the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
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Car Audio Fiberglass Fabrication I - DVD
Audio Publishers Group
How to Install Your Own Car Stereo System - DVD
Audio Publishers Group
Mobile Security and Remote Start Installation - DVD
Audio Publishers Group
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers
the12volt.com - Free Technical Information for Mobile Electronics Installers
BasicsCar AudioCar SecurityCruise ControlsDiodesDoor LocksOhm's LawPassive CrossoversRelaysResistorsSubwoofer Enclosures Search
the12volt.com - Free Technical Information for Mobile Electronics Installers
the12volt.com - Free Technical Information for Mobile Electronics Installers
the12volt.com - Free Technical Information for Mobile Electronics Installers
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the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
 

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Thiele - Small Parameters
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the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999

Blocking Diodes, Isolating Door Triggers and Sensors, Diodes Across the Coil of Relays

Here's another installer friendly component you should always have handy. Blocking diodes (1N4001/L) are one way valves used in electrical circuits. These are very simple devices that are often real time savers. Other than the amperage rating of the diode, there are only three basic things to remember:

1. Cathode (side with the stripe)
2. Anode (side without the stripe)
3. Anytime the cathode is more positive than the anode, no current will flow.
 
diode
common 4000 series diodes


Isolating Door Triggers:
Some vehicles have two separate (-) door triggers that are isolated from each other, most commonly found on newer GM vehicles. One is for the driver's door and the second is for the rest of the doors. Below is an example of connecting them to one alarm trigger. If you were just to connect to one of these and not both, one or more doors of the vehicle would not be protected by the alarm. When installing an alarm in a vehicle with this type of door trigger (dome lamp) circuit, you must connect to both door triggers for all doors to trigger the alarm. If you were to tie each of these together without the blocking diodes, some features of the vehicle would no longer function properly. Some of the things that could happen are: the door chime / buzzer sounding when any door is opened, rather than just the driver's door, or indicators in the instrument cluster showing false information as to which door is actually opened, and so on.

This diagram would also apply to connecting the (-) outputs of two sensors, such as a glass mic and an impact sensor, to one input of an alarm.

If you have two or more positive triggers to isolate, simply connect the anode side of each diode to each trigger and the cathode sides to the positive input of the alarm.
 
Isolating Negative Door Triggers Isolating Positive Door Triggers


Unless specified, all diodes seen in these diagrams are rated at 1 ampere (1N4001/L).

Diode across the coil of a relay:
The diode provides a path for current when the current path to the relay is interrupted (i.e. switched off). This allows the coil field to collapse without the voltage spike that would otherwise be generated. The diode protects switch or relay contacts and other circuits that may be sensitive to voltage spikes.

Car Audio, Mobile Video, and Fiberglass

Car Audio:
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Ohm's Law
Passive Crossovers & Calculators
Metra Application Guides
Power and Ground Cable Sizes
Subwoofer Enclosures & Calculators
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the12volt's Application Guide
the12volt's Install Bay (forums)
Thiele - Small Parameters
Tools & Equipment

Passive Crossovers:
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Subwoofer Enclosures:
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Sixth & Eighth Order / Bandpass Enclosures
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Thiele - Small Parameters
Fiberglass DVDs

Featured Forum Topics:
 Advanced front speaker systems how-to
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 How to upgrade the Big Three
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Car Audio Hot Topics:
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Mobile Video Forum:
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Fiberglass, Fabrication & Interiors:
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Car Security and Convenience

Car Security:
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the12volt's Application Guide
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Door Locks:
Determining Switch Types
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Special Systems
Add Auto Lock/Unlock

Light Flash / Illuminated Entry:
Illuminated Entry w/Positive Door Triggers
Illuminated Entry w/Negative Door Triggers
Basic Light Flash
Two Wire Light Flash
Adding Light Flash with Siren Output

Car Security & Convenience Forum:
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 Rookies and all seeking advice.
 DEI 528t, siren delay
 Key immobilizers and remote starting
 Tach wire general comments
 What’s the reason to diode isolate?
 How to test for wait to start wire.

Starter Interrupts:
Normally Closed Starter Kill Relay
Normally Open Starter Kill Relay
Passive Starter Kill Diagrams (3)

Fluke 177 Digital Multimeter, 1000V, Backlight, Min/Max/Avg
Fluke 177 Digital Multimeter
• 6000 count display delivers improved resolution
• True-RMS AC voltage and current measurement
• Min/Max/Average recording feature
• Frequency, capacitance and resistance capabilities
• Lifetime Warranty
 



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the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
BasicsCar AudioCar SecurityCruise ControlsDiodesDoor LocksOhm's LawPassive CrossoversRelaysResistorsSubwoofer Enclosures Search
the12volt.com - Free Technical Information for Mobile Electronics Installers
the12volt.com - Free Technical Information for Mobile Electronics Installers
the12volt.com - Free Technical Information for Mobile Electronics Installers
Application GuidesCalculators, Charts, DiagramsDownloadsFind InstallersForumsGlossarySubwoofer WiringToolsVehicle Wiring Active Forum Topics
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
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the12volt.com - Free Technical Information for Mobile Electronics Installers since 1999
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