Precision Reflow Oven Controller

Description

I have decided to make my own reflow oven, following in the footsteps of the traditional toaster oven conversion. I know there are many reflow oven controller kits available, but I would like to design one that can be nicely packaged away behind an LCD touch screen. This makes it a bit more expensive, but should hopefully lead to an easy to use and crisp looking piece of lab equipment.

Details

In this project I will take a conventional toaster oven (any kind of toaster oven can be used) and design a precision controller to turn it into a reflow soldering oven. I know there are already plenty of controller kits available out there, but I hope that my project will add a few features other kits don't offer.

The controller will have a Kentec LCD touch display, a precision thermocouple, a solid state relay connected to the heating element of a toaster oven, and a high-speed MSP430 drive it all. The goal is to be able to use the touch screen to precisely edit the reflow Temp vs Time curve or pick from standard curves quickly and easily.

Components

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PCB Prototype Designed
John Boyd • 04/23/2014 at 17:14 • 0 comments

Several hours of tinkering the past few nights has led me to this prototype design. The Kentec LCD I will be using is actually designed to be a booster-pack for the TI Stellaris Launchpad, but I am designing this board to try and verify that I can control the LCD and all of the sensors at the same time. I will probably be ordering this PCB in the near future. If it works as expected, I may design a later board that has the LCD soldered directly on it, but I kind of like how I am able to hide most of the electronics behind the display.
I know not many people have access to Altium designer, which is my preferred design software, but I will post a schematic for anyone to copy into their software of choice.

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Discussions

joaolhullier wrote 01/23/2016 at 17:21

The board is very neat. I'm considering building one myself.
Have you considered using triacs instead of solid state relays to add precision to de controller (you can have different voltage levels instead of just on/off capability) or even power mosfets for cheaper on/off control?

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Adam Fabio wrote 06/22/2014 at 21:08

Hi phreaknik, Thanks for submitting your reflow controller to The Hackaday Prize! I know it will come in handy on my oven - I'm still doing manual reflow. Just as you mentioned, not everyone has access to Altium designer (though there is a free viewer out there) - so Try to put a pdf version of the schematic up.

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Eric Evenchick wrote 04/30/2014 at 05:19

This looks like a much better solution to what I've done in the past... Turn on the oven and hope it sort of hits the reflow profile.

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mikeneiderhauser wrote 04/23/2014 at 19:16

1) It should not take too much room.. Does the 430 have EEPROM? That may be enough. However, since you are using the LCD, you may want some sort of flash to store graphics, profiles, etc..
2) I think 2 would be fine. What chip are you going to use (or are using) to interface to it?
3) Heat should be a concern. These ovens get HOT! I like that idea. Is the terminal and the oven going to be powered from the same AC (to DC converter) source, or are you going to have the oven (through SSR) plug into one outlet and have the controller in another?

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John Boyd wrote 04/23/2014 at 21:15

The MSP430FR5739 that I am using has 16KB non-volatile FRAM memory, but that memory is shared with the firmware. As long as the firmware doesnt take up too much room, I expect there will be plenty of room for saved profiles.

For the thermocouple I am just soldering it to the board and I am going to use a TI ADS1118 external 16-bit ADC to measure the voltage across it. Conveniently the ADS1118 has two differential ADC channels, perfect for two thermocouples!

I was just planning on connecting an LDO voltage regulator to the DC rail in the oven, and then use this regulated voltage line to power the controller.

Thanks for the suggestions! Its good to have someone address these issues before I go order PCBs, haha

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mikeneiderhauser wrote 04/23/2014 at 18:16

Hey.. I have a few questions:
Will you allow for saved profiles?
How many K-type sensors are you going to allow?
Is there any concern that the circuit / touch screen will be influenced or damaged due to the heat of the oven?
Thanks!

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John Boyd wrote 04/23/2014 at 19:11

Great questions!
1) I plan to add functionality for saved profiles, but I might have to add extra storage to the board if the profiles take up much memory.
2) I had only planned on using one (sufficient for my needs), but now that you bring it up, I may add suport for a few more. How many do you think would be good?
3) I also had not considered heat damaging the screen. I plan on making it like a wired terminal, so that you can locate the controller anywhere near the oven that you feel safe. This can vary for different ovens though.

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Precision Reflow Oven Controller

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PCB Prototype Designed

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