Hi Everyone,
I am designing an automated hydroponics setup, and have designed a simple circuit to control a solenoid based water valve. In order to reduce current consumption, The circuit uses 12V to retract the solenoid, then lowers the voltage to ~2.5V once retracted. This is used to vastly reduce the power consumption, and reduce heat.
I have completed my board layout, and am finding that I am unable to turn off the circuit.
The circuit in question:
The Enable NMOS is used to turn the circuit on and off. The DRIVE NMOS is used to enable the 12V to flow though the solenoid valve when the ENABLE is high. When DRIVE is low, ~2.5V is present on the solenoid valve.
In measuring the circuit, I am able to change the voltage from 12V to 2.5V successfully, but am never able to turn the circuit off, current is always flowing. Toggling the ENABLE NMOS high or low does have an effect on the current consumption, but never stops current flowing entirely. I am completely baffled at this performance.
Stranger still, If I measure the impedance from Ground to the Drain of the Enable NMOS, I measure Mohms of resistance when ENABLE is low (expected), and measure a couple of ohms when ENABLE is high (also expected). Current is always flowing through the Valve however, despite all debugging means showing as normal...
Any help the community can offer would be greatly appreciated!
I am designing an automated hydroponics setup, and have designed a simple circuit to control a solenoid based water valve. In order to reduce current consumption, The circuit uses 12V to retract the solenoid, then lowers the voltage to ~2.5V once retracted. This is used to vastly reduce the power consumption, and reduce heat.
I have completed my board layout, and am finding that I am unable to turn off the circuit.
The circuit in question:
The Enable NMOS is used to turn the circuit on and off. The DRIVE NMOS is used to enable the 12V to flow though the solenoid valve when the ENABLE is high. When DRIVE is low, ~2.5V is present on the solenoid valve.
In measuring the circuit, I am able to change the voltage from 12V to 2.5V successfully, but am never able to turn the circuit off, current is always flowing. Toggling the ENABLE NMOS high or low does have an effect on the current consumption, but never stops current flowing entirely. I am completely baffled at this performance.
Stranger still, If I measure the impedance from Ground to the Drain of the Enable NMOS, I measure Mohms of resistance when ENABLE is low (expected), and measure a couple of ohms when ENABLE is high (also expected). Current is always flowing through the Valve however, despite all debugging means showing as normal...
Any help the community can offer would be greatly appreciated!