IReflow

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Reflow Oven Controller

IReflow-MyMenu-P1010248-640px.jpg

Image shows top of iReflow and rear of MyMenu card

Features

  • IR Oven controller
    • Lead free profile
    • Lead profile
  • Type K thermocouple
    • Connection via screw terminal block
  • ATMega328 Microprocessor
    • Arduino compatible
    • 16 MHz
  • FTDI connector for serial USB
  • ISP connector
  • Buzzer to indicate done
  • I2C
  • 2 LEDs
  • Supports external SSR
  • 49x49mm form factor
  • 4-40 mounting holes spaced 41mm apart

Parts

Toaster

Oster-TSSTTVDFL2-1-512px.jpg

Reflow toaster oven conclusions:

  1. This more expensive oven with 4 elements has more than enough power to meet the most demanding temperature slopes and ranges for reflow soldering of both lead-free and leaded solders.
  2. The oven has too much power due to the 4 elements to be run on manual without heating too quickly. The soak zone in the cycle requires a dwell for about 2x-4x the time that the oven would produce under manual control.
  3. The oven high temp thermostat has quite a bit of hysteresis but the high temperature is above the temperatures for both profiles. Set the oven to highest temp and control it.
  4. Probably doesn't need PID control although it would be cooler if it was.
  5. Definitely need PTouch labels on the door for contaminants "Don't cook food in here" and for heat "Gets hot to touch".

Connectors

J1 - 9V DC Power Jack

  • Center = +9VDC (nominal)
  • Shield = GND

J2 - Solid State Relay

  • Driven by transistor to ground
  1. +5V
  2. SSR-Output

J3 - FTDI

  1. GND
  2. GND
  3. +5V
  4. TxD
  5. RxD
  6. Reset

J4 - I2C OLED

  1. +5V
  2. GND
  3. SCL
  4. SDA

J5 - Thermocouple

  1. Thermo + = Yellow
  2. Thermo - = Red

J6 - ISP Download cable

  1. MISO
  2. +5V (+ marked on PWB)
  3. SCK
  4. MOSI
  5. RESET
  6. GND

J7 - Keypad

  1. GND
  2. VCC
  3. SW5WAY - Analog

Programming

Card Driver

Fixing the Device Signature Error in the Arduino IDE

  • The SMT ATMega328P-AU part has a different signature than the UNO.
  • When you try to program the IReflow card using Arduino Uno as the board type you get an error
avrdude: Expected signature for ATmega328P is 1E 95 0F
         Double check chip, or use -F to override this check.
Wrong microcontroller found.  Did you select the right board from the Tools > Board menu?
  • The Arduino IDE needs avrdude.conf changed to program the AU part
  • In earlier versions of the Arduino IDE finding the avrdude.conf file was relatively straightforward
  • Correct Signature = 0x1e 0x95 0x14;
  • Keep old copy too.
  • In Arduino IDE 1.6.2 the avrdude.conf file is in a different location

Ard1p6.PNG

  • Changing it here doesn't work since it's located in a roaming directory at least for Windows 8.1
    • C:\Program Files (x86)\Arduino\dist\default_package.zip\packages\arduino\tools\avrdude\6.0.1-arduino2\etc
  • Other OS versions may be different
  • Locate the avrdude.conf file
    • On my computer it is at: C:\Users\doug_000\AppData\Roaming\Arduino15\packages\arduino\tools\avrdude\6.0.1-arduino2\etc
  • Find it by turning on verbose download in the IDE

Atmega328-menu.PNG

  • The path will be shown in the output

Atmega328-avdude-conf-path.PNG

Edit avrdude.conf

  • Find the string
part parent "m328"
  • It should look like

Atmega328-avdude-conf-fuses-orig.PNG

  • Change to

Atmega328-avdude-conf-fuses-au-version.PNG

u8g OLED library

Ireflow-OLED-640px.jpg

  • Library notes
    • Display characters/variables:
      • Use u8g.print (xx) function, just like the way you did with Serial.print (xx).
    • Change the font:
      • Use u8g.setFont (xx) function to change the font, parentheses "xx" can be replaced by the corresponding font library name (you can search font library in u8g.h within U8glib \utility folder);
      • Large font is recommended for u8g_font_7x13, middle font for u8g_font_fixed_v0r and small font for u8g_font_chikitar;
    • Change coordinates:
      • Use u8g.setPrintPos (x, y) function to change the display of coordinates
  • fonts
  • HelloWorld
    • Uncomment
U8GLIB_SH1106_128X64 u8g(U8G_I2C_OPT_NO_ACK);	// Display which does not send ACK

MAX31855 Thermocouple Amplifier

Other

Algorithm

Piece-wise Linear

#define TIME0_LEADFREE 0
#define TIMET1_LEADFREE 120
#define TIMET2_LEADFREE 165
#define TIMET3_LEADFREE 210
#define TIMET4_LEADFREE 218
#define TIMET5_LEADFREE 600
#define TEMPT0_LEADFREE 22.0
#define TEMPT1_LEADFREE 150.0
#define TEMPT2_LEADFREE 200.0
#define TEMPT3_LEADFREE 252.0
#define TEMPT4_LEADFREE 252.0
#define TEMPT5_LEADFREE -40.0

double getDesiredTempLeadFree(int currTime)
{
  if (currTime < TIMET1_LEADFREE)
    return (TEMPT0_LEADFREE + ((double)currTime                   * ((TEMPT1_LEADFREE-TEMPT0_LEADFREE)/(float)(TIMET1_LEADFREE-TIME0_LEADFREE))));
  else if (currTime < TIMET2_LEADFREE)
    return (TEMPT1_LEADFREE + ((double)(currTime-TIMET1_LEADFREE) * ((TEMPT2_LEADFREE-TEMPT1_LEADFREE)/(float)(TIMET2_LEADFREE-TIMET1_LEADFREE))));
  else if (currTime < TIMET3_LEADFREE)
    return (TEMPT2_LEADFREE + ((double)(currTime-TIMET2_LEADFREE) * ((TEMPT3_LEADFREE-TEMPT2_LEADFREE)/(float)(TIMET3_LEADFREE-TIMET2_LEADFREE))));
  else if (currTime < TIMET4_LEADFREE)
    return (TEMPT3_LEADFREE);
  return (TEMPT5_LEADFREE); // off
}

Mechanicals

OLED

OLED Mechanicals 30654-6.jpg

Layout

IReflow-CAD.PNG

Calibration

Lead Solder Profile

KesterSnPbCurve.PNG

Lead-free Solder Profile

Lead Free

LeadFreeProfile.PNG

LeadFreeProfileParms.PNG

On Bake Setting - Manual Control - Heat/Cool

  • Temp set to 450 deg F
  • Ran oven until thermostat kicked in then shut off

ToasterOvenBakeHeatCoolManual.png

Observations - Leaded Profile vs Manual Oven

Feature Lead Solder Oven (Bake-Manual) Notes
Ramp Up < 1.8 deg C/sec 2.2 deg C/sec max (1)
Soak Temps 150-180 deg C
Soak Time (L) 30-60 secs ~15 secs (2)
Ramp to Peak ~1 deg C/sec 1 deg C/sec
Peak soak 210-224 deg C
Ramp-down Rate
  1. Peak is a bit too fast but average is right on
  2. Soak time needs to be extended 2x-4x the time

Observations - Lead-Free Profile vs Manual Oven

Feature Lead-Free Oven (Bake-Manual) Notes
Ramp Up 1-4 deg C/sec 2.2 deg C/sec max (1)
Soak Temps 150-200 deg C
Soak Time (LF) 60-180 secs < 30 secs (2)
Ramp to Peak 1-4 deg C/sec 1.5 deg C/sec
Peak soak 245-260 deg C 290 max (3)
Ramp-down Rate 1-6 deg C/sec max 1 deg C/sec
  1. Soak time needs to be extended 2x-4x the time
  2. Max temp should be controlled and oven left at highest temp due to hysteresis of the thermostat (pretty wide range)

Table - Bake Setting

Time (secs) Temp (deg C) Slope (degC/sec)
0 25.75
30 44 0.61
60 87 1.43
90 153 2.20
120 206 1.77
150 245 1.30
180 272 0.90
210 290 0.60
240 276 -0.47
270 264 -0.40
300 234 -1.00
330 213 -0.70
360 196 -0.57
390 183 -0.43
420 171 -0.40
450 162 -0.30
480 154 -0.27
510 147 -0.23
540 141 -0.20
570 134 -0.23
600 128 -0.20
630 123 -0.17
660 119 -0.13

Links

Assembly Sheet