changing 12v dc
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=100978
Printed Date: May 02, 2024 at 4:17 AM
Topic: changing 12v dc
Posted By: spaspecker
Subject: changing 12v dc
Date Posted: January 09, 2008 at 4:50 PM
not sure if i'm in the right section so apologies in advance if wrong.
how would I change 12vdc to another voltage? reason for question is a potential project requires the use of an illuminated pushbutton, the illumination is by way of a LED that uses 1.6v dc, but my power supply is 12v dc.
how do I "stepdown" 12v dc to 1.6v dc
thanks in advance
Replies:
Posted By: tedmond
Date Posted: January 09, 2008 at 8:34 PM
use a voltage regulator.
Posted By: i am an idiot
Date Posted: January 09, 2008 at 9:07 PM
A 1K resistor should do the trick. If there is a ground wire on the switch it's sole purpose is to supply ground to the LED. You can insert the 1K (1000 Ohm) resistor in series with the ground wire.
Posted By: KPierson
Date Posted: January 09, 2008 at 9:24 PM
A resistor won't drop the voltage, but it will limit the current which should protect the LED from damage. A voltage regulator would be the best way to actually convert the voltage, but overkill for a simple LED. They make adjustable voltage regulators where you can select the output with a few components. What kind of illuminated push button are you using? ------------- Kevin Pierson
Posted By: spaspecker
Date Posted: January 10, 2008 at 3:42 AM
my idea is to use this button as a start button in my car:
https://cpc.farnell.com/jsp/search/productdetail.jsp?sku=SW02731
i already have a start button wired in, but i want to change it for one that illuminates. it says that the forward voltage for the LED is 1.85v dc, so i know i can't feed it 12v
Posted By: KPierson
Date Posted: January 10, 2008 at 8:09 AM
I would throw a 750 ohm resistor on there and be done with it. As long as you keep the max current below 20mA you shouldn't have to worry about the voltage difference.
-------------
Kevin Pierson
Posted By: spaspecker
Date Posted: January 10, 2008 at 12:28 PM
not sure what's going through it, current button is wired like this:
30: +12v constant
87: starter motor
85: +12v ignition (switched)
86: one side of momentary switch, the other side to ground
but I'll try the resistor suggestion
Posted By: tedmond
Date Posted: January 10, 2008 at 3:16 PM
you got that relay wired up wrong. do you plan to allow start on the push only? or with key as well? if just with push button 85 - 12v @ ignition harness
86 - to push button (ground push button)
87 - high current 12v
30 - to starter wire on car. (motor side)
if you wish to start using key and using push wire it up like so 85 - 12v @ ignition harness 86 - to push button (ground push button) 87 - high current 12v 87a - starter wire (key side) 30 - starter wire on car. (motor side)
Posted By: KPierson
Date Posted: January 10, 2008 at 4:02 PM
His way would work with or without the key. There is no need to isolate the starter wire from the switch - the switch rests in the open position anyway, so there is no need to cut the starter wire. I have my pushbutton start installed just like in his (30 to high current 12vdc, 87 to starter wire) and it works great. ------------- Kevin Pierson
Posted By: tedmond
Date Posted: January 10, 2008 at 10:36 PM
sorry pierson is correct. not enough concentrain ahah. Guess im too worried about my rolled ankle that i got from doin my sports; it hurts gah well thanks for correcting me.
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