D-MARK 101! Fun Facts and How To Build Your Own Reflow Oven

by Dr. Klui

Fun fact about D-MARK, 101 is actually the total number of board parts! Now, before we get into our first real-world application, here are some more fun facts about the board name.

It relates to my son's nickname, who was born in Germany, which at the time was still using the Deutsche Mark as its currency.
It means "Very Good" in the Thai language!

Let’s start with an example to get you familiar with D-MARK, and with using its powerful built- in D-MARK Script (DMSi).

How to Run a D-MARK script

Simply save the script below in a text file named "DMS.txt" on a microSD card and push the reset button once. That’s all!

Example 1: Making Your Own Toaster SMD Reflow Oven

You can buy a cheap reflow oven for SMD soldering these days, but I believe you’ll like this option even more. Just one important note: please don’t use it for cooking your food again!

D-MARK Setup:

Input: A popular B=3950, 100 kΩ NTC, used in most 3D printer heaters (we will give you one as a gift!)
Output: MOSFET output channel 1. which drives the SSR relay connecting to a 1200 W oven

What we will do:

heat to 120° C (248° F), soak for 180 s (turn off when >115° C (239° F) as the heat will keep rising a bit even after switching off the heater, turn on again when lower than 115° C).
heat to 150° C (302° F), soak for 60 s (use 145° C / 239° F as a control set point).
heat to 220° C (428° F), soak for 30 s (use 215° C / 419° F as a control set point).
turn off the heater.

DM Script: you can download the script file here.

// Let's config what we are using, use tab as a separator for parameter, not space.

// we will calculate in degree F
NTC.unit	1
// we use 100 kiloohm NTC having B value 3950
NTC.constant_r0	100000
//set the B value to 3950
NTC.constant_b	3950

//set MOSFET output channel 1 to digital output mode
mosfet_1.mode	digital

// Ready to start our smart toaster reflow controller	

//set a label for the first step heating return loop point as "s1"
:s1
//if the NTC temperature is greater than 239 F, jump to routine "s1_soak"
if.ntc.gt	239,s1_soak
//enable the MOSFET output
mosfet_1.on
//as long as the temperature is not reaching our tartget of 240 F, repeat the loop s1
goto	s1

//s1_soak staring point
s1_soak:

//start the timer from 0 s
set.t0	0

//set "s1_soaking" as a starting loop point for checking time and temperature condition.
:s1_soaking
//if the soaking time reaches 180 seconds, jump to do the step 2 (ramp to 294 F).
if.t0.gt	179,s2
//If the NTC temperature reaches 240 F, close the step 1 by jumping to "s1_done"
if.ntc.gt	239,s1_done
//otherwise output will still be on
mosfet_1.on
//loop s1_done as long as the condition is valid
goto	s1_soaking

//the end point of step 1 as the soaking time reaches 180 seconds
:s1_done
//turn off the output
mosfet_1.digital	0
//loop over the step 1 soaking routine 
goto	s1_soaking

//repeat the same procedure for steps 2 and 3 using different temperatures and soak time
:s2
if.ntc.gt	293,s2_soak
mosfet_1.on
goto	s2

s2_soak:
set.t0	0

:s2_soaking

if.t0.gt	59,s3
if.ntc.gt	293,s2_done
mosfet_1.digital	1
goto	s2_soaking

:s2_done
mosfet_1.digital	0
goto	s2_soaking

:s3
if.ntc.gt	419,s3_soak
mosfet_1.digital	1
goto	s3
s3_soak:
set.t0	0

:s3_soaking
if.t0.gt	29,turn_off
if.ntc.gt	419,s3_done
mosfet_1.digital	1
goto	s3_soaking

:s3_done			
mosfet_1.digital	0
goto	s3_soaking

:turn_off
//when all the steps done, turn off the output
mosfet_1.digital	0
goto	turn_off