getting 11.5V out of a battery ;)

Thread Starter

Garry

Joined Jul 1, 2005
12
Got a small problem... I'm trying to feed an LED display off a car battery (it's a timing display), and need ~11.5V for the LEDs. Using a voltage regulator is more or less not working, as the voltage drop of 1.5-2.5V between input and output is too much for reliable operation (car batteries run around 13.5V when fully charged ... but dropping into 12.xV ranges later on ... (haven't tried at what charge amount, though). I need a total of around 3A peak, but can split it up between the single display elements (10pcs) if necessary ...

Any ideas?

Tnx!
 

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by Garry@Jul 20 2005, 01:26 AM
Got a small problem... I'm trying to feed an LED display off a car battery (it's a timing display), and need ~11.5V for the LEDs. Using a voltage regulator is more or less not working, as the voltage drop of 1.5-2.5V between input and output is too much for reliable operation (car batteries run around 13.5V when fully charged ... but dropping into 12.xV ranges later on ... (haven't tried at what charge amount, though). I need a total of around 3A peak, but can split it up between the single display elements (10pcs) if necessary ...

Any ideas?

Tnx!
[post=9185]Quoted post[/post]​
Low Drop-out regulator

Here is the link to the LD1585 low drop-out adjustable regulator datasheet. It has a maximum voltage drop of 1 volt at 3 amps. You may want to consider this as a solution. The component is available at www.digikey.com.

hgmjr

7-21-05 - Corrected spelling errors...
 

jobarker

Joined Aug 18, 2005
1
Originally posted by Garry@Jul 20 2005, 02:26 AM
Got a small problem... I'm trying to feed an LED display off a car battery (it's a timing display), and need ~11.5V for the LEDs. Using a voltage regulator is more or less not working, as the voltage drop of 1.5-2.5V between input and output is too much for reliable operation (car batteries run around 13.5V when fully charged ... but dropping into 12.xV ranges later on ... (haven't tried at what charge amount, though). I need a total of around 3A peak, but can split it up between the single display elements (10pcs) if necessary ...

Any ideas?

Tnx!
[post=9185]Quoted post[/post]​
LEDs are not sensitive to voltage as long as the diode is forward biased.
Simply use a resistor to limit current to 20 mA or so. The LED should be lit any
time the battery is on
Regards.....Bud
 

mozikluv

Joined Jan 22, 2004
1,437
Originally posted by jobarker@Aug 19 2005, 03:12 PM
LEDs are not sensitive to voltage as long as the diode is forward biased.
Simply use a resistor to limit current to 20 mA or so. The LED should be lit any
time the battery is on
Regards.....Bud
[post=9738]Quoted post[/post]​

ya, that's right provided he's not concerned with the LED brightness. but if he's concerned with that then the regulator would serve his purpose.

moz
 

Thread Starter

Garry

Joined Jul 1, 2005
12
Yup ... Brightness is the issue here ... did some more tests, looks like I do need a bit higher voltage after all ... I will stick to running it off a regulated power supply and just set to whatever V I need after all ...

Tnx @all ...
 
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