Do not do this, unless you like seeing your prized possession let out the
magic blue smoke (Often known as the silicon genie). The zener diode is not
fast enough to clamp the edge of a load dump situation


Dennis





> -----Original Message-----
> From: Oliver Broad [SMTP:obroad@TELINCO.CO.UK]
> Sent: Wednesday, 30 August 2000 6:31
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: Best way to get +- Supply from Car battery
>
> If you can tolerate the reduced swing I think you should try to go single
> supply, for Audio it can work very well (for DC applications it is a
> pain).
> Filter your incoming DC with a reasonably high wattage resistor maybe 10
> to
> 100 ohm, then a filter cap. A zener diode could be fitted to protect
> against
> excessive overvoltage. Derive a 1/2 supply reference using a resistor
> voltage divider and a large C to ground. Bias your electronics from this
> so
> the audio swings about this point rather than about ground.
>
> At the recieving end you now have a definite proof that the line is
> connected which could be valuable, two LEDs to indicate OK or an analog SW
> to mute it if open circuit?.
>
>
>
> Oliver.
>
>
>
> >
> > It would be ALOT easier to get +/- 10V regulated wouldn't it?
> >
> > The application is for a stereo (2 channel) Line driver for a car and
> > The specs on the parts (the IC's) call for between +-4 to +-18V I'd like
> > to get as high as possible BUT I don't want to incur unnecessary costs.
> > 10V would be plenty and is found on currently existing devices already.
> > Probably due to the added costs and design complexity that +-12 or
> > greater incurs.
> >
> > a list of IC's if anyone care are Burr Brown OPA2134, DRV134, and
> > INA134. I can provide a link to the data sheets if needed.
> >
> > What I want to do is take an unbalanced RCA output (from a head unit),
> > convert it to a balanced signal (DRV134), run it down a length of cable
> > ,shielded 4 pair twisted (cat 5 cable), and then convert it back to an
> > unbalanced RCA output jack (INA134). the OPA134 (actually a dual chip
> > version OPA2134) will be used in there somewhere for basically a gain
> > setting, probably just before the long cable run. What I envision is a
> > small case w/ inputs:
> > 2 RCA line inputs (50mv-10v depends on source unit)
> > 1 power wire +12 unregulated from the car power system
> > 1 ground wire (chassis automotive Ground)
> > 1 remote turn on wire (from source unit)
> >
> > in this case I'd have:
> > the unit's power supply ( up to +-18V regulated)
> > the DRV134 chip (the Line Driver chip)
> > the OPA2134 OP amp to boost the signal for transit down the wire
> > an output to an 8 position mini-DIN jack
> >
> > down the wire (8 conductor) I'd like to run
> > Common Ground
> > + system power
> > - system power
> > Channel 1 +
> > Channel 1 -
> > Channel 2 +
> > Channel 2 -
> > remote turn on wire
> >
> > at the other end another small case with:
> > a 8 pin mini-DIN connector
> > the INA134 Chip (unbalancer chip)
> > and 2 RCA outputs for connections to external amps
> >
> > right now on parts alone in single quantities my 2 channel line
> > balancer/unbalancer is $14.20 for the IC's and a few needed capacitors,
> > no connectors, jacks, power supply, hence my need to keep the costs
> > down.. I hope to keep the total cost on parts (including case and
> > connectors) to under $25.
> >
> > as far as ripple currents on the voltage regulation go.. I'm at a
> > complete loss.. designing simple fuzz pedals w/ my dad growing up it
> > didn't come into consideration. :).. shouldn't I be paying for this kind
> > of help?? j/k don't ask I can't afford it right now :)
> >
> >                 You guys are great,
> >
> >                         Damon Hopkins
> > --
> > /-=-=-=-=-=-=-=-=-=-=-=-=-\
> > | http://www.openpic.com  |
> > | New OpenSource Pic site |
> > \-=-=-=-=-=-=-=-==-=-==-=-/
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST
> >
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu