T12 circuit Atmega Soldering Station SMD v2

T12 circuit Atmega Soldering Station SMD

The T12 Quick Heating Soldering Station is an advanced soldering tool that offers a myriad of features for enhanced precision and convenience. One of its notable features is the temperature measurement of the tip, which ensures accurate and consistent soldering temperatures. The temperature control can be easily adjusted using the rotary encoder, making it effortless to find the ideal heat for different soldering tasks. A boost mode can be activated by a short press of the rotary encoder switch, providing a quick temperature rise for efficient soldering. Additionally, a setup menu can be accessed by long pressing the rotary encoder switch, allowing users to customize various settings according to their preferences. The station also incorporates handle movement detection using a ball switch, ensuring that the iron remains in an idle state when not in use. It further detects if the iron is unconnected, preventing invalid temperature readings. To conserve power and extend the lifespan of the iron, a time-driven sleep/power off mode is activated when the iron is unused for a certain period of time. The station also measures input voltage, Vcc, and the ATmega’s internal temperature, providing valuable information to users. All the necessary information is displayed on an OLED screen, enabling easy monitoring of the soldering process. A buzzer is integrated into the station for audible alerts and notifications. Moreover, the T12 Quick Heating Soldering Station allows for the calibration and management of different soldering tips, ensuring accurate temperature readings and optimal performance. User settings can be conveniently stored into the EEPROM, allowing for easy retrieval and setup. Overall, this soldering station offers a comprehensive range of features and functionalities, making it an excellent choice for professionals and enthusiasts seeking precision and efficiency in their soldering tasks.

T12 Atmega Soldering Station SMD v2

  • Temperature measurement of the tip
  • Temperature control via rotary encoder
  • Boost mode by short pressing rotary encoder switch
  • Setup menu by long pressing rotary encoder switch
  • Handle movement detection (by checking ball switch)
  • Iron unconnected detection (by idenfying invalid temperature readings)
  • Time driven sleep/power off mode if iron is unused (movement detection)
  • Measurement of input voltage, Vcc and ATmega’s internal temperature
  • Information display on OLED
  • Buzzer
  • Calibrating and managing different soldering tips
  • Storing user settings into the EEPROM
Schematic T12 Circuit Atmega Soldering Station Smd V2
Schematic T12 Circuit Atmega Soldering Station Smd V2

Power Supply Specification Requirements

Choose a power supply with an output voltage between 12V and 24V which can provide an output current according to the table below. The power supply must be well stabilized. The current and power is determined by the resistance (R = 8 Ohm) of the heater.

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Voltage (U)Current (I) = U / RPower (P) = U² / R
12 V1.50 A18 W
13 V1.63 A21 W
14 V1.75 A25 W
15 V1.88 A28 W
16 V2.00 A32 W
17 V2.13 A36 W
18 V2.25 A41 W
19 V2.38 A45 W
20 V2.50 A50 W
21 V2.63 A55 W
22 V2.75 A61 W
23 V2.88 A66 W
24 V3.00 A72 W


T12 Circuit Atmega Soldering Station Smd V2
T12 Circuit Atmega Soldering Station Smd V2

Temperature Measurement and OpAmp Considerations

A thermocouple (temperature sensor) is located in the T12 soldering tip. It creates a minimal voltage depending on the temperature difference between the hot end and the cold junction (about 22 microvolts per degree Celsius). To measure this, the heater must be switched off, since both share the same connections. The low voltage is amplified by the OpAmp and measured by the ADC of the microcontroller. The LMV358 is a very cheap and versatile OpAmp, but not the ideal choice for this task because it has a fairly high input offset voltage and is quite noisy. Although the Soldering Station also works with this OpAmp thanks to the software’s smoothing and calibration algorithms, I highly recommend spending a little more money on a better one. The OPA2330AIDR or OPA2333AIDR for instance, have the same pinout and can also be used with this board. They provide significantly more accurate and stable temperature measurements.

Heater High Side Switch with N-Channel MOSFET and Charge Pump

The microcontroller switches the heater on and off via the MOSFET. Since the temperature measurement must be done over the same line and against
ground, the MOSFET has to be placed between the supply voltage and the heater (high-side switch). A P-Channel MOSFET is normally used for this configuration. However, N-Channel MOSFETs usually have a lower resistance (RDS (on)), in the case of the IRLR7843 only 3 milliohms. A low resistance means a higher efficiency and a lower heat development of the MOSFET. For an N-channel MOSFET to function as a high-side switch, an additional circuit is required to maintain a positive GATE-TO-SOURCE voltage after the MOSFET is switched on. This is done using a so-called charge pump consisting of a capacitor and a diode.

BOM for assembling the T12 soldering station

Resistors SMD
Capacitors SMD
FMMT619Q1Transistor SMD SOT-23-31
IRLR7843TRPBFQ2Mosfet Canal N — TO-252-21
SS54D1Scotty Diode SMA(DO-214AC)1
1N4148WD2Diode — SOD-1231
5V1D3Zener Diode 5v1 — SOD-1231
18VD4Zener Diode 18V SOD-1231
ATMEGA328P-AUU1Microcontroller — TQFP-321
78M05U2Voltage regulator 5V TO-252-21
OLEDOLEDDisplay OLED I2C — 0,96” 128×641
KF350-3.5mmP3,P2,P12 pin connector — KF350-2P3
ICSP-6ICSPAVR ICSP 6 pin connector1
3x6x2.5RESETTouch switch — 3.0×6.01
16MHZX1Crystal — HC-49S1
Rotary EncSW1BOURNS PEC11R-4 F-S X Rotary Encoder or equivalent1


Download files



Source: https://oshwlab.com/wagiminator/z-solderingstation-smd-v2

License: CC-BY-SA 3.0

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Xtronic.org blog author. Electronics technician for the technical school of Brasilia - Brazil. Interested in electronics, circuits and technology in general.

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