how to convert volts into amps
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=122266
Printed Date: April 26, 2024 at 1:36 PM
Topic: how to convert volts into amps
Posted By: still_walkin
Subject: how to convert volts into amps
Date Posted: June 12, 2010 at 7:09 AM
im wiring two devices to my car a voice recording module and a standard ipod/mp3 player docking station and one takes a 9v battery and the other takes 4 aaa batteries. this adds up to 9v and 6 total . which would be the correct amperage to put them at. my guess is 5a fuse . thanks guys
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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Replies:
Posted By: awdeclipse
Date Posted: June 12, 2010 at 7:31 AM
The device determines the amp draw, and the fuse is to protect the wiring. Wire gauge determines the fuse size.
You can't just wire in a 9v and 6v device to 12v on the car. Do these devices have cigarette adapters or how do you plan to wire them to the car?
You may be able to get away with wiring them in series since the total voltage is 13v but I am not sure that is even a good idea.
Posted By: still_walkin
Date Posted: June 12, 2010 at 8:48 AM
Ok here's how I was Planning to do it .I got a voice recorder from radio shack and I wanted to amplify it so I got a simple set of mp3 player speakers rated dc 9v. So I was going to wire the speakers into the voice recorder to make it louder. I was going to use 16 guage wire and a inline fuse To the fuse box. No the dont have cig chagers but the speaker set has a 9dc connection and it plugs to a usb so I can plug into the wall or pc. also use a trunk pin so when the trunk opens the recorder would say "trunk open" .now i could use batteries on these items but I rather have it wired to the car so I don't have to replace batteries. Let's say I use batteries would the trunk pin cause a problem being bolted to the car.
https://www.radioshack.com/product/index.jsp?productid=2102855
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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Posted By: DYohn
Date Posted: June 12, 2010 at 10:32 AM
As was mentioned, you cannot safely power a 9 volt device directly from your car's electrical system. You will need a DC to DC power converter that will generate the 9 volts you require. Go to Radio Shack and ask if they sell a car power adapter for your recorder
And there is no way to "convert volts into amps." They are two different things. ------------- Support the12volt.com
Posted By: still_walkin
Date Posted: June 12, 2010 at 2:41 PM
Understood however I wanted to have a trunk pin switch I want to control both of them can I safely do that and use batteries for the device's. The recommended batteries
-------------
1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Posted By: oldspark
Date Posted: June 12, 2010 at 8:51 PM
still_walkin - I suggest you draw a diagram showing your plan.
If you connect your 6V & 9V devices to 12V, you will probably destroy them (you need a voltage converter).
And what is required to make <whatever> announce trunk_open? (Can you trigger it, or you merely power it up?)
Posted By: still_walkin
Date Posted: June 12, 2010 at 9:01 PM
I'm going to power the devices with the batteries it was designed for . I'm just going to use a trunk pin to trigger it to come on/off when the trunk opens. Ill post the diagram later
-------------
1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Posted By: oldspark
Date Posted: June 12, 2010 at 9:27 PM
Use the trunk pin to complete the device's power circuits.
IE - connect each battery -ve to the wire side of the pin and the device "ground" to the vehicle ground.
Assuming all devices are -ve ground there should be no issues.
The alternative is to have the trunk pin energise a relay that closes the power circuit for the devices - ie, SPST or DPST (DPDT).
(Or powers the voltage converters that power the devices, hence they will not need batteries.)
Posted By: t&t tech
Date Posted: June 13, 2010 at 2:32 PM
When i read this topic heading, i thought i'm in for a totally sarcastic, critical read! LOL! Guess i was kinda dissapointed!  ------------- COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF.
PSALMS 37:5
Posted By: oldspark
Date Posted: June 13, 2010 at 8:47 PM
Yeah - I thought I'd make a fortune selling one of those voltage to current converters. (Cheaper than "smart" battery and voltage sensing isolators, dc-dc battery chargers, etc.)
Posted By: anonymous1
Date Posted: June 13, 2010 at 9:32 PM
I thought this thread would be juicier . . . (no pun intended)
There's nothing wrong in asking for a voltage to current converter, or it's applications.
The OP just used the wrong nomenclature as do a lot of folks.
His original requirements was being able to pwr the 2 devices of different voltages from his 12v supply, which is a pretty easy and low tech thing to accomplish.
Sears sells an adapter that gives 5v, 6v, 9, 12, and some other volts, with various connector ends, for around $10.
He could also get a 7805 and that would probably work ok, or an LM7806, use an LM317. Or a zener diode and transistor.
Both of the devices he has uses very low current so this wouldnt be an issue.
DYohn is correct, volts and amps are 2 different things, but if you have an abundance of one, you can create an abundance of another.
. ------------- I know just enough to be dangerous. VERY dangerous.
Posted By: oldspark
Date Posted: June 13, 2010 at 9:54 PM
I've been buying 12-24V chargers for phones etc for $1.60 to $3 (brand new from shops).
They use the MC34063 dc-dc converter chip inbuilt into a quality fused cig-socket.
Snip off the phone connector; modify components for whatever output...
Bargain of you ask me.
Cheaper than the LM series; ~90% efficiency, and cheaper than the smps version of the LM series that sell for $20!
The above is merely FYI after seeing the $20 SMPS-LM equivalent on another site. Even full-priced phone chargers are only ~$15. (The other site being one full of code & hardware hackers.)
For this application - I'd be tempted with a series resistor, though I'd probably add a zenor & fuse for protection.... But if the internal batteries are to be used, it doesn't matter.... (I'd use one switch to power both devices thru a voltage converter...)
Posted By: haemphyst
Date Posted: June 13, 2010 at 10:48 PM
Simple three-pin 78xx voltage regulators is a perfect method to do what you need, AND you will be able to power them both, easily, through the trunk pin.
They are SIMPLE to wire, need no heat-sink up to about .5A, and you'll wonder how you ever got along without them! LOL They are small enough that you can probably even get them IN THE CASES of your projects, then all you have to do is wire the switched 12 volts right to the project box!
Easy peasy. Don't make it any more difficult on yourself than you have to! For less than $10, plus time, you are done. ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: still_walkin
Date Posted: June 13, 2010 at 10:58 PM
Send me a link where I can buy it
-------------
1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Posted By: haemphyst
Date Posted: June 13, 2010 at 11:47 PM
ANY respectable electronics store will stock them. The Shack might have to special order the 9V, but I'm pretty certain the 5V is a stocked item. (SKU 276-1770) (EDIT: The 9V is not listed even as a special order item.)
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: anonymous1
Date Posted: June 15, 2010 at 1:23 AM
haemphyst wrote:
Simple three-pin 78xx voltage regulators is a perfect method to do what you need, AND you will be able to power them both, easily, through the trunk pin.
Now why didnt I think of that? :D
He can run the 12v in the project housing through a 1A fuse, and pwr both ICs at the same time. All the grounds go together, and the + output for each goes to the center pin of the connectors he buys.
He can use a single pole rocker switch at the 12v side to pwr on both ICs. The whole thing will be in a case the size of a tin of Altoids.
.
------------- I know just enough to be dangerous. VERY dangerous.
Posted By: still_walkin
Date Posted: June 15, 2010 at 2:30 AM
I thinkm. The smallest fuse I have in my cars fuse box is 3amp. Ur saying add the regulator after I tap into the fuse
-------------
1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
Posted By: haemphyst
Date Posted: June 15, 2010 at 8:10 AM
You can get your 12V source from anywhere. ADD A FUSE before the regulator(s), and as long as the fuse you add is a smaller current value than the circuit you tap in the fuse block/panel then you're golden. As mentioned, a 1A would very likely be plenty, and would easily pop before the "smallest" 3A in your fuse box.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: still_walkin
Date Posted: June 22, 2010 at 12:10 PM
heres the update i checked my fuse box and the smallest fuse i have is 10a. so if i use a smaller guage wire i can tap into it. or i can go the route with the cig charger . i pefer the first however if i did the cig i would hard wire it to the fuse box anyways . so im assuming the advantage is the chip in the cig charger....
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1993 sdv
Alpine 4x6 6x9 5 1/4 swr-10d4
alpine v60
12.5 VGA flip down
Nettop pc w/10" touch screen
78nova
5-re audio 5x7 ,10" sub &
Xtx-500.5
"Take the faceplate off get the jumperpack"
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