Vermes
Advanced Member level 4
Handle:
The handle from Solomon (Pensol) was used in this project. It is also used in Solomon Sl-20 Sl-30 Soldering stations. The heater 50W 24V and thermocouple type K.
Transformer:
In this project, an old transformer with the following parameters: 12V 50VA was used. It can be easily disassembled and re-wound (it consisted of EI core (plate E and I)). The old secondary winding was removed and a new one was wound using a thinner enamelled wire. Also another winding 6V was added using a thin enamelled wire to power the electronics. The transformer after assembling does not hum and heat up.
Driver:
Atmega8 measures the voltage of the thermocouple (previously amplified on operational amplifier). Two channels of ADC converters are used in the processor. One of them is used to measure the voltage of the thermocouple, and the other to measure the voltage of potentiometer for setting the temperature. Using potentiometer is more convenient and practical than to use buttons. The heater can be activated by triac BT139, linked by optotriac MOC 3041 with the optotriac system. It has a zero crossing detection, so you can get rid of distortions resulting from turning off the heater. This also provides galvanic isolation between the electronics and the voltage supplying the heater.
The software was written in Bascom.
The standby mode was added to the device. In the standby mode the station keeps the temperature of 100 degrees Celsius.
Housing:
The housing was made of aluminum and painted black. The front of the housing was made of thin plexiglass, under which printed and laminated panel (designed in Corel) was placed. The back panel is the original one with a cut hole for the socket of the handle.
The board was designed in Eagle and made by thermal transfer method.
The station was calibrated using the thermocouple and meter Unit Ut-33C, it keeps the temperature very well.
Setting the temperature with an accuracy of 10 degrees Celsius from 100 to 450 degrees Celsius. The station keeps the temperature with an accuracy of 3-4 degrees Celsius.
Link to original thread (useful attachment) – Stacja lutownicza na Atmega8 z wyświetlaczem 7 segmentowym