on a 12vdc signal. Controllers designed for mechanical elements often use on/off signals that come several seconds apart. There are controllers that work with much shorter cycles. By the time you are down to a second or so, the result looks more like the SCR's.

Solid state relays are good for millions of cycles, whereas, mechanical relays are good for an average 100,000. The downside to solid state relays is that they are heat sensitive. They can not be mounted on the side of a hot kiln. If you lengthen your thermocouple wire, power wires, you can create a control board that is mounted on a wall. 18" away from the kiln.

About 15 years ago, I bought a set of used Watlow Dinamites for about $35 each. I have no clue how much they were used. I have had zero failures in this period of time. They all work well. Personally, if you have a controller with 4-20ma capability, I would rather have a used SCR than a new SSR, or any other relay I can afford. You can find these on Ebay. There is a catch. The serial numbers are long and complex. Each number or letter corresponds to a particular configuration. I have mistakenly bought the wrong ones. I bought ones configured for 480v single phase. I thought it meant up to 480v, but when I hooked it up, the heat output was very small. Then I found out why. I still own these, so if anybody has 480v power, contact me for some good relays.

I have often used a Continental solid state relay rated to somewhere between 50 and 75A. These can be used with Bartlett or other controllers with the 12v output. They must be mounted on an aluminum heat sink. Sometimes I have added a fuse to the system, but the fuse actually costs more than the relay to replace. They are a matter of convenience though, as they are much easier to replace and provide another easy on/off switch when you disengage the fuse.

[Al Bray]

There are different kinds of solid state relays. They do not all use the same signal to turn on and off. The Watlow Dinamites are phase angle fired SCR's. They turn on or off 120 times a second. The result of this is a proportional amount of power being applied to the elements. This is easier on the elements, allowing for longer element life as well as tighter control. These relays require a 4 - 20 milliamp signal. Many controllers do not have this output. Digitry controllers can be configured with this output for a small charge. Bartlett and Orton can not.

I don't want to stray to far from the post and let me say that I agree with many above that for an turn key solution from a controller manufacturer that is very familiar with the needs of Glass Artists, Digitry is at the top of the list.

But Bert I do have a question for you? Are you sure that all Watlow Din-A-Mite SCR power controllers "require" a 4 - 20 millamp control signal?

From my experience and from Watlows literature, the 4-20 milliamp input control signal is just one of several different input control signals options available for any given model of Din-A-Mite.

Reference http://watlow.com/downloads/en/specshee ... mc0113.pdf , Page six (ordering information, right hand column, Control section).

In my case I have a Watlow F4S (and just recently a Watlow F4D) with an Open Collector/DC output control module connected to a DC10-24C0-0000 (the C0 after the 24 indicating that this Din-A-Mite has a 4.5-32V DC input control).

In the F4S, I can set the control output to be fixed duration ON/OFF (as well as the duration of that ON/OFF cycle time), or I can set it to use something called Variable Burst (which is what I am using). .

Here is a document describing how it works and the benefits when used with resistive loads. https://www.watlow.com/downloads/en/whi ... output.pdf

Based on feed back from the thermocouple and the PID settings, the F4 figures out/varies the on/off cycles depending on the power draw of the resistive load (the elements) to maintain the firing profile/segement within a specified allowable deviation limit.

Of course, these on off cycles are totally silent, which took some getting use to because I was use to hearing the clicks and clatters of mechanical relays indicating the kiln was firing

I apologize in advance if I am missing something and completely wrong on this. It's just something that has always confused me when I see it stated that a Din-A-Mite SCRs require a 4-20 milliamp control signal and I am trying to understand the reasoning behind the statement.

- Al

[Bert Weiss]

Al, they come configured in many ways. The serial number is supposed to reveal the specs the device was designed for and with.

I am always looking for 4 - 20ma devices, so I didn't think much about other configurations. Each of the X's and O's n the serial number has some significance. I have called Watlow for help, and their tech line usually yields a knowledgeable, helpful, person.

[Suzanne Chudnoff]

Thank you all for the information. Bert, did you mean that I should order the proportional control for 4-20 milliamp current loop as an add-on option? Is there any way you can describe in simple terms what this means? Also, I don't understand what you mean by you'd rather have an SCR rather than a SSR. Are SCRs used rather than SSRs? Do they serve as a relay? I tried to find the answer on line but I don't understand electronic speak.

[Bert Weiss]

Thank you all for the information. Bert, did you mean that I should order the proportional control for 4-20 milliamp current loop as an add-on option? Is there any way you can describe in simple terms what this means? Also, I don't understand what you mean by you'd rather have an SCR rather than a SSR. Are SCRs used rather than SSRs? Do they serve as a relay? I tried to find the answer on line but I don't understand electronic speak.

SCR is a silicon controlled rectifier. It is a type of solid state relay SSR. There are different kinds of SCR's. Phase angle fired are the ones I use. I've also had zero fired.

When I have built kilns for others in the past, I used Continental SSR relays mounted on a heat sink, in conjunction with a Bartlett RTC 1000 controller that can handle 3 inputs and 3 relays. This is a simple, inexpensive setup, and it works. I just don't love the way it works.

One good alternative would be to phone Digitry and ask them to outline the difference in how the controller works with 12v verses 4-20ma control, and solid state verses mechanical relays.

Another alternative is to pick up used equipment on Ebay for reasonable prices.

[Al Bray]

For reference, I thought I would post a link to the following:

http://www.sdiohio.com/Pages/Power%20Control.htm

Though not totally free of techinical/geek speak, it is probably one of the easier to understand documents discussing the various type of power control, their advantages, disadvantages, etc.

[Suzanne Chudnoff]

Thank you Al! That was a great link. I hope to meet you when I come out to Michigan in July to visit Sue.