How to convert a kiln from manual to digital

B

B Shafer

Member
I've had a manual kiln for a while now and it is kind of a pain in the butt to use so I finally made it digital. Here is how I did it with pictures so hopefully somebody else can take the digital plunge. The kiln I started off with was made by Satellite Mfg. I used the thermocouple that came with the kiln. To finish the project I bought a toggle switch from Home Depot,switch.jpg
a fan from Radio Shack
fan.jpg
a solid state relay and PID controller from lightobject.com,
pid.jpg
ssr.jpg
You will also need some wires and wire connectors.
 
Here is a nifty wiring diagram that I used for this project. http://img66.imageshack.us/img66/3059/hmgovenft5.jpg
wiring diagram..jpg
It does not show how to hook up the fan motor or the toggle switch.
After removing the manual control switch you have a power cord with black, white and green wires coming from it. The green wire is a ground and is mounted on the metal case. The black and white are your hot and neutral. You also have the wires coming from the heating element, as well as the thermocouple. The first thing I did was cut a hole in the side of the case to mount the cooling fan.
hole.jpg
I know, it's ugly. I haven't had time to make it look nice yet.
I also had to make a mount for the PID.
mounted.jpg
 
Next I hooked up the toggle switch. It goes on the black wire coming from the power cord on one terminal and the other terminal (the on position) has a wire going from the switch to the number 1 terminal on the PID and also a wire going to the cooling fan.
wire1.jpg
Next I ran the white wire from the power cord to the number 2 terminal of the PID. In the middle of this I put in a splice to hook up the other wire to the cooling fan.
wire 2.jpg
For the solid state relay I drilled holes to mount it but I hooked up the wires before actually mounting it. Did that make since? Same thing for the PID. I hooked all the wires up then mounted it in place.
Here is the solid state relay, mounted, with the wires hooked up. Note that it is mounted upside down in this picture.
wire 3.jpg
The picture shows ssr terminal 3 connected to PID terminal 6. Ssr terminal 4 to PID terminal 7. Ssr terminal 2 to one heating element wire. Ssr terminal 1 is connected to PID terminal 1. Remember, terminal 1 on the PID is also connected to the toggle switch.

Now here is what's going on with the PID.
wire 4.jpg
Terminal 1 has wires going to the ssr, terminal 1 and to the toggle switch. terminal 2 has a wire going from the power cord, and another wire going to the other heating element wire. Terminal 6 goes to ssr terminal 3. Terminal 7 goes to ssr terminal 4.
The thermocouple has a yellow and red wire. The yellow wire goes to the 9 terminal and the red goes to the 10 terminal.

And there you go. Get the toggle switch mounted,
mount switch.jpg
Mount the SSR and PID and you are all ready to go!
 
That is good information, it looks much easier than I thought it would be. Is the controller programmable?
 
Good move adding the fan. I have the same kiln and did the same thing (with some help from some relatives that know more about wiring than me), and it overheats the PID after not too long at stainless soaking temps. For now I'm aiming a hair dryer at the vents while it's on. It works, but it isn't elegant. I didn't realize it would be so easy to hook the fan up. One more thing to spend money on...
 
I have a handle on everything but the fan.
Looking for the fan, it occured to me that I had a choice between 120v and 240v. Will the 120v fan work or should I stick to the 240v ? I need the oven up and running tut suite. Normally I blaze ahead and find out the hard way, but with higher voltage there's too much potential to make this costly and dangerous.

Thanks,
Rudy
 
If I understand it correctly, the fan is only cooling the Solid State Relay. It doesn't need much airflow, so the fan power is minimal. Whichever voltage is least effort will work.

If you have the choice between 110V and 220V for the power feed to the elements, 220V is the better option. The heat generated across the SSR is dependent on the current passing through it. For a given power, the current (Amps) will halve if the voltage is doubled. The SSR will then only generate half the heat for you to get rid of.

Most SSRs are mounted on heatsinks and cooled by convection.

When they are mounted in small enclosures with limited air circulation (especially plastic enclosures, which tend to be good insulators) they often need help with the cooling.

Unfortunately, a definitive answer isn't really possible, as there are so many variables.

It is as well to think about where the cooling air comes from and goes to. If there's likely to be grinding dust about, you don't want to be directing it into your controller or SSR.
 
Thanks timgunn.
Good info. I realize now that the original post was based on 110v for the kiln. Mine is 240v. I should have followed my instincts about the fan voltage but even I have a limit for exercising stupidity. I did mount the SSR to a sizeable aluminum heat sink and the kiln works as is now, but I want the added cooling....... just in case.

Thanks,
Rudy
 
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