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Yet another DIY reflow oven implementation


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After using a hot air station for my smd work for about two years, I think it is time to upgrade my tools to increase my productivity, so I'm looking for adding a reflow oven to my workbench. I searched the web and found many threads about DIY reflow oven, and there are a couple kits looks pretty neat, but somehow all the kits are no longer available for purchase, so I just have to make my own.

 

First is the oven. I brought a cheap one from Amazon. Well, it's cheap, but already better than the one I has in my kitchen. :)

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Then I start working on the controller. Originally I was planning to use Nokia 5110 LCD for the display, but just when I'm going to start the project, I received an email from the store stating that RobG's 2.2" Touch LCD is back in stock! What a prefect timing! So, my controller end up using a MSP430G2553 + RobG's 2.2" touch LCD.

 

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The board under the LCD is just simple contains the socket for the 2553, a 3.3v regulator, and headers for the LCD, relay, and thermocouple sensor breakout board. The power input is via a mini USB port, and there is also a NPN transistor to power the SSR relay using 5V instead of 3.3V, as I think I read from the web that the SSR i brought form ebay is not quite working with 3.3V trigger.

 

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The thermocouple breakout board is using MAX31855, brought from Adafruit. I brought the type K thermocouple from them too.

 

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Time to put everything together. the front panel of the oven control, the temperature selection knob, and the mode selection knob is removed. I keep the bottom timer knob and use it as the main power switch. The SSR is mounted onto a big heatsink, then put on the bottom of the oven. A hole is drilled to route the thermocouple into the oven chamber. A cheap USB charger is also put inside the oven to used as the power supply, but the temperature keep reporting error occasionally when using that charger, so it end up goes to the rubbish bin. No more error when I use my LG phone charger.

 

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I did my first run and so far looks good. The controller right now just sit on top of the oven, and I'll need to comes up with a way to mount it on the front of the oven panel area.

 

 

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I'm just about to start on a reflow oven project myself. Toaster ovens arent that common here in the UK, but I spotted a nice 1kW 9L one recently. (Small and powerful seems a good combination.)

It's still in the planning stage at the moment, but I think I'll go with an optoisolated triac for power control and a MSP430AFE252 (24-bit ADC with programmable gain) to make my own thermocouple input.

These projects seem popular - for a good reason. Maybe we should have a "Reflow Controller of the Month" contest?  :smile:

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.... I'll go with an optoisolated triac for power control and a MSP430AFE252 (24-bit ADC with programmable gain) to make my own thermocouple input.

 

 

24bits for temperature? That's going to be one VERY precise oven, and that little controller is going to be banging the heck out of that TRIAC trying to keep it juuuuust right... lol.  Can a TRIAC wear out?  Heck, pointing an IR remote control at the door will be enough to throw it off!!!  

 

Then again, some might say 'don't use a hammer to kill a mosquito', but have you ever seen what happens to a mosquito when you hit it with a hammer?

 

 

-------

 

 

Nigel Tufnel: The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and...

Marty DiBergi: Oh, I see. And most amps go up to ten?

Nigel Tufnel: Exactly.

Marty DiBergi: Does that mean it's louder? Is it any louder?

Nigel Tufnel: Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where?

Marty DiBergi: I don't know.

Nigel Tufnel: Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do?

Marty DiBergi: Put it up to eleven.

Nigel Tufnel: Eleven. Exactly. One louder.

Marty DiBergi: Why don't you just make ten louder and make ten be the top number and make that a little louder?

Nigel Tufnel: [pause] These go to eleven.

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I wasn't expecting that all of that 24-bit resolution was going to be useful. However, without any pre-amplification 12-bit SAR was useless (7C resolution at best) and 16-bit SD was only just about passable. To be honest it's more the in-built PGA to save using an op-amp and well... just to see if it works. A single MSP430 to do everything but the heavy lifting would be neat.

 

Anyway, I won't clutter up @@StupidPig 's thread with details of my project. I start my own thread when I have something at least underway.

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...To be honest it's more the in-built PGA to save using an op-amp and well... just to see if it works. 

And that's a perfectly reasonable approach - the scaler makes a lot of sense.  You have to run it on something, so it might as well cut down your BOM and assembly time.  Looking forward to seeing it working!

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