I wanted a self-switch-off for a PICAXE project so I knocked up this circuit
The pushbutton applies power to the PICAXE. The PICAXE sets the output high to switch the FET on, keeping the AXE powered when the button is released. The trouble is, it doesn't work. Without the PICAXE in circuit, pulling the gate high worked OK but when connected to the PICAXE, the FET is always on.
Guided by research on the forum, I devised this
It works exactly as required.
My question is why doesn't the first circuit work? As must be obvious, I'm an inexpert electronics designer so an over-simple explanation will be welcome.
Thanks,
Derek
PS the P channel FET is overkill but it's all that I have to hand.
The pushbutton applies power to the PICAXE. The PICAXE sets the output high to switch the FET on, keeping the AXE powered when the button is released. The trouble is, it doesn't work. Without the PICAXE in circuit, pulling the gate high worked OK but when connected to the PICAXE, the FET is always on.
Guided by research on the forum, I devised this
It works exactly as required.
My question is why doesn't the first circuit work? As must be obvious, I'm an inexpert electronics designer so an over-simple explanation will be welcome.
Thanks,
Derek
PS the P channel FET is overkill but it's all that I have to hand.