Horn - should it have continuity?

[LL - NY]

Well covered Steve. It's an inductor. And the frequency is in lock step with
the frequency of the horn note. Even an air horn is an inductor if it's
motor compressor driven (such as the Griot's "Italian" horns), although the
ones driven by mechanical compressor (Mack, Kenworth, White, M-B,
ElectroDynamics (locomotive)) are not.  Until Piezo-Electric horns are used
(never gonna happen, unless the hybrid people find horn energy consumption
is a major issue) auto horns will always be inductive loads.

On Mon, Feb 8, 2010 at 1:51 PM, urq <urq at pacbell.net> wrote:

> Most automotive horns are buzzers, with the armature of the buzzer
> connected
> to a diaphragm to amplify the sound.  A buzzer is similar to a relay with a
> N.C. contact in series with the coil winding.  When you apply power to the
> buzzer it pulls the armature of the relay, eventually breaking the circuit,
> which de-energizes the relay.  With the relay de-energized the armature
> returns to rest the switch closes again, which re-energizes the coil.  This
> mechanism is referred to as a relaxation oscillator.
>
> As Brett noted, a horn is a highly inductive load ... a fact accentuated by
> the constant opening and closing of the contacts in the horn.
>
> Steve Buchholz
>
> -----Original Message-----
> From: Mark Rosenkrantz
> Sent: Monday, February 08, 2010 10:04 AM
> Subject: Re: Horn - should it have continuity?
>
> Brett,
> You got me thinking now... is a typical automotive horn an inductive load
> or
> a resistive load?  Not that it particularly matter for this discussion, but
> who's right (I previously said it was a resistive load)?
>
> Because there's no frequency involved, I had surmised that it's purely a
> resistive load on the +12V/-12V side.
>
> What's inside a horn to run the "speaker?"  A DC motor?  I'm not sure...
> but
> I suppose that would make sense.  (I've never had one apart).
>
> It's purely academic, but does an automotive horn's resistance vary based
> on
> it's "state" or "mode?"  I'm no EE, so forgive the terms... by those I mean
> "initial starting," "engaged and running," and "shutting down."  And in the
> "engaged and running" (i.e. on and horn blaring) state, would the load and
> therefore the current vary?
>
> Just curious.  There's probably a wiki out there on just this topic, but
> maybe you, Larry Leung, or someone else might have a ready answer.
>
> Either way, they are fairly high current and since air bags were added to
> the steering column.... in my limited experience... they're all relayed and
> the horn contacts carry only a small current (mA) to energize the relay.
>
> Mark Rosenkrantz
>
> On Mon, Feb 8, 2010 at 12:18 PM, Brett Dikeman
> <brett.dikeman at gmail.com>wrote:
>
> > On Sun, Feb 7, 2010 at 5:53 PM, Radek <radek at istar.ca> wrote:
> >
> > > OK, so to check if the horn is shorted (that's what I'm really after),
> > what should I measure?  It is honking,
> > > BTW and is not on the car.  When I connect it to to a battery, lots of
> > spark is created.
> > > The wire I touch to the battery terminal seems to burn a little hole in
> > the terminal.
> >
> > It's a relatively high-current, inductive load, which is why you get
> > the sparking both on connection and disconnect.  Flyback is what you
> > get when you disconnect an inductive load; it's a big spike of current
> > in the opposite direction.
> >
> > In some cars, the horn is relayed...
> >
> > -B
> >  _______________________________________________
>
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