Circuit latches solenoids at a distance

J Pelegri and D Ramirez, University of Valencia, Spain -- EDN, 10/14/1999

The circuit in Figure 1 controls low-cost, latching solenoid valves over long distances. For example, it can control one valve 1 km away using two wires and a 12V supply. The circuit provides 700 mA at 12V for the 20 msec necessary for latching a solenoid valve. The CD4538 monostable multivibrator provides an output-pulse width of 100 µsec to 1 sec. The IC consumes 5-nA standby current. The RX₁CX₁ and RX₂CX₂ network determines the output-pulse duration and accuracy. When the voltage on C_A1 reaches 6V, an input trigger occurs, monostable IC_1A delivers an output pulse to Q₁'s gate, and Q₁ sinks the current needed to open the latching solenoid valve. When the voltage on C_A1 drops below 6V, monostable IC_1B turns on Q₂, and Q₂ sinks the current needed to close the latching solenoid valve. C₁ provides power to the solenoid valve. (DI #2426)