Thermistors aren’t rated to 200C.

?

Tony

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Rob via groups.io
Sent: Wednesday, 3 June 2020 12:07 PM
To: [email protected]
Subject: Re: [homebrewpcbs] DIY Toaster Reflow oven

?

Just curious.

What is wrong with using a thermister and a 100K resistor to read the temperature as an analog number and

displaying it on the ARDUINO serial monitor?

That number will be something like 400 to 1,000

and

At the same time

taking the temperature with a real digital thermometer

and once you know what the target temperature equates to on the thermister then you never need the digital thermometer again.

The rest is simply either solid state or relays ...all readily available cheap and documented stuff for the $3.50 ARDUINO UNO.

Thats the spirit of

===>> home brew pcbs <<====???

?

I went down that path using a PIC16F628 6 years ago using BTA24 as my solid state relay. I sort of kicked myself when I learned ARDUINO a long time later.

If I had used an ARDUINO then I coul dhave left the LCD out of the project.

BUT the fruit of this labor IS the BTA24 carrier board because it can easily be attached to any arduino:

?

?

?

Connecting to an existing temperature controller seems fiddly.

Arduino to LCD touchscreen, type K MAX6675 with suitable type K thermocouple wire/probe, 40A SSR on heatsink.

Someone already posted a link to a PID library, no need to write it. Just tune it. But you must have to tune that oven controller, if not, then it isn't really a benefit.

--
Steven Greenfield AE7HD

?

There are a number of DIY reflow projects on YouTube. The simplest being merely placing the PCB on a hotplate and watching it, the next step up using the hotplate at the soak temperature (drying the volatiles and activating the flux), then a hot air reflow gun to melt the solder.

Or using a toaster oven by manually changing temperature, and watching the board.


A lot of people seem to have stopped there.

Going further requires programming, so you'll find more reflow oven projects on sites like forum.arduino.cc and here is a recent thread from 2020:


Note that it pretty quickly goes from PID controller to watching a hotplate.

I don't know how good it is, but I see even Amazon is selling soldering reflow ovens, lowest price $239.

I'm one of probably a number of people who have the intent, got many of the parts, but never finished. Convection toaster oven found at a thrift store, 320x240 touchscreen so it can display the temperature profile, Arduino, thermocouple interface and type K thermocouples, SSR.

I actually have two tabletop convection ovens. One is a standard toaster oven, the other is meant to put like a chicken or a small roast in it. Both convection. The roast oven seems better suited to putting the controls inside. The standard toaster oven, I was going to put a box next to it with the electronics in it.

--
Steven Greenfield AE7HD

?

Just curious.

What is wrong with using a thermister and a 100K resistor to read the temperature as an analog number and

displaying it on the ARDUINO serial monitor?

That number will be something like 400 to 1,000

and

At the same time

taking the temperature with a real digital thermometer

and once you know what the target temperature equates to on the thermister then you never need the digital thermometer again.

The rest is simply either solid state or relays ...all readily available cheap and documented stuff for the $3.50 ARDUINO UNO.

Thats the spirit of

===>> home brew pcbs <<====???

?

I went down that path using a PIC16F628 6 years ago using BTA24 as my solid state relay. I sort of kicked myself when I learned ARDUINO a long time later.

If I had used an ARDUINO then I coul dhave left the LCD out of the project.

BUT the fruit of this labor IS the BTA24 carrier board because it can easily be attached to any arduino:

?

?

Connecting to an existing temperature controller seems fiddly.

Arduino to LCD touchscreen, type K MAX6675 with suitable type K thermocouple wire/probe, 40A SSR on heatsink.

Someone already posted a link to a PID library, no need to write it. Just tune it. But you must have to tune that oven controller, if not, then it isn't really a benefit.

--
Steven Greenfield AE7HD

?

Connecting to an existing temperature controller seems fiddly.

Arduino to LCD touchscreen, type K MAX6675 with suitable type K thermocouple wire/probe, 40A SSR on heatsink.

Someone already posted a link to a PID library, no need to write it. Just tune it. But you must have to tune that oven controller, if not, then it isn't really a benefit.

--
Steven Greenfield AE7HD

On Jun 2, 2020, at 7:56 PM, Steven Greenfield AE7HD via groups.io <alienrelics@...> wrote:

?Connecting to an existing temperature controller seems fiddly.

Arduino to LCD touchscreen, type K MAX6675 with suitable type K thermocouple wire/probe, 40A SSR on heatsink.

Someone already posted a link to a PID library, no need to write it. Just tune it. But you must have to tune that oven controller, if not, then it isn't really a benefit.

--
Steven Greenfield AE7HD

This oven controller is the one I bought on Amazon


The price has gone up a bit but far less expensive than other solutions suggested though admittedly less capable. If this is a popular requirement, could someone take this on as a DIY project? That is, to wire the two (or maybe 3) buttons of the oven controller through opto-isolators to an Arduino for auto setting the set-temperature for a specific time schedule. The two temp set buttons will set the temp up and down (the power-on default is change temp by 0.1 deg increment which is probably too low). The 3rd button selects the setting change increment to 0.1, 1, 10, or 100 degrees per up or down set-temp button increment. A pretty straight forward and easy code algorithm for the Arduino vs writing PID code for direct control.? Good luck!? -mike

?

Hello Steve.

I took your Electronics101 forum link but most if not all of the messages were several years old.

I think it interesting that the discussions about DIY Toaster reflow ovens was on the Electronics101 forum and not on this forum that I thought was for printed circuit board related topics.

One of the later threads (2013 as I recall) suggested rocketscream but the link did not work.? Going to Rocketscream it did look interesting.? They have a Arduino based controller version 2 for $30 but it is out of stock.? It said the user would also have to buy a 40 amp solid state relay and a MAX31856 thermocouple AD and a thermocouple.

It appears that many or most are building the controller in a separate box and then plugging the toaster oven in to that via the SSR.

I have searched quite a bit for DIY toaster oven articles and the ones I found were several years old and see that places like Adafruit, Sparkfun,? and a couple others at one time had a solution but have since discontinued them.? Does that mean there is little or no interest any more?? Are most builders getting the Chinese board houses to preinstall the smt parts?? By the way,? if you do that then you have to also pay the tariff? whereas? the pc board does not incur the tariff charge.

With the current popularity of the Arduino I would have thought there would be a lot of DIY web page articles to use an Arduino or at least the ATMega328P (like the Rocketscream controller). I would like something like that as I have several (28 but who is counting) blank ATMega328P dip IC's.

If I am understanding the theory right all I need is one of the $30 or so Chinese combos of a digital pid and solid state relay and a thermocouple.? What I am not sure about is how or if I can set the warm up temp and then have it go to the reflow temp and then back down or if I have to do that manually or with some type of other controller.

What is the consensus, is it better to build a reflow toaster oven or build a DIY hotplate reflow system?? I know that Johan Holstein briefly talked about doing a hotplate solution on his RadioStuff forum but never finished the project (as near as I could tell) or published it on his web page.

Thank you.

Jim Pruitt

Discussion of electronic design usually takes place on the electronics101 list. I found lots of hits there.

/g/electronics101/search?q=reflow+oven

It seems fairly simple. Get a toaster oven, preferably a convection toaster oven. Wire up a box with an Arduino in it with thermocouple interface, screen, keyboard and/or rotary controller of some kind, and some way to control the AC line. Put an outlet on it, plug the toaster oven into it. Suspend the thermocouple just above the board. Set the temperature control on the convection toaster oven just high enough that it never turns off during normal operation, but acts as a safety.

Everything else is programming. As others have pointed out, you can look up the preheat, hold, melt, hold, cooldown temperatures, times, and rates in the literature some manufacturers of parts make public.

You can get fancy and modify it more, mounting everything in the toaster oven, but then you have heat to contend with.

--
Steven Greenfield AE7HD

?

?

Hello Steve.

I took your Electronics101 forum link but most if not all of the messages were several years old.

I think it interesting that the discussions about DIY Toaster reflow ovens was on the Electronics101 forum and not on this forum that I thought was for printed circuit board related topics.

One of the later threads (2013 as I recall) suggested rocketscream but the link did not work.? Going to Rocketscream it did look interesting.? They have a Arduino based controller version 2 for $30 but it is out of stock.? It said the user would also have to buy a 40 amp solid state relay and a MAX31856 thermocouple AD and a thermocouple.

It appears that many or most are building the controller in a separate box and then plugging the toaster oven in to that via the SSR.

I have searched quite a bit for DIY toaster oven articles and the ones I found were several years old and see that places like Adafruit, Sparkfun,? and a couple others at one time had a solution but have since discontinued them.? Does that mean there is little or no interest any more?? Are most builders getting the Chinese board houses to preinstall the smt parts?? By the way,? if you do that then you have to also pay the tariff? whereas? the pc board does not incur the tariff charge.

With the current popularity of the Arduino I would have thought there would be a lot of DIY web page articles to use an Arduino or at least the ATMega328P (like the Rocketscream controller). I would like something like that as I have several (28 but who is counting) blank ATMega328P dip IC's.

If I am understanding the theory right all I need is one of the $30 or so Chinese combos of a digital pid and solid state relay and a thermocouple.? What I am not sure about is how or if I can set the warm up temp and then have it go to the reflow temp and then back down or if I have to do that manually or with some type of other controller.

What is the consensus, is it better to build a reflow toaster oven or build a DIY hotplate reflow system?? I know that Johan Holstein briefly talked about doing a hotplate solution on his RadioStuff forum but never finished the project (as near as I could tell) or published it on his web page.

Thank you.

Jim Pruitt

Discussion of electronic design usually takes place on the electronics101 list. I found lots of hits there.

/g/electronics101/search?q=reflow+oven

It seems fairly simple. Get a toaster oven, preferably a convection toaster oven. Wire up a box with an Arduino in it with thermocouple interface, screen, keyboard and/or rotary controller of some kind, and some way to control the AC line. Put an outlet on it, plug the toaster oven into it. Suspend the thermocouple just above the board. Set the temperature control on the convection toaster oven just high enough that it never turns off during normal operation, but acts as a safety.

Everything else is programming. As others have pointed out, you can look up the preheat, hold, melt, hold, cooldown temperatures, times, and rates in the literature some manufacturers of parts make public.

You can get fancy and modify it more, mounting everything in the toaster oven, but then you have heat to contend with.

--
Steven Greenfield AE7HD

?

Discussion of electronic design usually takes place on the electronics101 list. I found lots of hits there.

/g/electronics101/search?q=reflow+oven

It seems fairly simple. Get a toaster oven, preferably a convection toaster oven. Wire up a box with an Arduino in it with thermocouple interface, screen, keyboard and/or rotary controller of some kind, and some way to control the AC line. Put an outlet on it, plug the toaster oven into it. Suspend the thermocouple just above the board. Set the temperature control on the convection toaster oven just high enough that it never turns off during normal operation, but acts as a safety.

Everything else is programming. As others have pointed out, you can look up the preheat, hold, melt, hold, cooldown temperatures, times, and rates in the literature some manufacturers of parts make public.

You can get fancy and modify it more, mounting everything in the toaster oven, but then you have heat to contend with.

--
Steven Greenfield AE7HD

If you're cost-conscience or want to keep it simple, buy one of the PID oven controllers available from AMAZON. I bought one that was ~$35 and can hold ~+/-1 deg C.? It has no time/temp function but that may be possible manually or by externally controlling the TEMP SET button(s) with your Arduino, through opto-isolators.

Make sure you
- Buy a temp controller that operates under PID and has an Auto-Tune function. Mine came with an external 40A solid state relay so can control a large oven.
- That your oven can be switched to permanently on, under it's own temp control (set to a temp above the controller's temp-set) which you can use as a safety override.

Good luck,

Mike

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Jean-Paul Louis via groups.io
Sent: Thursday, 28 May 2020 5:17 AM
To: [email protected]
Subject: Re: [homebrewpcbs] DIY Toaster Reflow oven

I also have a comment about the preheat. It is usually dependent on the type
of flux used in the solder paste. But all my experience with it was that the
preheat is needed to ACTIVATE the flux, not just drive out the volatile out of
the paste. And to do that, preheat was more like 130 degrees C.
Usually, the part data sheet include a typical solder profile, but the solder
paste provider might have a better one.
Like you said, peak temperature should be 30 seconds around 215 degrees C.
Cool down is always as fast as you can, but you need to stay below the stress
limit for the component which is around 2 degrees per second.

Just my two cents,
Jean-Paul
N1JPL

On May 27, 2020, at 3:05 PM, Harvey Altstadter <hrconsult@...>

wrote:

After looking at your profile, i cave a comment or two.

Preheat to 100°C is a good idea to drive off the volatiles in the paste. This

will lessen the possibility of boiling flux causing the part to move, will also
reduce the formation of solder balls. Heating to 450°C is much too high. Tin
Lead eutectic solder melts at 183°C, and normal soldering temperature
should be around 215° to 220°C. The profiles on the manufacturer datasheet
are set up for belt furnace soldering. In that process, the board is on a steel
belt that moves at precise speed through several tightly controlled
temperature zones. The belt speed and the zone length determine the dwell
time at each temperature. That said, I would guess that trying to get that
type of profile in a reflow oven would be difficult. I am thinking that the
thermal response would be too slow. Preheat and cool down would probably
be better served outside the oven on a hotplate.

Harvey (the other one) Altstadter

Using the subject of your message post in Google, I found this DIY project:


It appears to be a pretty complete project, includes all of the necessary design files for having the PCB made, the source and binary code for programming the controller, how to modify the toaster oven, etc. ?Seems to be a pretty complete project. ?
The author doesn't specify which oven he used, but did say the oven was a 1300 watt unit. ?I'd suggest that you choose an oven that has a cavity that's appropriately sized for the projects that you intend to use it for. Remember, the larger the oven, the more time it takes to heat the air & objects inside.. ?
Shorter time to heat up means better control of your soldering process.

HTH,
Dave M