Main features are:
- Any thermocouple type irons.
- Additional control mode: On-Off controller (besides PID PWM).
- External power supply: Some standard Notebook power supply DC 19V, 4.74A.
- Small dimensions: It fits into 90mm x 110mm x 45mm (WxDxH) box.
- Easy to assemble.
- Simple design: only a few components (besides Arduino).
The HQ soldering iron HQ20/HQ30 (24V, 48W) was used. It has the E-type thermocouple built in (68uV/degC) but you can change that value in software according to the soldering iron that is used (for example K-type is 41uV/degC).
- Buttons UP and DOWN, changes set-point temperature by 5 degC
- Button SET cycle trough set-point temperature presets: 0 - 150 - 280 -320 -350 degC.
- Buttons UP and DOWN simultaneously, change the operating controller mode ( PID control / OnOff control ).
Here are come measuring results, illustrated in following diagrams.
PID vs ON/OFF, overlapped:
On/Off controller performs well and hold the temperature error inside ±5 ºC, but PID controller performs better (if the overshoot of 15 ºC is neglected) having the steady output temperature error smaller than 1 ºC.
And of course, the Arduino code is given in following file:
for K-type thermocouple:
240°C = 9.84mA
this is correct?
thx for reply
According to diagram on Wikipedia
it should be 41uV/deg, and you have calculated 45.8uV/deg and that should be verified by experiment with external thermometer or some known melting point.
i find for K-type=41,276μV/°C and for E-type=76.373μV/°C
I tested with known melting point cca 183°C with 41uV/°C on program, is approximately to 99.7 correct setting
LM358 can be powered from arduino or external 5V supply ?
if it fails the distortion at the output of operational amplifier
I did not notice and I got a short circuit on OA, arduino received 9V / 19V to A1 and Arduino is destroyed :(
I am trying to remake this project for MSP430.
How you were able to drive IRF640 only with 5 V from arduino? IRF640 needs Vgs = 10 V to fully open.
[quote author="carlazar"]...if the overshoot of 15 ºC is neglected....[/quote]
You can discard the integral term when you are too far away from the setpoint. For slow processes, your integral term will saturate before you get into a controllable region and that will cause an overshoot before the integral term settles (because it needs a negative feed, i.e. overshoot, to get reduced).
The standard solution for this problem it to set Ki to zero when you are not within x% of the setpoint. That point x should coincide with the point where the PWM stops being 100%, but you have not yet reached the setpoint.
@Berto, Thanks for this great advice.
@arunasas, According to IRF640 datasheet, Gate-Source Threshold Voltage is 2.0 - 4.0 V, so it works, somehow.
@lukux, In schematics if the lines are crossing, there is NO junction (┼). To represent junction I use split junction notation (┬┴). Sorry for your loss, but you have joined the lines that are even not the same width in the schematic.
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I have done this soldering station here. Works fantastic. Congratulations, by the way.
However, I am using a hakko 907 genuine. It uses an thermostatic sensor instead of thermocouple.
With some code and hardware changes it is working very well.
Here is the thermistor vs temp relation:
fTemp = -146.9*pow(fVoltage,6) + 2235*pow(fVoltage,5) - 14005*pow(fVoltage,4) + 46255*pow(fVoltage,3) - 84791*pow(fVoltage,2) + 81850*pow(fVoltage,1) - 32536;
Where the sensor wires are just in a volt divisor with a 100 ohm resistance.
I just woould like to know why there isnt any capacitor on 7809 schematic dc regulator.
Hi Bruno, could you pls, send me the changes that was made for hakko 907?
[quote author="thiagogualchi"]Hi Bruno, could you pls, send me the changes that was made for hakko 907?[/quote]
Hello, the main difference is at the sensor type of the soldering iron.
Hakko907 uses a thermostatic instead of thermocouple.
Due to a lack of knowledge (at that time) I used a simple voltage divisor on the sensor.
There are two cons on that: measurements could be better (but is is ok anyhow), and a high current drain due to low resistor series.
My next project is a simple change using an opamp LM358 to get better resolution and low current drain. I will provide it ASAP.
My current project on "SSID06" (corrected) folder:
I realized the LM7809 was heating too much, so I placed a heatsink on it. In order to monitor temp of the heatsink, I placed a LM35 temp sensor sticked on the heatsink. I made a change on the code, so when the 3 buttons are pressed at the same time, I can see the internal temp on the display.
Some other small changes on the code were made. I dont remembar all now, but it is working very well.
Let me know if you need any help.
If I have soldering iron with thermocouple I can change data according to the thermocouple type and it will work? That's really interesting option.
great project. i build 2-3 solder stations and all work almost perfect for many months now. the only issue i had is that sometimes the reading of the temperature on the lcd start to go up & down due to noise i think that lm358 receives.it may take long time for this fault to appear sometimes even days and then dissapears again.any ideas how to resolve that?
Hi, the Dropbox link is broken. Can someone please re-upload it? Thanks!
Here is repaired link https://www.dropbox.com/s/q9zffpwiuw6r4xv/Soldering%20Station%20MOD.rar?dl=0