IReflow

Reflow Oven Controller

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
  • MyMenu - OLED plus buttons
• 2 LEDs
• Supports external SSR
• 49x49mm form factor
• 4-40 mounting holes spaced 41mm apart

Parts

• Solid State Relay SSR-25DA 25A /250V 3-32VDC for PID Temperature Controller TE
• Welding Blanket - To over the insides

Toaster

• Oster 6-Slice Toaster Oven, Silver tssttvdfl2
  • 1440 Watts, 12 Amps

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

• N/A with MyMenu card

1. GND
2. VCC
3. SW5WAY - Analog

Programming

Card Driver

• IReflow - Arduino Card Driver - on GitHub
• IReflow - Example Code

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
  • From Programming the Atmega328 - AU in Arduino
• Correct Signature = 0x1e 0x95 0x14;
• Keep old copy too.
• In Arduino IDE 1.6.2 the avrdude.conf file is in a different location

• 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

• The path will be shown in the output

Edit avrdude.conf

• Find the string

part parent "m328"
</prew>

* It should look like

[[File:Atmega328-avdude-conf-fuses-orig.PNG]]

* Change to

[[File:Atmega328-avdude-conf-fuses-au-version.PNG]]

=== u8g OLED library ===

[[File: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
<pre>
U8GLIB_SH1106_128X64 u8g(U8G_I2C_OPT_NO_ACK);	// Display which does not send ACK

MAX31855 Thermocouple Amplifier

• Adafruit Thermocouple Amplifier MAX31855 breakout board (MAX6675 upgrade) - v2.0
• Adafruit Thermocouple tutorial
• MAX31855 Arduino library code

Other

• LiPo Battery Care

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

Layout

Calibration

Lead Solder Profile

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

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

• Good video on How-To

Assembly Sheet

IReflow Assembly Sheet