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Reply-To: "Geraldo Sazias"
From: "Geraldo Sazias"
Subject: Re: Electronic On-Off Switch Using Thyristor?
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Mon, 02 Sep 2002 12:31:52 GMT
NNTP-Posting-Date: Mon, 02 Sep 2002 14:31:52 MEST
You misunderstand me. The Play button IS the "power-on" button (there is no
seperate power button) whilst the Stop button is the "power-off" button (in
my case it's controlled by the MCU).
Below is a description of the operation of the circuit I had in mind.
In the power-off state, no power flows should flow through any component (to
minimize power consumption), thefore a flip-flop cannot be used since it
needs power to react to the inputs. When the Play button is pressed, a
current flows for the duration of the keypress which turns on the thryristor
(or some other component) which in turn allows current to flow to all IC's
of the player, thereby turning it on. The MCU controls a seperate transistor
which will turn off al current to the thryristor thereby resetting it.
I could, off course, designed it such that the MCU is always powered but
asleep awaiting a key press of the Play button and subsequently turning on a
transistor which would power all the other IC's and electronics but I would
prefer a solution which draws no current at all in the 'off' state.
The ELM MP3 player has a nice circuit with the function described based on
transistors (http://elm-chan.org/works/mpc/mpc_c1.png) but I'm wondering if
there's an even simpler solution.
"Bevan Weiss" wrote in message
> You could always use a flip flop (J-K configured as a T type, but with Set
> and Reset inputs too, 4000 series has one just like this can't remember
> number however).
> The clock input for the J-K configured as a T-type would be connected to
> power button, such that pushing the power button would cause the power to
> toggle on and off. The Set input would be connected to the play button,
> such that pressing the play button would turn the device on, but not cause
> it to turn off.
> The actual power switching could be performed using a MOSFET or even a BJT
> and a relay, depends on the requirements, you might even be able to get
> with just using the output gate from the flip flop directly if your power
> requirements are that low (< 10mA or so, the rating of the output gate).
> "Geraldo Sazias" wrote in message
> > Hi,
> > I'm buidling a portable MP3 player but I want an electronic on-off
> > controlled by the 'Play' button, just like in most portable CD players.
> > was thinking of using a TRIAC/Thyristor which is ignited by the play
> > (momentary
> > contact) and which turns-on power to all circuitry. The play button is
> > connected to an I/O port on the MCU.
> > Is this a good idea or are there some other more preferable solutions?
> > Thanks for the advice.
> > GS
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