Results 1 to 9 of 9

Thread: PSU Wiring Question

  1. #1
    Constant Bitrate
    Join Date
    Jun 2010
    Location
    Vancouver, Washington, United States
    Posts
    221

    Question PSU Wiring Question

    Posting this in the newbie forum because it's more of a concept thing than a technical question.

    So, the always on power line is the big one that has to move the amperage to properly power the devices, correct? For the accessory line, what gauge should that be? Is it more of a voltage sense line that just tells the device (be it a PSU or whatever) that it's OK to power on? I'm just a bit puzzled about this as I don't find much info on the accessory line connections other than they need to be connected for proper functionality.

    Also, this is more audio related, but it is safe to hook up the remote lead on my amplifier to an accessory line, or is this asking for trouble? If not, does a PC output enough voltage on the audio lines for the amplifier to detect that and turn on (it has this function but it cites how headunits put out plenty of power these days).

    -Zack

  2. #2
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    Quote Originally Posted by Ryven View Post
    Posting this in the newbie forum because it's more of a concept thing than a technical question.

    So, the always on power line is the big one that has to move the amperage to properly power the devices, correct? For the accessory line, what gauge should that be? Is it more of a voltage sense line that just tells the device (be it a PSU or whatever) that it's OK to power on? I'm just a bit puzzled about this as I don't find much info on the accessory line connections other than they need to be connected for proper functionality.
    most recommend a 18 ga wire, though you could get away with a 24/22 ga wire. in most devices, it is only a wire that tells the device to turn on--i think most amps say this line draws around 100mA. i remember something about some very old amp designs that used to draw a lot off that wire, but that doesn't apply to 99% of the amps these days...

    Quote Originally Posted by Ryven View Post
    Also, this is more audio related, but it is safe to hook up the remote lead on my amplifier to an accessory line, or is this asking for trouble? If not, does a PC output enough voltage on the audio lines for the amplifier to detect that and turn on (it has this function but it cites how headunits put out plenty of power these days)
    yes, it is fine to connect it that way. i personally don't like the 'audio sense' method because it can be unreliable in some cases, though it can be tough to know if it would or wouldn't work..

  3. #3
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    811
    Hi Zack, soundman98 answered you questions, but here are a few random thoughts anyway.

    I assume you’re talking about the Acc connection on a power amp or PSU, in which case it is a voltage with very little power required; That would be the case in correctly designed equipment, however I too have seen some older designs that require some silly uncalled for requirements.

    Off Track: The “always on” line can be the main power source, however in the case of some OEM car head units this is not always so. Some units use the always on line as a low current source for real time clocks, configuration, station memory and settings. They usually have a separate marked high current line though.

    On a straight amplifier with Acc, +Vin and ground, the Acc is usually a voltage sense with low power requirements that drives a relay or FET.

    In a lot of amplifiers the Acc input also acts as a mute without any turn on/off thump when activated, it’s best to check that on the bench though.

    Newer cars have a reasonable accessory supply line; I’ve used them for many audio installations requiring only a few amperes without problems or noise, in most cases you can pick up a switched line from the back of the existing head unit plug, but everything said, as always, it depends on the system.

    Agree with soundman, the audio sense option in a car can be unreliable. A clean simple option to power the Amp on with a car PC without depending on the Front End, is to switch it from a serial port or USB to serial adaptor and have a tiny program that runs when the OS starts, this sends a signal to power the amp. I think there are a few in the Mp3 shop or by one of the forum guys.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  4. #4
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    ^ i think it is called ampctrl, or something along those lines..

  5. #5
    Constant Bitrate
    Join Date
    Jun 2010
    Location
    Vancouver, Washington, United States
    Posts
    221
    OK, for the Carnetix 2140, I'll tap the ACC line that fed the OEM stereo since this plug is otherwise a waste of $30 (since I ran all new speaker wire).

    For the amplifier, after reading the manual more carefully it does say to connect the ACC line to the remote turn-on lead if the head unit does not meet the requirements. It only asks that a 3A fuse be installed for safety. What's the easiest way to make a delayed turn on for this? It needs a 12V source, so unless I have the PC control a switch that turns on the ACC line for the amp, I may be better off figuring out the boot times and setting up a delay switch to take long enough to let the PC power up first.

    My PC does not have a serial port. I don't believe I can involve the PC in the amp power scenario.
    Last edited by Ryven; 08-24-2011 at 02:51 AM.

  6. #6
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    811
    I’ve seen a few start-up delay control units around here, that’s also what the anti-thump output is for on the PSU. Otherwise a simple RC delay circuit with a FET or small relay to switch +12 once the PSU starts.

    BTW If you want a PC controlled unit then you don’t need a serial port as such, just a USB port.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  7. #7
    Constant Bitrate
    Join Date
    Jun 2010
    Location
    Vancouver, Washington, United States
    Posts
    221
    If I'm using the 12v line on my psu for the monitor could I delay that and split a line to the amp? The additional draw should be minimal... That just might be what I need to do.

    -Zack
    via Droid Charge

  8. #8
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    811
    That should be no problem. Some fluorescent backlit screens can have a startup surge that trips the supply over current, usually on smaller PSU’s with limited 12v current rating. I have a number of control devices including an 8” Led LCD running from the PSU +12 output rail, If you want the option of powering the screen when the PSU is off (for a backup camera) just use a couple of diodes to isolate and steer either supply voltage to the LCD.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  9. #9
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    sorry-- late to the party..

    1. i always recommend connecting the amp to the car power first, so the amp powers up right away. my install works this way, and i have zero issues, but that is not to say every install is problem free. worry about setting up a delay if you have problems like turn on/off pop.

    2. if you have a pop, then there are always different options.

    2a. the ampcntrl program is a great option to guarantee that the amp will not turn on until after the pc boots. the problem is if the carpc never boots, and you try to use a secondary source, then you run into the problem where the amp will be off.. there is a way to use a switch to bypass the pc and power up the amp, but it you can worry aobut that if you choose that route.

    2b. the other option is to use a delay, like the dei 528t. this will turn on the amp after the time you set. the problem is that it might not get rid of the turn on pop if the carpc takes a little longer to boot...

Similar Threads

  1. odd amp wiring kit question
    By yonu in forum Power Supplies
    Replies: 2
    Last Post: 04-29-2010, 09:54 PM
  2. Power Wiring Issue & General Wiring Question
    By speed_krazy in forum Newbie
    Replies: 0
    Last Post: 05-19-2006, 01:17 PM
  3. wiring question
    By the_realscott in forum LCD/Display
    Replies: 0
    Last Post: 10-30-2005, 01:54 AM
  4. PW-60A wiring question
    By l0gic in forum Newbie
    Replies: 11
    Last Post: 10-07-2004, 04:18 PM
  5. LED wiring question....
    By jusatry in forum General Hardware Discussion
    Replies: 3
    Last Post: 03-29-2004, 10:31 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •