Finished my PID upgrade for my oven today

[scotner]

I bypassed the oven control, disconnected the broil element and installed the Mypin TA4 PID control. First time I fired it up it overshot by 25° or so and then settled back to the set point. I went back out today and started it up cold.Went up to 410° and settled at 400 to a couple of degrees above that. Next I opened the oven and threw in a tray with about 25 pounds of cold ingots. Temp dropped to 330° and was back up to 400° in less than 5 minutes. Held set point for 15 minutes after it stabilized. Hopefully I will not have to babysit this process all the way through now.

Also retained the kitchen timer feature and the oven light (such as it is).

[dikman]

Good , oven light is very important!

[Ausglock]

I like the timer with the light/buzzer.
temp is in Deg C
7 1/2 minutes to bake 2 trays of HITEK coated bullets 5Kg per load.

[scotner]

The light/buzzer on mine is a high temperature alarm. Since adding the PID control bypasses all of the oven controls there is no high limit thermostat in the circuit. SSRs are prone to fail closed which would result in the oven maxing out to whatever temperature the element is capable of reaching. My alarm is currently set at 450° F. If it goes off it is time to head to the breaker box.

I have a large mechanical relay that I plan to add as a safety shut off. I will install this in series with the SSR and operate it with the alarm output. Power to the heating element will go through a normally closed contact of the safety relay and operating the relay would open the circuit in the event of SSR failure.

[Ausglock]

I run 3 SSR's
one for each element and these 2 controlled by the third SSR.
This spreads the load and no SSR fails. Been using this oven for a few years now with no issues.

[nawagner]

The light/buzzer on mine is a high temperature alarm. Since adding the PID control bypasses all of the oven controls there is no high limit thermostat in the circuit. SSRs are prone to fail closed which would result in the oven maxing out to whatever temperature the element is capable of reaching. My alarm is currently set at 450° F. If it goes off it is time to head to the breaker box.

I have a large mechanical relay that I plan to add as a safety shut off. I will install this in series with the SSR and operate it with the alarm output. Power to the heating element will go through a normally closed contact of the safety relay and operating the relay would open the circuit in the event of SSR failure.

Check your controller. Some have a high temp shutoff, or at least they used when I used to do automation work.

[scotner]

I run 3 SSR's
one for each element and these 2 controlled by the third SSR.
This spreads the load and no SSR fails. Been using this oven for a few years now with no issues.

"No SSR fails" sounds pretty confident. Problem is you do not know if one has failed until both fail. One could be failed closed and the other one is controlling until it doesn't. Then you still have the same overheat problem. I would still prefer to have a mechanical safety relay in the circuit.

[scotner]

Check your controller. Some have a high temp shutoff, or at least they used when I used to do automation work.

It has an alarm feature which is a set of dry contacts that you can program to close at a set temperature. You can wire them to do whatever you can do with a set of NO contacts. That is why I have the audible alarm right now and plan to add the shutdown relay soon. I may add a latch circuit to this relay or possibly try to find a suitable latching or bistable relay instead.

[nawagner]

Sounds like you have a good plan to wire in the shutdown relay. Out of curiosity, did you tune the PID or let it do it's own auto tune? There's a whole science behind PID tuning.

[scotner]

Switched it to Farenheit, did away with the decimal point, set the high temp alarm and let it rock. I cured the first batch today with the new control. After I put the tray in the oven it took less than 5 minutes to come back up to 400°. After that it held +/- 3° the rest of the cure. I don't think I will tune anything if it keeps doing that. (I did run autotune on the PID for my Pro Melt).

[Ausglock]

The red LED's on the SSR's are visible through holes in the casing. I check them every startup to verify operation. High quality 40amp SSR's. Not cheap Chinese knockoffs.

[Humbo]

I have problems with my oven overshooting when getting back up to temperature after loading it with bullets. It typically overshoots by about 20 degrees C. I'm using Auber SYL-2362 PIDs, and have been trying to tweak the P, I and D settings to no avail. Any advice? Autotune doesn't seem to help.

[scotner]

Sorry, I didn't use auto tune and mine holds pretty close right out of the box. 20° C is a lot. Maybe some of the guys on here with more PID experience can help.

[Dragonheart]

Congrats on completing your oven it looks terrific. I might suggest installing a cooling fan for the relay. I use a salvaged fan from an old microwave and my relay stays at 90 degrees F under full load.
I used the auto tune and still have some overshoot, but since the substraight is still coming up to temp I don't see this as any problem as the temp stabilizes reasonably fast and stays within a couple of degrees.

[scotner]

Congrats on completing your oven it looks terrific. I might suggest installing a cooling fan for the relay. I use a salvaged fan from an old microwave and my relay stays at 90 degrees F under full load.
I used the auto tune and still have some overshoot, but since the substraight is still coming up to temp I don't see this as any problem as the temp stabilizes reasonably fast and stays within a couple of degrees.

There is a fan in the panel where all of the controls are located but I have not seen it run yet. I don't know whether it is bad or whatever controls it has not called for cooling yet. I will try wiring it direct to see if it works. If not, I have several replacements around. Thanks.

[Dragonheart]

There is a fan in the panel where all of the controls are located but I have not seen it run yet. I don't know whether it bad or whatever controls it has not called for cooling yet. I will try wiring it direct to see if it works. If not, I have several replacements around. Thanks.

My oven had a fan also, but since it was an all digital and I got it free because the control panel was out I wired in the lights and the fan to separate switches. I added the salvaged fan to the fan circuit so it would blow directly on the relay. I also added a separate timer that will control the PID when the timer is turned on.

[scotner]

My relay does not seem to build up much heat but I just checked it a couple of times during one cure cycle. It didn't really even feel warm then. Whenever I get around to adding the fan I will try to configure it to draw air directly across the fins of the heat sink. That should be the most efficient way to cool it.

The temperature got up to the low 50's today although breezy as all get out. I just had to go launch a few of my latest creations. Some in the 357 Sig pistols and now getting into cast PC 9's suppressed. Looks like both projects are going well. Will get back on coating and equipment when it is too cold to go play.