In general use type water level controller Abstract ：In this design, the water level controller is make up of the host computer, water level sensor, and the conduct device .The host computer use the logic system which make up of the scale digital electron .and photo electricity isolated device, its function has: Water level control, named according to the empty signal of water level gathered to the probe (water lever sensor) , judge and analyze ,then automatically controlled the electrical machinery of water pump and stops; Show water level, which means that whenever water level at the time of every seat that established, then the indicator lamp light in this water level will be turn on. And operator must stop the electrical machineries supplying water pump, When the water level begin dropping down, the water level in indicator lamp will be gradually put up from high to lower, If the indicator lamp does not put up in order then should carry on trouble shooting. In normal cases, dry up indicator lamp of water lever is turned on all the time, light goes out in condition of breaking the water leveling or under the drying up water level, the other indicator lamps are vary with different water level; The Peak water level alarm, which means reach the peak level set up in water level, the alarm begins to report; Dry up water level and breaking water lever Alarm: if some reason make water level lower than the dry up water level or water level sensor which connected to wire blow off, controller automatically alarm, shut off the electrical machinery of water pump, stop supplying water, stop the accident getting more serious, if belong to the trouble of wire breaking, it can resume to normal work after connecting the line; When the water level has already dropped to the drying water level, we need to force water supplying manually after fixing a breakdown, waiting for water level is higher than the drying water level ,can enter the automatic state of a control to rise to and carry on the normal water supply. Give the definitely signal through the water level sensor, and finish the above-mentioned functions, keep the water level within the fixed range. Boiler water level control system in this text probe into EDA technology, it has good logic synthesize and optimize the function, at the same time, his design cycle are short, with high efficiency design and low design risk, the technological module of EDA water level instead of the key circuit of control. This article mainly explain EDA technology and his key circuit module Key word：Water level sensor, photoelectrical coupler, relay, power, and EDA technology
