Stupid question about a relay

[linvillegorge 10+ year member]

I'm running two amps right now off my Kenwood Excelon. Everything works fine, but I ran my amp remote wires to the battery and I'm using a switch to turn them on and off. This can be a major PITA and I just don't want to risk forgetting to turn the switch off and killing my battery. A relay should solve my problem, right? What should I run the remote lead wire to? Splice into the HU's remote? I know I can run to the ignition wire, but I'd really rather not seeing that I've only done a couple of installs and I really don't wanna screw that up.

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[stones 10+ year member]

(cut and paste)

5.11 How many devices can I attach to my remote turn-on lead? [iDB]

=======================================================================

The remote turn-on lead that most head units will not provide very much

current (usually 250-300mA), so there is a limit to the number of

components you can activate with it. Generally, it is safe to hook up

two devices to the lead without having to worry about problems.

However, if you'll be activating more components, then you should

probably use a relay.

5.12   How do I wire a relay in my system? [iDB]
================================================

There are two types of relays that are commonly used in 12-volt
automotive applications:  Single-pole Double Throw (SPDT) relays, which
have 5 pins, and Single Pole, Single Throw (SPST) relays, which have 4
pins.  Depending on the application, you can use either of these; for
remote turn-on leads (see Section 5.11), an SPST relay is fine,
SPDT relays are often used in alarm installations.  Make sure that you
get a 12-volt relay - this specifies the voltage required to make the
relay "switch."

The connections on the two types of relays look like this:

                SPST                       SPDT
        =====================      =====================
                 (87)                       (87)
             +---------+                +---------+
             |   ---   |                |   ---   |
             |         |                |         |
        (86) | |     | | (85)      (86) | | --- | | (87a - center)
             |         |                |         | (85 - right)
             |    |    |                |    |    |
             +---------+                +---------+
                 (30)                       (30)

Pins 85 and 86 connect to the coil which causes the relay to switch.
On both relays, pins 30 and 87 are normally disconnected.  When the
relay is activated (switched) pin 30 and 87 are then in contact.  The
difference with the SPDT relay is that in the "normal" state, pins 30
and 87a are in contact.

To hook up a relay (either kind) for a remote turn on, make the
following connections:

   *Pin 30*
         +12 Volts (Battery +)

   *Pin 87*
         Amplifiers' remote turn-on terminal

   *Pin 86*
         Head unit remote turn-on lead

   *Pin 85*
         Ground

   *Pin 87a*
         No connection (SPDT only)

 

[linvillegorge 10+ year member]

Thanks man!

 

[stones 10+ year member]

No prob //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[DBfan187 5,000+ posts]

your local car audio shop should carry them.

 

[Prowler573 5,000+ posts]

Radio Shack, Wal-Mart, Auto Zone, etc should have them as well as most likely will be cheaper than at a car audio-specific shop. Somehow they become specialty items when in a dedicated mobile audio retailer and get priced around $10 sometimes.

 

[DBfan187 5,000+ posts]

Radio Shack, Wal-Mart, Auto Zone, etc should have them as well as most likely will be cheaper than at a car audio-specific shop. Somehow they become specialty items when in a dedicated mobile audio retailer and get priced around $10 sometimes.

mine cost $2 at my local shop.

 

[stones 10+ year member]

They charge 16.00 bucks for one at Part Source here up north.

Bastages...

If you goto a wrecking yard and look around you can usually pocket over a dozen for free. //content.invisioncic.com/y282845/emoticons/up2something.gif.dd110ecf3ae4b76050d87598f2f8de7c.gif

 

[KaeZoo 10+ year member]

If your remote turn-on is only connected to two amplifiers right now, then don't worry about a relay. You'll actually draw more current from the remote output with a relay (150-200 mA) than just connecting both the amplifiers (typically about 50 mA each).

 

[maylar 10+ year member]

If your remote turn-on is only connected to two amplifiers right now, then don't worry about a relay. You'll actually draw more current from the remote output with a relay (150-200 mA) than just connecting both the amplifiers (typically about 50 mA each).

I absolutely agree. The Bosch relay that everyone uses for this takes 160 ma and is an inductive load (not good for transistor drivers). Many amp remote inputs are really low current, some are only 1 ma. Look at the spec sheets for the amp remote specs and if they add up to less than 160 ma then you're better off without a relay.