Soft latch on off switch

298

05:24:11

Dave Jones' soft latch power switch. Source: episode #262 of EEVblog on YouTube. Starts to work correctly after approximately 5 second of emulated time. Performs terribly with close to zero loads.

published 10 years ago

faceblast

10 years ago

it oscillates at 6Hz if the switch stays closed

Sine_eyed

10 years ago

I noticed that too. It works nicely though if you tap the switch twice like he said, and set the clock back up to 1s/s.

faceblast

10 years ago

how will that work with contact bounce, i wonder

Sine_eyed

10 years ago

Is there a need for that FET though? I swapped it out for a P-channel BJT and the circuit was fine. Operation was just as good and it was still reading that low current draw..

Sine_eyed

10 years ago

@faceblast- ditch the fet and there's no need to worry about contact bounce right? If there is a need to keep it in the circuit tho, I know an easy little debouncer one could use..

lurken__

10 years ago

@Sine_eyed, you will not notice the contact bounce if you set up the RC correctly. :)

lurken__

10 years ago

The switch does nothing while the cap is charging, so if you put it at 0.6 sec or somewhere around, theres no worries about the bounce. And you will not be able to accidently press it longer to immidetly shut it off again!

Sine_eyed

10 years ago

Ok @lurken__, thanks. Good thing calculating an RC time constant is pretty straightforward- I usually get within at least .2S with most of my fingers and only a couple toes! <X^p

distortion

10 years ago

Can anybody explain to me what those length and width in MOSFET properties are?

wyoelk

10 years ago

@distortion, this link explains it quite well, http://ecee.colorado.edu/~bart/book/mosintro.htm

kennetht

10 years ago

Beesdick

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