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12 volt basic

Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=90702
Printed Date: May 03, 2024 at 12:33 PM


Topic: 12 volt basic

Posted By: mrd05d
Subject: 12 volt basic
Date Posted: February 20, 2007 at 2:34 AM

Now ive read that you shouldnt post in wrong forum but i am confused as to what is the correct forum so...

Im not sure i understand this or not since im new to electrical stuff. Direct current goes one way. I read in the basics that it flows from negative to positive. Does this mean that if i have 4 lamps in series off a battery that the lamps would recieve current from negative terminal to the positive terminal? For instance if i had the following    bat(neg)------(lamp1)-------(lamp2)-------(lamp3)-------bat(pos)     lamp 1 would recieve voltage/current first?  My next question is how do you get a positive or negative polarity in current? Like when i installed my remote starters lock unlock function i had to use a relay to change the polarity. What does that mean? isnt everything positive if its on? I guess im just not catching the basics as well as i should. If someone could help id appreciate it.

My next question involves both relays and car audio so maybe someone could read the question and tell me which to put it in. Or if its possible for one of the admins to move this next question to where they think it should be. My cuzin has a contraption (not sure what it is exactly) that is filtering the bass from the rear speakers and sending it to the subs. He told me his head unit did not have a remote out so what we did was hook a toggle switch to turn on and off the remote wire and ultimately the amp/subs. But since the subs have all the base now because of the filter thing when we turn off the amp/subs we lose all the base. Is there a way to use maybe a relay so when amp/sub is off then the base will return to the rear speakers rather than dissapearing completely?

Thanks in advance and i appologize for not knowing which forum to post in

Rocky 




Replies:

Posted By: KPierson
Date Posted: February 20, 2007 at 10:23 AM

He doesn't have a device that is 'stealing' the bass from the rear speakers and 'giving' that bass to the subs.

He most likely has a high pass filter on the rears, which blocks all the bass below the setpoint.  Depending on how they are installed (assuming they are passive, ie don't require 12vdc to run) they will block different frequencys.  Usually, in the rears, you can go with a lower blocked frequency because the bigger speakers can handle playing lower frequencys (around 150hz is a good generic frequency).

As far as polarity goes, you have your + and you have your -, which is exactly what they say, the + and - of the cars battery.  It is very common in cars to switch the (-) side of devices.  This basically means that you are constantly sending 12vdc to the positive side of the device, but only sending a (-) to it when you want it to be on.  This is convenient for a variety of reasons, and can help keep the total amount of wire need in a car down (since your entire chassis is mechanically electronically attached to the (-) battery terminal).  Different manufacturers do different things, and in some cases your alarm is outputing a (-) signal when the device you are interfacing needs to see 12vdc.  That is when you use a relay to convert.

As far as your lamp question goes, they will all recieve power at the same time.  Try it out!  :)

The time difference would be so small that it wouldn't be detectable.  There are two theories on they way that current travels, the conventional theory states current flows from + to - and the electron flow theory states current flows from - to +.  In college, our basic electronics course went by the conventional theory and the advanced courses when by the electron flow.



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Kevin Pierson




Posted By: Hymer
Date Posted: February 20, 2007 at 12:10 PM
Exactly, both theorys are correct depending on who you talk to.. In the automotive world + is Positive and - is negative or ground. The mettal chassis of the car acts as the conductor rather than a doubleing the wires to complete the circuits. as long as you have a complet circuit +12v -- device -- (-12v ground) things will work. In theory you can use a ground as a switch, but most of the time the device has a metal case that if touched by the cars metal it will complete the circuit causing the device to remain on all the time. Thats why most things are swtched at the +12v side of things. And changing polarity, that is just interfacing to what he device your trying to hook up wants to see.. IE if your lock outputs from and alarm send out +12v and your car needs a (- 12v ground) pulse to activate, then ya have to change polarity with a relay. Useing the +12v outs from your alarm to activate a relay to send a ground pulse whenever you lock and unlock.. Bottom line is , dont get confused by dc theory , just remeber power and ground, and they wont work together unless there is a device or some sort of resistance load between them. Switches are exactly what they say they are, a switch, a relay is what is is, it relays a signal from one point or circuit to another..

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Tire Proz Stillwater Mn
High End Restyling and Comlete Repair




Posted By: mrd05d
Date Posted: February 20, 2007 at 12:28 PM

Thank you for the quick reply i understand most of it if not all. Im still a little blurry on how you would need to convert polarity and how that would keep the ammount of wiring down. Maybe if you could refer me to a good diagram that shows this ill be able to follow a lot better. since my alarm system is simple vats resistance. As far as my cuzins truck it does have a passive high pass filter. so my question is this how can i have it so when toggle is on bass is thru the subs when off it returns to rear speakers?

posted_image





Posted By: mrd05d
Date Posted: February 20, 2007 at 12:33 PM

Btw the little box not labeled is high pass filter. would it be possible for me to put two relays before the high pass filter so if toggle is on then subs work and sound goes through the high pass if toggle is off then sound bypasses high pass and flows directly to rear speakers? is this correct thinking? also i would need two relays correct one for ground wires and one for power wires?





Posted By: Hymer
Date Posted: February 20, 2007 at 12:50 PM
Correct me if Im wrong here audio gurus, but if a guy was to just splice off the rear speaks BEFORE the filter [I know this will mess with impedance a bit, but I have seen it done before.] You will get your bass back to the rears AND be sending the bas to the subs also.. Adding relays into audio works, but can definitly creat a buzz due to the electro magnet in the relay... If it's not a big buck system, I guess it would be worth a try...

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Tire Proz Stillwater Mn
High End Restyling and Comlete Repair





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