Vermes
Advanced Member level 4
Presented here time controller is to turn on the pump for approximately 5-7 minutes and turn it off for approximately 15-17 minutes. Those times can be increased or decreased, depending on your needs.
Assumptions of the project:
- analog controller
- ON and OFF times control
- time OFF longer than time ON
- cheap construction
Schematic:
How it works:
Mains voltage fed to the primary winding of the transformer (TS6/63) was decreased to rms value of approximately 12V. Rectifying diodes D1, D2, D3 and D4 make a Graetz bridge, in which full time rectification and supply voltage drop due to the polarization of a p-n junctions of a diode take place. Chip 7809 stabilized the value to a value of 9V. Capacitors C1, C2, C3, C4 filter the voltage. Resistor R1 limits the current of LED1, which informs you whether the controller is on. The main elements of the controller is chip NE555 (timer). It is adapted to nonstable operation. Capacitors C6, C10 are charged by resistors R4, R2, P1, P2, so time OFF in this case will depend on the value of both adjustable resistors. When voltage on the capacitor will reach a value of 2/3 of supply voltage (in this case 6V), the discharging process starts by R2 and P2 and it will last until the voltage on the capacitor reaches 1/3 of the supply voltage (3V), because leg 2 NE555 is shorted with 6 leg.
Current-time graph on leg 3 (output) looks like that:
Elements R5, R6 and Q1 form the negator (in assumptions, the time OFF is the longest time), the output course of which looks like follows:
Value of the reistor R7 sets the value of transistor Q2 base current. R8 limits the current of LED2, which informs you wheter the pump is on. D6 is connected to the relay coil, in order to maintain continuity of the coil current and to prevent the appearance of high voltage.
Pictures:
The PCB was made in thermal transfer method, additionally galvanized. The smallest hole has a diameter of 0,8mm, the largest – 3mm. The front panel was designed in AutoCad R14:
The PCB was designed in Eagle.
Link to original thread (useful attachment) - Czasowy sterownik pompy obiegu wody - projekt.
