1: the use of STM8 industrial microcontroller control center. 2: strong and weak electricity through optocoupler isolation, safe operation. 3: the power line and the foot switch line adopts the screw free fast connection terminal, more convenient and reliable. 4: input time, current using high-precision single potentiometer, to reliable input, convenient 5: on-board power supply, state, foot, trigger indicator, working state clearly visible. The control panel of the spot welding machine is a controller which is independently developed for the DIY or the simple resistance welding. The principle of silicon controlled phase shifting triggering is adopted to adjust the time and the current to achieve the purpose of welding. the design of reliable zero crossing detection circuit to that the SCR phase shift accuracy. the controller is compatible with 100A scr. digital control interface, you can display the current time and current settings. time input 1-50, unit cycle (1 cycles is 20ms), current input (30-99%) Types:40A Colour:Red Material: ABS Size: 8 x 6 cm Package Contents: 1 x Main Board 1 x Display Board 1 x Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.