truck battery to 12vdc regulated supply

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High4Volts
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truck battery to 12vdc regulated supply

Post by High4Volts » Tue Sep 13, 2005 5:39 pm

I have a NTE956 IC voltage regulator i would like to use to power a 12v DC touch screen. It will be powered by my truck battery. The screen calls for 12vdc @5% regulation. I know during cranking the voltage drops really low so i need it to maintain that 12v. Any suggestions on how to put togather a supply for this useing that IC or is there a simpler way?<p>[ September 13, 2005: Message edited by: High4Volts ]</p>

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Chris Smith
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Re: truck battery to 12vdc regulated supply

Post by Chris Smith » Tue Sep 13, 2005 6:23 pm

If you must be cranky, and use the screen? <p>Are you sure you want to crank the battery, when operating your device? <p>If so, place a small battery in front of the battery,.... diodes attached to the main battery to ensure it doesn’t back flow during cranking, and feed the circuit this way from the small battery to ensure a "time frame and buffer" in such cases. <p>The batteries will equalize on their own, under normal operating conditions.<p>A small 2 amp 12 volt motorcycle battery can hold your circuit steady for minutes or hours depending on your draw. <p>If your draw is really small, try a pack of nicads, NmHy, or even 6 lead acid D cells that can hold a amp or more.
;) ;) :confused:

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jwax
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Re: truck battery to 12vdc regulated supply

Post by jwax » Tue Sep 13, 2005 6:34 pm

If maintaining your screen during that 5 seconds of cranking is all that critical (?) strap a few farads of capacitors on the back of the screen. Use big wire or straps.
What is it you are trying to accomplish?

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jollyrgr
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Re: truck battery to 12vdc regulated supply

Post by jollyrgr » Tue Sep 13, 2005 6:50 pm

How about what the high audio amplifier guys use; a "thunder cap" or "lightning cap". These are ONE HALF to ONE FARAD capacitors at 12VDC. Normally used for high power audio this would work great in your application. The regulator itself should serve as a blocking diode.<p>http://www.dragondistributing.com/soundstormcaps.htm
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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 6:56 pm

--Edited by Positronicle--

High4Volts
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Re: truck battery to 12vdc regulated supply

Post by High4Volts » Tue Sep 13, 2005 7:04 pm

I need to maintain 12vdc whebn the truck is running it's voltage is closer to 13.5 which is to high. I have a 1.3 Ghz computer running a GPS and is tied into my audio system. It gives me 5.1 surround. I have a power supply that supports the computer from the battery and will hold the voltages it needs even while cranking the truck so it does not hardoff and reboot from undervoltage to the PSU. The screen can't tie into the PSU. It dosn't have enough spare wattage on the 12v rail to run it without hurting the PSU. I don't want to buy another PSU just for the screen. So a second battery is not the way i want to go. :)

High4Volts
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Re: truck battery to 12vdc regulated supply

Post by High4Volts » Tue Sep 13, 2005 7:05 pm

dang, forgot the most important thing about the screen. it's 12vdc at 2 amps. The paperwork says it needs to be regulated @ 5%.

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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 7:15 pm

--Edited by Positronicle--

High4Volts
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Re: truck battery to 12vdc regulated supply

Post by High4Volts » Tue Sep 13, 2005 7:18 pm

"I don't see how you have any other choice than to add another power supply(really only a small regulator or so, should do) of some sort."<p>
Can i build one out of a NTE956? :)<p>[ September 13, 2005: Message edited by: High4Volts ]</p>

positronicle
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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 7:23 pm

--Edited by Positronicle--

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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 7:24 pm

--Edited by Positronicle--

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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 7:32 pm

--Edited by Positronicle--

High4Volts
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Re: truck battery to 12vdc regulated supply

Post by High4Volts » Tue Sep 13, 2005 7:45 pm

ah that figures... So what additional parts would i need? positronicle would you happen to have a schematic?

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Re: truck battery to 12vdc regulated supply

Post by positronicle » Tue Sep 13, 2005 7:47 pm

--Edited by Positronicle--

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Chris Smith
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Re: truck battery to 12vdc regulated supply

Post by Chris Smith » Tue Sep 13, 2005 7:54 pm

Just add your second battery in via the diodes and regulate the voltage out. <p>Any two amp regulator will work. <p>The battery can charge to its max on both the first and second battery. <p>The regulator feeds your second device,.... regulated always,.... and the diodes ensure no back flow to lower the voltage during cranking cycles. <p>A 3 to 5 amp small Motor Cycle battery will work the best, because of size and capacitance stored in its liquids.

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