Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
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- Aug 20, 2004
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In an effort to help those who are challenged by trying to connect a PID and its associated circuitry to a device, I will give the procedure and setup to run a toaster oven as a tempering oven. The same hookup can run a variety of things (solenoid valve on a forge, salt pot, BBQ smoker, kiln, etc.), with the appropriate thermocouple and SSR. If you only want it to read temperature, you just use the thermocouple as a thermometer.
Some components can be found in thrift stores, other from online suppliers, and most everything can be purchased on Amazon or Ebay. Search for PID, Thermocouple K, SSR, Thermocouple plug connector, 120V cooling fan.
The Oven:
Any manual control toaster oven will do fine. You don't want a digital control oven. One of the old twist-dial types for a few dollars from a thrift store will be perfect. It only needs to be able to set the oven on HIGH or ON. You are going to permanently set it on the highest setting. It needs nothing modified beyond a small hole drilled to allow the thermocouple to stick inside. Some folks wrap a blanket of insulation around the oven to get a little more efficiency. That is a good idea but use the proper insulation. You want a jacket insulation blanket, which controls the loose fibers, like a water heater wrap from the hardware or plumbing shop. Wrap the entire toaster, including the back, and tape the jacket with duct tape. Leave a flap to drop over the front door. This will greatly help the oven regulate temperature and hold a somewhat higher temperature.
The PID:
Most cheap PID controllers are pretty much the same. You want 120VAC input and the ability to take a type K thermocouple.
They often come as a package deal with the PID, SSR, heat sink, Thermocouple, and wires.
Amazon search - PID Temperature Controller Set, PID Temperature Controllers Thermostat Regulator, SSR 40DA Solid State Relay AC 100 to 240V, White Heat Sink and K Type Sensor Thermocouple
The Thermocouple:
The Thermocouple that they often give you with those controllers is pretty useless for most of our purposes, so you will likely need a new one. The temperature range needs to match the desired use. If it is going into an electric toaster oven, it just needs to be a type K that is long enough and rated around 1000F. (BTW, there is a + and - wire, make sure you hook them up right or the display will read wrong.) If your TC has a plug-in probe cord. get a corresponding K-type socket to connect to the PID.
You don't want the ceramic coated TCs for a tempering oven. Just a metal clad probe.
Amazon search - 3M K-Type Thermocouple 100mm Sensor Probe Temperature From -100°C to 1250°C
How it works:
The SSR is actuated by the DC output voltage from the SSR control circuit on the PID.
The SSR can control 48-480VAC circuits. The SSR amperage rating needs to be enough to run the device being controlled, plus a bit. Most folks just use a 40-Amp SSR. You will need a heat sink on the SSR to keep it from burning out (they only will take 3-5 amps otherwise). A small fan, like from a computer, should be used to cool the heat sink.
A 10-foot 120VAC 15-Amp rated 14-gauge extension cord. It will be cut into four pieces - 3-feet with female socket; 5-feet with the male plug; two 1-foot pieces for connector wires. Strip 6" of the outer insulation off the longer pieces and all the outer insulation off the foot long piece. Strip 1/2" off all the ends to expose bare wire.
Other parts - Some connector strips/blocks or wire nuts,18-gauge wire, a power switch, a 15-amp buss fuse and holder, some miscellaneous parts and screws.
To hook all this up:
Enclosure:
Select or make a suitable cabinet for the controller. While you could mount it all on a flat board, open circuitry with 120VAC is a bad idea. A piece of 1/4" plywood with a plastic bread storage container on the back side to cover the wires will work if you don't want anything fancier.
The PID -
Mount the PID on the board/cabinet. Yours may have come with a case or mounting plate of some sort, so mount it as needed.
Connect the thermocouple to the + and - contact screws. Be sure to observe the polarity of the probe! You may need to use a socket that matches the cord type.
Connect two of the 12" long 14-gauge wires to the AC POWER screws. One should be blacks and the other white (from the extension cord). If the PID has a ground terminal, connect a green wire there.
Connect two 12" long 18-gauge wires to the DC SSR Control screws. They are + and - so it is best to use red and black wires.
There may be some additional jumper wires or clips to connect on the PID as the directions will tell you.
On the SSR:
Mount the SSR on the heat sink as described in its instructions (it may recommend using heat sink compound, which is a good idea). Make sure the cabinet or enclosure has sufficient room to aid cooling.
Connect the red/black wires from the PID to the corresponding+/- DC CONTROL contacts on the SSR.
Connect the black AC wire on the female piece of extension cord to one of the LOAD contacts on the SSR. Connect a 12" long 14-gauge black AC wire to the other LOAD contact.
Mount the SSR, heat sink, and the fan so the air blows through the fins and cools the SSR.
The fan connects to the 120VAC buss strips. (see POWER below)
POWER:
Take the 10-foot extension cord and cut it into four pieces as described in the parts list. There will be a common wire (white) and a load wire(black) and a ground wire (green). This will become the power-in and power-out cords and connection wires.
There will be several things connected to these cords, so installing two power buss/multi-connection strips is simplest and safest, but wire nuts will work. AC connection wires will be white and black. Securely fasten the male and female power cord pieces to the cabinet with cable clamps of some fashion.
Install a SPST power switch and a 15 amp fuse. Connect the black wire from the male power cord (the 6-foot-long piece with a plug) to the switch and the switch to the fuse.
Install a black AC wire from the fuse to the load power buss. At this buss the connections are made to:
The 12" black wires from: The load contact on the SSR: The PID: and The fan.
The white wire from the power cord goes to a common buss at which the connections are made to:
The white wire on the Female power cord end (3-foot piece with a socket): The PID: The fan.
The green wires are connected together.
The toaster oven (or controlled device) plugs into the female cord. The male cord will plug into the wall socket.
Insert the thermocouple into the oven chamber. Affix as needed. If the thermocouple is installed just below the rack/grate/shelf, it can be affixed with a twist of bare wire. That way it reads the temperature close to the blade being tempered. Simplest way of installing is drilling a hole in the back or side and sticking the TC through.
You only want the metal probe in the oven, not its wires. Use a longer probe if needed for larger ovens. The tip of the probe is what reads the temperature, so as long as the tip is where the knife will sit on the rack, it will be fine.
The operation of the PID is simple and the instructions give the setup and programming. A good supplier will offer support help. The basic operation is to set the desired temperature (set point or set value) and turn the control program on. The toaster oven is permanently set at its highest setting and will be turned on and off by the controller and the power switch. The controller will allow the power to flow to the oven until the temperature is reached. Then it will cycle on and off to maintain that setting. The PID will auto tune itself to learn how to hold the temperature evenly. There are a lot of strange words, like hysteresis, in the instructions, but once set up it is pretty simple to operate.
Let the oven run for 30 minutes before placing the blade in to temper it.
Hope this helps clear some of the mystery.
Stacy
Some components can be found in thrift stores, other from online suppliers, and most everything can be purchased on Amazon or Ebay. Search for PID, Thermocouple K, SSR, Thermocouple plug connector, 120V cooling fan.
The Oven:
Any manual control toaster oven will do fine. You don't want a digital control oven. One of the old twist-dial types for a few dollars from a thrift store will be perfect. It only needs to be able to set the oven on HIGH or ON. You are going to permanently set it on the highest setting. It needs nothing modified beyond a small hole drilled to allow the thermocouple to stick inside. Some folks wrap a blanket of insulation around the oven to get a little more efficiency. That is a good idea but use the proper insulation. You want a jacket insulation blanket, which controls the loose fibers, like a water heater wrap from the hardware or plumbing shop. Wrap the entire toaster, including the back, and tape the jacket with duct tape. Leave a flap to drop over the front door. This will greatly help the oven regulate temperature and hold a somewhat higher temperature.
The PID:
Most cheap PID controllers are pretty much the same. You want 120VAC input and the ability to take a type K thermocouple.
They often come as a package deal with the PID, SSR, heat sink, Thermocouple, and wires.
Amazon search - PID Temperature Controller Set, PID Temperature Controllers Thermostat Regulator, SSR 40DA Solid State Relay AC 100 to 240V, White Heat Sink and K Type Sensor Thermocouple
The Thermocouple:
The Thermocouple that they often give you with those controllers is pretty useless for most of our purposes, so you will likely need a new one. The temperature range needs to match the desired use. If it is going into an electric toaster oven, it just needs to be a type K that is long enough and rated around 1000F. (BTW, there is a + and - wire, make sure you hook them up right or the display will read wrong.) If your TC has a plug-in probe cord. get a corresponding K-type socket to connect to the PID.
You don't want the ceramic coated TCs for a tempering oven. Just a metal clad probe.
Amazon search - 3M K-Type Thermocouple 100mm Sensor Probe Temperature From -100°C to 1250°C
How it works:
The SSR is actuated by the DC output voltage from the SSR control circuit on the PID.
The SSR can control 48-480VAC circuits. The SSR amperage rating needs to be enough to run the device being controlled, plus a bit. Most folks just use a 40-Amp SSR. You will need a heat sink on the SSR to keep it from burning out (they only will take 3-5 amps otherwise). A small fan, like from a computer, should be used to cool the heat sink.
A 10-foot 120VAC 15-Amp rated 14-gauge extension cord. It will be cut into four pieces - 3-feet with female socket; 5-feet with the male plug; two 1-foot pieces for connector wires. Strip 6" of the outer insulation off the longer pieces and all the outer insulation off the foot long piece. Strip 1/2" off all the ends to expose bare wire.
Other parts - Some connector strips/blocks or wire nuts,18-gauge wire, a power switch, a 15-amp buss fuse and holder, some miscellaneous parts and screws.
To hook all this up:
Enclosure:
Select or make a suitable cabinet for the controller. While you could mount it all on a flat board, open circuitry with 120VAC is a bad idea. A piece of 1/4" plywood with a plastic bread storage container on the back side to cover the wires will work if you don't want anything fancier.
The PID -
Mount the PID on the board/cabinet. Yours may have come with a case or mounting plate of some sort, so mount it as needed.
Connect the thermocouple to the + and - contact screws. Be sure to observe the polarity of the probe! You may need to use a socket that matches the cord type.
Connect two of the 12" long 14-gauge wires to the AC POWER screws. One should be blacks and the other white (from the extension cord). If the PID has a ground terminal, connect a green wire there.
Connect two 12" long 18-gauge wires to the DC SSR Control screws. They are + and - so it is best to use red and black wires.
There may be some additional jumper wires or clips to connect on the PID as the directions will tell you.
On the SSR:
Mount the SSR on the heat sink as described in its instructions (it may recommend using heat sink compound, which is a good idea). Make sure the cabinet or enclosure has sufficient room to aid cooling.
Connect the red/black wires from the PID to the corresponding+/- DC CONTROL contacts on the SSR.
Connect the black AC wire on the female piece of extension cord to one of the LOAD contacts on the SSR. Connect a 12" long 14-gauge black AC wire to the other LOAD contact.
Mount the SSR, heat sink, and the fan so the air blows through the fins and cools the SSR.
The fan connects to the 120VAC buss strips. (see POWER below)
POWER:
Take the 10-foot extension cord and cut it into four pieces as described in the parts list. There will be a common wire (white) and a load wire(black) and a ground wire (green). This will become the power-in and power-out cords and connection wires.
There will be several things connected to these cords, so installing two power buss/multi-connection strips is simplest and safest, but wire nuts will work. AC connection wires will be white and black. Securely fasten the male and female power cord pieces to the cabinet with cable clamps of some fashion.
Install a SPST power switch and a 15 amp fuse. Connect the black wire from the male power cord (the 6-foot-long piece with a plug) to the switch and the switch to the fuse.
Install a black AC wire from the fuse to the load power buss. At this buss the connections are made to:
The 12" black wires from: The load contact on the SSR: The PID: and The fan.
The white wire from the power cord goes to a common buss at which the connections are made to:
The white wire on the Female power cord end (3-foot piece with a socket): The PID: The fan.
The green wires are connected together.
The toaster oven (or controlled device) plugs into the female cord. The male cord will plug into the wall socket.
Insert the thermocouple into the oven chamber. Affix as needed. If the thermocouple is installed just below the rack/grate/shelf, it can be affixed with a twist of bare wire. That way it reads the temperature close to the blade being tempered. Simplest way of installing is drilling a hole in the back or side and sticking the TC through.
You only want the metal probe in the oven, not its wires. Use a longer probe if needed for larger ovens. The tip of the probe is what reads the temperature, so as long as the tip is where the knife will sit on the rack, it will be fine.
The operation of the PID is simple and the instructions give the setup and programming. A good supplier will offer support help. The basic operation is to set the desired temperature (set point or set value) and turn the control program on. The toaster oven is permanently set at its highest setting and will be turned on and off by the controller and the power switch. The controller will allow the power to flow to the oven until the temperature is reached. Then it will cycle on and off to maintain that setting. The PID will auto tune itself to learn how to hold the temperature evenly. There are a lot of strange words, like hysteresis, in the instructions, but once set up it is pretty simple to operate.
Let the oven run for 30 minutes before placing the blade in to temper it.
Hope this helps clear some of the mystery.
Stacy
Last edited:
I archived this thread to my "how to" folder...
. When a ladder diagram, a point to point schematic, and a wire list still doesn't allow them to do it you have to go out and do it yourself.