AVR Mini Reflow Oven

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phenoptix
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AVR Mini Reflow Oven

Postby phenoptix » Tue Jan 29, 2013 10:04 pm

The Argos Value Range Mini Reflow Oven!

Three caveats stolen verbatim from the original source you should know:

This uses mains electricity, which will kill you if you touch it. So don't.
It makes things hot (solder melting temperatures), which will burn you if you touch them. So don't.
Solder contains lead. Lead is bad for you. Don't use the oven you use for this for food.


Image

Using the methods outlined in this great post from the RepRap wiki I'm attempting to build a reflow oven for SMD soldering of components. Their method gives a way of turning on or off the toaster (or anything on mains power), where it falls down slightly is in that the newest version of the AVR Mini Oven the temperature sensor switches off at just under 220 degrees C, which we really really need to reach!

However, on opening the oven and probing it's inner workings I came upon a solution! Remove the thermal switch and replace it with the thermally controlled relay! It would mean that the oven was only safe when the Arduino was running though - maybe safe isn't the right word. Without the analogue thermal control it would essentially be a two bar electric heater in a box.

Image

The sensor is on the right, fortunately it is attached with spade connectors, which are also on the relay! Whip that out, put in the relay.

xanthic
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Re: AVR Mini Reflow Oven

Postby xanthic » Tue Jan 29, 2013 10:20 pm

You should be able to tweak that temperature profile array in the code of you don't get the results you want. Looks a damn sight safer than a modded toaster too!

phenoptix
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Re: AVR Mini Reflow Oven

Postby phenoptix » Wed Jan 30, 2013 12:41 pm

After some time spent with breadboard and Arduino the code was up and running and the output shown on screen. Turning on and off the LED on the Arduino is the same as opening and closing the relay.

Image

Next to put the relay in the microwave and turn it on. I don't mind saying that I'm always a little nervous turning something back on when I've just had it apart!

I've drilled some extra holes in the back plate and attached with some screws from an old printer

https://lh5.googleusercontent.com/-oBt3kCJrUFk/UQj6HncUPEI/AAAAAAAAApQ/419M1HmpyWM/s846/2013-01-30+09.45.11.jpg

All stable and happy but could do with a connector so the Arduino shield can be taken away from the oven to work on it!

Here we are put back together with it switched on at the wall!

Image

5 minutes later we have the first board out of the oven!

Image

xanthic
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Re: AVR Mini Reflow Oven

Postby xanthic » Wed Jan 30, 2013 1:15 pm

I'm impressed :) Did you use the kapton template to coat the pads?

Almurray42
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Re: AVR Mini Reflow Oven

Postby Almurray42 » Wed Jan 30, 2013 3:38 pm

Nice! Seems like a brilliantly simple and convenient oven! Could save you a lot of time! Great outcome on the chip!
Image
[MOD IT] [OR BIN IT]

vimes79
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Re: AVR Mini Reflow Oven

Postby vimes79 » Wed Jan 30, 2013 7:00 pm

Looks like its going to be a winner. Proper nice job!!!
Next up a board with a handful of picked and placed components of different type.

If that works then I may take a trip to Argos and an order to Farnell and build my own! Although I am now pretty skint for the month so I may go for the Ghetto Tesco Value 2 Slice toaster edition (£5.99 for toaster and whatever the thermocouple costs or an IR Thermometer gun) just need to remember to take the spring loaded release mech out of the slice slots or you will be dodging 220 degree molten solder as well as a PCB and componants....

In all honesty I wouldn't use this enough to justify hacking one into a reflow oven. I will be sticking with my Hot Air Station and super fine copper SMD tips for my iron. Also my new love for Kapton tape and film which I used for the first time yesterday to shield, hold and block heat and solder while soldering an SMD board.

It looks perfect for Ben and people like him who are planning on making their own designed boards etc... A big saving over a dedicated reflow oven.
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vimes79
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Re: AVR Mini Reflow Oven

Postby vimes79 » Wed Jan 30, 2013 7:00 pm

Looks like its going to be a winner. Proper nice job!!!
Next up a board with a handful of picked and placed components of different type.

If that works then I may take a trip to Argos and an order to Farnell and build my own! Although I am now pretty skint for the month so I may go for the Ghetto Tesco Value 2 Slice toaster edition (£5.99 for toaster and whatever the thermocouple costs or an IR Thermometer gun) just need to remember to take the spring loaded release mech out of the slice slots or you will be dodging 220 degree molten solder as well as a PCB and components....

In all honesty I wouldn't use this enough to justify hacking one into a reflow oven. I will be sticking with my Hot Air Station and super fine copper SMD tips for my iron. Also my new love for Kapton tape and film which I used for the first time yesterday to shield, hold and block heat and solder while soldering an SMD board.

It looks perfect for Ben and people like him who are planning on making their own designed boards etc... A big saving over a dedicated reflow oven.
Supporter of Official Arduinos - BeagleBone - RasPi + EVE
-PROUD OWNER OF RepRap PRO MENDEL 3D PRINTER-
Current Projects : + Twitter Bug RGB + RoboBrrd UK #004 (Wireless IoT Brrd) + "Imp Print" +


Twitter Feed : Raw_Gaming

phenoptix
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Re: AVR Mini Reflow Oven

Postby phenoptix » Mon Feb 25, 2013 2:49 pm

Sorry for lack of updates to this thread! Those of you on twitter will have seen some progress on this. It now has an LCD screen attached to monitor the Time, Target Temp and Actual Temp.

Image

Code to add the LCD to the arduino is

CodeColon Select all

/*

  Toaster Oven SMT soldering control
 
  Adrian Bowyer
 
  2 November 2011
 
  Licence: GPL
 
  LCD Display added by
  Ben Gray
  31 January 2013
*/

// include the library code
#include <LiquidCrystal.h> // LCD Code
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); // LCD Code

const int heatPin =  13;     // the number of the LED pin.  This also controls the heater
int heatState = LOW;         // heatState used to set the LED and heater
long previousMillis = 0;     // will store last time LED/heater was updated
const long interval = 1000;  // interval at which to sample temperature (milliseconds)
const int tempPin = 0;       // Analogue pin for temperature reading
long time = 0;               // Time since start in seconds
bool done=false;             // Flag to indicate that the process has finished

// The temperature/time profile as {secs, temp}
// This profile is linearly interpolated to get the required temperature at any time.
// PLEN is the number of entries
#define PLEN 6
long profile[PLEN][2] = { {0, 15}, {120, 150}, {220, 183}, {280, 215}, {320, 183}, {350, 0} };

// Linearly interpolate the profile for the current time in secs, t

int target(long t)
{
  if(t <= profile[0][0])
   return profile[0][1];
  if(t >= profile[PLEN-1][0])
  {
   done = true; // We are off the end of the time curve
   return profile[PLEN-1][1];
  }
  for(int i = 1; i < PLEN-1; i++)
  {
     if(t <= profile[i][0])
       return (int)(profile[i-1][1] + ((t - profile[i-1][0])*(profile[i][1] - profile[i-1][1]))/
         (profile[i][0] - profile[i-1][0]));
  }
  return 0;
}

// Measure the actual temperature from the thermocouple

int temperature()
{
 return ( 5.0 * analogRead(tempPin) * 100.0) / 1024.0;
}

// Get the show on the road

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2); // LCD Code
  pinMode(heatPin, OUTPUT);
  pinMode(tempPin, INPUT); 
  Serial.begin(9600);
  Serial.println("\n\n\nTime, target, temp");
  done = false;
}

// Go round and round

void loop()
{
  int t;
  unsigned long currentMillis = millis();
 
  if(currentMillis - previousMillis > interval)
  {
    previousMillis = currentMillis; // set next time
   
    // Get the actual temperature
   
    t = temperature();
   
    // One second has passed
   
    time++;   
   
    // Find the target temperature
   
    int tg = target(time);
   
    // Simple bang-bang temperature control
   
    if (t < tg)
    {
      heatState = HIGH;
    } else
    {
      heatState = LOW;
    }

    // Turn the heater on or off (and the LED)
    digitalWrite(heatPin, heatState);
   
    // Keep the user amused
    if(done)
    {
      Serial.print((char)0x07);  // Bell to wake the user up...
      Serial.print((char)0x07);
      Serial.print("FINISHED ");
    }
    Serial.print(time);
    Serial.print(", ");
    Serial.print(tg);
    Serial.print(", ");
    Serial.println(t);
   
    lcd.clear(); //LCD Code
    lcd.print("Time Target Temp"); //LCD Code
    lcd.setCursor(0,1);
    lcd.print(time); //LCD Code
    lcd.print("s"); //LCD Code
    lcd.setCursor(5,1);
    lcd.print(tg); //LCD Code
    lcd.print((char)223); //LCD Code
    lcd.setCursor(12,1);
    lcd.print(t); //LCD Code
    lcd.print((char)223); //LCD Code
   
  }
}

vimes79
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Re: AVR Mini Reflow Oven

Postby vimes79 » Tue Feb 26, 2013 8:09 pm

Ooo the original was done by Dr Adrian Bowyer, the co-founder of the RepRap project and Owner of RepRapPro where I visited to get my printer and the man who actually invented it, refined it to its current version and also invented the Tri Colour/Material add on kit!!! I believe he is currently working on conductive plastics/materials that can be put through the RRP Mendel!! That will be cool if he cracks that! So far I think they are only having sensible results by using large'ish amounts of Silver making it REALLY expensive! But he is the expert when it comes to thermal dynamics and all things temp based!

Nice work Ben! Thats an awesome little reflow oven you hacked, thats a great example of turning something as mundane as a toaster/toaster oven into a seriously handy tool that will likely get used a fair bit! Cant wait to see some more adventurous boards going in!

You should buy a few of those practice boards from Dangerous Prototypes/Seeed that have loads of different pad setups and once you have filled a board just run a hotair rework station (like the one I have - £50 from eBay) hot air blower over and remove the parts, go round again with the hot air (or an iron) and use copper de-solder braid to clean it all up to use again!
Supporter of Official Arduinos - BeagleBone - RasPi + EVE
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