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I need a relay that does this....

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  • I need a relay that does this....

    I am looking for a remote turn on sort of switch. What i want is for it to reset itself everytime it loses 12v. Once it gets 12v, i do not want it to turn on until i press a momentary button.

    Basically... Start the car, let the PC get into its normal mode and i press a momentary switch to turn on my amp and accessories. I want the switch to automatically turn itself off when i turn the car off (removing 12v)

    So what is it that i want?
    Take my advice: Do not try to build a system that includes EVERY feature. Start with the basics, build it to a bug free state, and THEN add on.

  • #2
    use a flipflop on the momentary switch. then have the output of the flipflop and the ignition go into an AND gate then have the output go into the relay. of course you will need to condition the voltages to be +5, not 12v, and you need a MOSFET to power the relay, TTL chips will burn out if you hook them up. Also, use a switchbounce circuit on your momentary switch so it doesn't turn on and off a bunch of times when you push it.

    this will keep the rely on until you turn off the ignition or push the momentary button again.
    Progress - VIA EPIA SP8000 | 120 Opus Power Supply & Case | 1GB Ram | 120GB 2.5" Hard Drive | Bluetooth 2.0 | GPRS/3G | Wifi | Road Runner/LSX 2.0 (waiting for a day skin for 3.0) | iGuidance 4.0 | Lilliput 7"

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    • #3
      Couldn't you just hook the relay coil to be powered through the relay itself? After a momentary switch closes the relay, the relay will hold itself closed. When power is lost, the relay will open, resetting itself. You need a relay with a coil voltage of 12V of course, but that's trivial.

      edit: come to think of it, don't latching relays do exactly that?

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      • #4
        Originally posted by mushin
        Couldn't you just hook the relay coil to be powered through the relay itself? After a momentary switch closes the relay, the relay will hold itself closed. When power is lost, the relay will open, resetting itself. You need a relay with a coil voltage of 12V of course, but that's trivial.

        edit: come to think of it, don't latching relays do exactly that?
        like this?

        Code:
                   ignition
                       |
                       +-------------+
                       |             |
                   switch            |
                       |             |
                +------+---      ----+
                |          relay
                |      +---      --+------  load ---- gnd
                |      |           |
                |     gnd          |
                |                  |
                +------------------+
        Progress - VIA EPIA SP8000 | 120 Opus Power Supply & Case | 1GB Ram | 120GB 2.5" Hard Drive | Bluetooth 2.0 | GPRS/3G | Wifi | Road Runner/LSX 2.0 (waiting for a day skin for 3.0) | iGuidance 4.0 | Lilliput 7"

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        • #5
          Yes

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          • #6
            sounds easier than my original idea
            Progress - VIA EPIA SP8000 | 120 Opus Power Supply & Case | 1GB Ram | 120GB 2.5" Hard Drive | Bluetooth 2.0 | GPRS/3G | Wifi | Road Runner/LSX 2.0 (waiting for a day skin for 3.0) | iGuidance 4.0 | Lilliput 7"

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            • #7
              So i need a latching relay???
              Take my advice: Do not try to build a system that includes EVERY feature. Start with the basics, build it to a bug free state, and THEN add on.

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              • #8
                Or just wire up a normal relay like above.

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                • #9
                  I do this all the time..... I use a diode though, so the switch to activate it doesn't see any load..... since I do this sometimes with micro magnet switches, & they handle like no amperage.....

                  without a diode the jumper wire will feed the output with the switch for the instant it takes for the relay to close.... a diode can eliminate this.....
                  MY NEWEST INSTALL:modded infiniti fx with big screen

                  first windows carpc install........my liquid cooled LVDS screen :D

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                  • #10
                    I'm interested in this, but can't quit decipher your ascii drawing up there.
                    CarPC #3: 99% Complete
                    Pentium M 1.7Ghz, 1GB DDR2 RAM
                    DVD/CD-RW installed in dash below monitor
                    OEM LCD relocated for 7" Touchscreen
                    Wi-Fi, GPS, PS2 controllers...
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                    old carPC

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                    • #11
                      Good news but like the above poster... i could really use a simplified diagram
                      Take my advice: Do not try to build a system that includes EVERY feature. Start with the basics, build it to a bug free state, and THEN add on.

                      Comment


                      • #12
                        here...
                        Attached Files
                        MY NEWEST INSTALL:modded infiniti fx with big screen

                        first windows carpc install........my liquid cooled LVDS screen :D

                        Comment


                        • #13
                          the diode will keep the relay energized through the whole ign cycle & go off once power is removed...... if you use a wire instead of a diode for a spit second any load on the output will be powered by the push button switch... if it can handle the load then the diode isn't necissary, but I always use one just to be "correct"
                          MY NEWEST INSTALL:modded infiniti fx with big screen

                          first windows carpc install........my liquid cooled LVDS screen :D

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                          • #14
                            you could also make this fully automatic by using the 5v usb signal to trip a 5v relay, which will control a 12v source fine..... this is what I did....., but ofcourse this will power up right after mb post's..... to have it fully automatic with a delay you can use a timer like periferal I think it's a vt3? variable timer module.... set it to trip from the 5v usb, & then set a delay of 30-40 seconds.... this of course is more complicated.....
                            MY NEWEST INSTALL:modded infiniti fx with big screen

                            first windows carpc install........my liquid cooled LVDS screen :D

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                            • #15
                              I used one of these to accomplish the same thing. I needed a delay on for about 10 seconds or so after starting the car. This kit does that plus a whole lot more.


                              You assemble it yourself. Took an hour or two and has worked flawlessly since.
                              Originally posted by ghettocruzer
                              I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
                              Want to:
                              -Find out about the new iBug iPad install?
                              -Find out about carPC's in just 5 minutes? View the Car PC 101 video

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