I want to switch on a 12V 1A(peak 1.4A) solenoid valve for 0.1-3 seconds(set using a trimpot) and then switch it off. I'm using 555(operating at 5V, triggered by a IR sensor which operates on 5V only) in monostable mode to generate a 0.1-3s pulse, which is fed directly to gate of mosfet(IRF540- Mosfet Datasheet). It works fine without solenoid valve connected, but on connecting the valve, the mosfet sometimes switch off at right interval and sometimes it will continuously drive the load.
I have attached the schematics and source and gate voltage graph of the Mosfet. The whole circuit is powered by a 12V 3A SMPS, I have a heat sink attached to the 7805 and measured it's temperature which is near ambient.
555 is working in monostable mode
Mosfet is directly driven by the 555 output pin, with a flyback/freewheeling diode (1n4007) attached across the valve.
Voltage at drain
gate(ch 2) and drain(ch 1) voltage, the gate is going to zero but it oscillating with the drain voltage.
How to make mosfet switch off at right time?
I have attached the schematics and source and gate voltage graph of the Mosfet. The whole circuit is powered by a 12V 3A SMPS, I have a heat sink attached to the 7805 and measured it's temperature which is near ambient.
555 is working in monostable mode
Mosfet is directly driven by the 555 output pin, with a flyback/freewheeling diode (1n4007) attached across the valve.
Voltage at drain
gate(ch 2) and drain(ch 1) voltage, the gate is going to zero but it oscillating with the drain voltage.
How to make mosfet switch off at right time?