Stereo Wiring Mod - Stereo Stays On Until Door Is Opened
04-23-2010, 11:58 PM
#1
Drifting
Thread Starter
Stereo Wiring Mod - Stereo Stays On Until Door Is Opened
Here’s my circuit design for an electrical mod that allows the stereo to stay on until one of the doors is opened. Not yet installed in my 90’ S4, so it’s not fully tested.
It’s basically a miniature 12 volt latching relay with a 6 second activation delay. The delay prevents activation during engine cranking in most situations.
Here’s some photos of the prototype circuit board.
The board is small enough to shrink wrap and will be located behind the center console.
There are four hookup wires, three of them connect directly to the aftermarket stereo’s wiring harness, and the remaining wire connects to the door switch (-) negative ground.
On my 90’ S4, the negative (-) door signal is also conveniently located near the stereo head unit. Since my aftermarket keyless entry is already connected there for courtesy lighting function, I actually will hook this door wire to my keyless entry wiring. So fortunately, not much hacking on the car’s wiring with this mod.
Component list
RL1 – DPDT Latching Relay, 12VDC, two coil, 2A contact rating, eBay, about $7 with shipping
Q1 – NPN transistor, general purpose, 2N4401
R1 – Resistor, 52K ohms, 1/4 watt
C1 – Electrolytic Capacitor, 100 uF, 35 volt
D1, D2, D3 – Diode, 1N4005, 1A, 600V
The time delay can be adjusted by selection of the capacitor and resistor values. The resistor’s value is also a function of the relay coil’s current draw and the transistors gain rating.
There's a similar functioning circuit at the12V.com ... but without the delay using three automotive relays
http://www.the12volt.com/relays/page5.asp#drto
It’s basically a miniature 12 volt latching relay with a 6 second activation delay. The delay prevents activation during engine cranking in most situations.
Here’s some photos of the prototype circuit board.
The board is small enough to shrink wrap and will be located behind the center console.
There are four hookup wires, three of them connect directly to the aftermarket stereo’s wiring harness, and the remaining wire connects to the door switch (-) negative ground.
On my 90’ S4, the negative (-) door signal is also conveniently located near the stereo head unit. Since my aftermarket keyless entry is already connected there for courtesy lighting function, I actually will hook this door wire to my keyless entry wiring. So fortunately, not much hacking on the car’s wiring with this mod.
Component list
RL1 – DPDT Latching Relay, 12VDC, two coil, 2A contact rating, eBay, about $7 with shipping
Q1 – NPN transistor, general purpose, 2N4401
R1 – Resistor, 52K ohms, 1/4 watt
C1 – Electrolytic Capacitor, 100 uF, 35 volt
D1, D2, D3 – Diode, 1N4005, 1A, 600V
The time delay can be adjusted by selection of the capacitor and resistor values. The resistor’s value is also a function of the relay coil’s current draw and the transistors gain rating.
There's a similar functioning circuit at the12V.com ... but without the delay using three automotive relays
http://www.the12volt.com/relays/page5.asp#drto
Last edited by borland; 04-24-2010 at 10:33 AM.
04-24-2010, 02:49 AM
#2
Three Wheelin'
Join Date: Mar 2010
Location: Colorado Springs, CO USA
Posts: 1,307
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3 Posts
Cool.
A bit late to mention this since you already built a nice little module, but the power windows remain active until a door is opened, so you might also just be able to run a relay with its coil energized from the supply power of the window motors.
Where, however, is the stereo being hooked up here? Are you running the power to the stereo through a 1A rectifier?
Cheers,
Paul
A bit late to mention this since you already built a nice little module, but the power windows remain active until a door is opened, so you might also just be able to run a relay with its coil energized from the supply power of the window motors.
Where, however, is the stereo being hooked up here? Are you running the power to the stereo through a 1A rectifier?
Cheers,
Paul
04-24-2010, 10:41 AM
#4
Drifting
Thread Starter
Cool.
A bit late to mention this since you already built a nice little module, but the power windows remain active until a door is opened, so you might also just be able to run a relay with its coil energized from the supply power of the window motors.
Where, however, is the stereo being hooked up here? Are you running the power to the stereo through a 1A rectifier?
Cheers,
Paul
A bit late to mention this since you already built a nice little module, but the power windows remain active until a door is opened, so you might also just be able to run a relay with its coil energized from the supply power of the window motors.
Where, however, is the stereo being hooked up here? Are you running the power to the stereo through a 1A rectifier?
Cheers,
Paul
Yes, the low current +12V signal to the Stereo's Assessory Wire (+12V-Ignition) does go through the 1A diode.
04-24-2010, 05:18 PM
#5
Inventor
Rennlist Member
Rennlist Member
If you remove the chime relay (under the radio), the key can be taken out, and the windows still work until you open a door. (Or until the battery dies, if your door switch doesn't work. IE the lights don't turn on when you open the door.
)FYI: fancy window relay is '85-up. Interior light delay off is '86-up.
