From: "Marc H.Popek"
Subject: Re: JK flip flop starts randomly
X-Newsreader: Microsoft Outlook Express 5.50.4133.2400
Date: Thu, 31 Oct 2002 05:06:31 GMT
NNTP-Posting-Date: Thu, 31 Oct 2002 05:06:31 GMT
Organization: AT&T Worldnet
"Ian" wrote in message
> thanks, it worked.
> I cant believe I didn't think of that.
> But then again, I wasn't doing anything like this for over 10 years so...
> "Jeroen" wrote in message
> > "Ian" wrote in message
> > news:firstname.lastname@example.org...
> > > I have a debounced pushbutton switch that clocks a JK flip flop. The
> > purpose
> > > of the device is to turn on and off seat heaters in my car. When the
> > > ignition is on, a relay powers up the circuit, which can then turn
> > > relay that powers the heaters.
> > >
> > > The problem is that when I turn the ignition on, seat heaters could be
> > or
> > > off, but there is no way of telling which one will it be. It appears
> > > random. Both J and K of the Flip Flop are high for toggle mode.
> > >
> > > How can I make JK flip flop always start with, say Q low?
> > Put a simple capacitor/resistor on either R or S input. (or CLR or
> > If active low, then a cap. to ground, resistor to VCC. If active high,
> > resistor to ground, capacitor to VCC.
> > On startup it will generate a short pulse that resets the FF to a known
> > state. Cap=100nF R=10K
> > Jeroen