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Discussion Starter #1
Hey guys, I'm currently racking my brain trying to figure out how to get my latest idea to work. I want my radio to stay on when I turn the car off and take my key out until the driver's side door is opened and then closed. If the door is already open when the car is turned off, I want the power to turn off as soon as the driver's door is closed.

I know that if I want to keep the radio on until the door is open, I can use the diagram below, but keeping it on until the door is opened and then closed is something I'm just having trouble with.



Anyone have any ideas?
 
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Does the stereo have to turn off immediately after you close the door?

If you can wait a few seconds after you close the door(s), you can hook your trigger to the light dimmer line. It goes to ground to turn on the light (even if the light is turned off), and slowly goes high. The relay will turn off around 8 volts or so.

The door key light, and ignition light both use the same line as the overhead ones:
http://www.cygnusx1.net/supra/library/TSRM/d/D_23.html

Just an idea that may help. You would need to reconfigure your wiring though.
 
J

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I'm pretty sure that I see a problem with your wiring diagram. It appears as though the radio will come on regardless of the position of the ignition switch whenever the door is closed, and shut off whenever the door is open.

If you use a transistor circuit to control voltage to the relay, you could have better success with your idea.

I'd probably use 3055 NPN transistors, because they're readily available, and cheap.

Your design needs to have some inputs... Ignition curcuit being one of them. When the ignition is on, the circuit should reset, allowing current to pass through to the relay, and the stereo is on.

When the ignition is shut off, the circuit must keep conducting.

Whent he door is open AND the ignition is off, the shut-off circuit must prime, then, when the door is closed, the shut-off must trigger.

In function, it's actually not much different than the headlight safety feature that's incorporated in the car from the factory, except that one just waits for the driver's door to open.

I'll draw up a diagram, and post it when I have time.
 

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Discussion Starter #6
JDMG said:
I'm pretty sure that I see a problem with your wiring diagram. It appears as though the radio will come on regardless of the position of the ignition switch whenever the door is closed, and shut off whenever the door is open.

If you use a transistor circuit to control voltage to the relay, you could have better success with your idea.

I'd probably use 3055 NPN transistors, because they're readily available, and cheap.

Your design needs to have some inputs... Ignition curcuit being one of them. When the ignition is on, the circuit should reset, allowing current to pass through to the relay, and the stereo is on.

When the ignition is shut off, the circuit must keep conducting.

Whent he door is open AND the ignition is off, the shut-off circuit must prime, then, when the door is closed, the shut-off must trigger.

In function, it's actually not much different than the headlight safety feature that's incorporated in the car from the factory, except that one just waits for the driver's door to open.

I'll draw up a diagram, and post it when I have time.
Now that I look at that first diagram and think through it, you're right...it will cause the radio to turn on whenever the door is opened, which is what I don't want.

I found this, and I think it similar to what you're talking about. I just need to figure out how to get it to do what I want. ;)

 
J

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The following circuit should work.



TR1 and TR2 are N3055 NPN transistors (Although you should be able to use any cheap NPN transistor.)
D1 - D4 are N14004 2A diodes (Or any 2A diode, really)
C1 is your buffer capacitor. The size of this capacitor determines the maximum running time after the ignition is switched off. With the current drain through the N3055 transistors a value of 100mF should give you a few minutes.
R1 drains C1 when the door is opened. 100 Ohm will provide a reasonable current limitation and still drain the capacitor by the time the door is closed again.

To obtain the +12VDC when the door is opened, you can use a relay with your +12VDC fused source on pins 30 and 86, with pin 85 attatched to the door switch, and 87 to the circuit.

You can probably replace the transistors with relays if you can get them cheaply, but the transistors are usually much cheaper, and simpler for this kind of application.

(EDIT:)
Whoops! I forgot to indicate the largish resistors that should go at the base terminals for the resistors. These should have 100k resistors or so on them, as the transistor is not just a switch, but potentially an amplifier. This is also needed to extend the life span of the delay circuit with the capacitor!
 

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Discussion Starter #8
JDMG,
Thanks for the help...I'm quite confused by the diagram(not because of the quality, but because of my lack of knowledge about transistors and resistors ;)), but I'll try to work my way through it.

By the way, the first diagram does in fact work. ;) What I think we probably both overlooked is the fact that on the relay on the left, the coil is only energized when both the door is closed and when the radio is already on. Once the radio turns off, if the door is opened and then closed, the left relay will get ground on terminal 85, but will not get +12 volts on terminal 86 because the radio will already be off. ;)
 
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