Here is my revision of the original post. The revision has to do only with the parts list and the way the pid works. The original PID I used basically had a relay in it that would switch AC current.
The second PID I bought did not work the same way. Instead of a relay, it actually output a 24 volts of DC current that can trigger an DA SSR (dc input/ac output). I have revised the parts list and wiring diagram to reflect this.
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First and foremost, Let me state I am not an electrician. I am not an engineer. Heck, I probably have no idea what I'm doing.
This project involves main voltage electricity and is dangerous.
I am not suggesting anybody do this, and I sure don't suggest you do this if you are not comfortable with projects that involve voltages and currents that could be very dangerous!
I am only posting this because some people were asking me to show how I put together my PID.
Got it? Don't do this. Don't try this at home!
That being said, Here we go.
I had decided that I wanted an electric smoker. I've had lots of grills, and lots of smokers, from charcoal to gas to wood fired. But I had recently gotten into sausage and jerky making, and I wanted a unit that would be very easy to use and control, and not have to worry about stoking with fuel. Don't get me wrong, I love my fire powered smokers, but I wanted something that would allow me to do things on weeknights and that could run all night and not need a whole lot of attention. To me, that spelled Electric.
So I got a
Masterbuilt Smoker from amazon for 149$ with free 2 day shipping, thanks to amazon prime. When I got it, I liked it, but found the analog thermostat to be a bit finicky to control. Sure, I could get it set, but it really took a bit of futzing with to get it to the temperature I wanted. Also, there would be fairly wide swings in temperature due to the nature of an analog thermostat.
An electric
thermostat operates by having one point where the heating element comes on, and another where it goes off. This can vary by quite a few degrees.
So I decided I wanted to use a
PID. A PID controller use an algortithm that allows it to 'predict' temperature fluctuations due to inputs, and can maintain a very fine control over the temperature.
So Here is the parts list.
Pid Controller 19$
SSR DA 20amp Relay 8$
Aluminum Heat Sink 5$
Type K thermocouple 7$
Enclosure (1/2" baltic Birch Scrap) 2$
Switch/Outlet Combo 3$
Misc Wire (10ga), Fasteners, DooDads 1$
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45$
Now I could have gotten the electronic version of the smoker, but I've heard different things about those control units, and I'm not 100% sure if they use a pid or not, anyhow, I had already purchased all of these items for another project I had in mind (
diy sous vide), and I just kind of re-purposed them.
Plus with this unit, It's kind of all purpose. I CAN use it for a sous vide controller if I want. It's completely stand alone. And if it breaks, I know how to fix it.
So Here is the basic wiring diagram. Your pid may/will not look exactly like this, but it should be similar. Be forewarned, some pids may use a relay to trigger the SSR, and some may output DC current to do so. It will also have a connection for the thermocouple. This connection may be configurable for different types of thermocouples that require different numbers of connectors.It may have additional switches that can be used for alarms/etc.
I'm using a standard household switch/outlet combo. I don't have them attached in this diagram for ease of understanding. These combo switches have a tab that connects the outlet to the switch. For this purpose, that tab will need to be removed.
The PID has a solid state relay built into it, but it's only capable of handling a small number of amps. In this case, the SSR on this pid can only handle 3 amps.
If I were to hook it up directly to the smoker, it would get fried. The smoker is rated to pull 12.5 amps. I tested it out last weekend and was able to get the empty smoker up to between 350 and 400. This amount of current requires using a seperate SSR. I chose to use a 20 amp SSR.
When running at low temps, i.e. 225, the power does not come on very often, or for very long. But when running at higher temperatures, it runs more often and longer. Due to the way
SSR's work, they can generate some heat of their own when they are switched on. To alleviate that, I chose to get an aluminum heat sink to attach to the SSR to help dissapate the heat. From my research, it could get to as high as 125 degrees. I have not tested this yet, so I do not know if that number is accurate or not. Once I run some more tests, I'll see if I can get some empriical data on what temp it can get to when it is running flat out.
Ok, So here is a picture of what I'm shooting for. PID on the front, Switch and outlet on the side. I used a Cat5 plug and jack for the thermocouple, but I'm not liking that design. On the actual build, I'll be swapping that out for something else. But this is functional, and it's mine, so it's what I'm using now.
Here are the basic parts, in their unassembled configuration, wires and screws not included.
Here is a detail of the thermocouple documentation. It has a switch for an alarm, the SSR, the power in, the attachments for the thermocouple, and that's about it.
Have you priced enclosures? Try and find something out there this size reasonably priced. Plastic, Metal, Eh, they all cost a bunch.
Nothing wrong with wood. So I grabbed a little baltic birch and got to work. On the back half of the box I put ventilation slots on the sides and top so that the SSR can cool down, if it needs to. This is what makes this marginally woodworkign related.