|
|||||||
 |
|
|
Thread Tools | Search this Thread | Display Modes |
12-09-2003, 08:25 AM
|
#1 |
|
Admiral
  
Join Date: Mar 2001
Location: Utah
Posts: 5,420
|
Calling all Electrical experts: Have 12 Volts, Need 5 Volts
A mobile radio at work runs off of 12V or 13.8V from a car battery, and one of the devices I'm working on operates on 4-5V DC. Is there something you can get to take those 13V or so from a battery and reduce the voltage?
My boss asked if there was a "DC-DC converter" or something like that, anyone have any electrical knowledge about this?
__________________
And closer... |
|
|
|
12-09-2003, 08:29 AM
|
#2 |
|
Arrrhh!
Join Date: May 2000
Location: LI NY
Posts: 6,807
   |
All you need is a 5V DC-to-DC converter that supplies the proper amperage and should be OK.
__________________
A priest, a paladin and Varimathras walk into a bar... |
|
|
|
|
12-09-2003, 09:05 AM
|
#3 |
|
Admiral
Join Date: Mar 2001
Location: Utah
Posts: 5,420
|
They sell these at Radio Shack? I'll do a quick check in the meantime on their website, I wonder if they're cheap...
At most, it'll draw 170 mA. I'm a struggling Electrical Engineering student, I know!  So should I look for a DC-DC converter with amperage higher than 170 mA?Last edited by skiAtomic : 12-09-2003 at 09:13 AM. |
|
|
|
|
12-09-2003, 09:56 AM
|
#4 |
|
Lieutenant Commander
 
Join Date: Feb 2003
Location: metro detroit, mi
Posts: 930
|
or .... V=IR
V = 12-5 = 7volts I = 170ma = 0.170amps R = V/I = 7/0.170 R = 41.2 ohms put a 42 ohm resistor in there  |
|
|
|
|
12-09-2003, 12:14 PM
|
#5 | |
|
Admiral
Join Date: May 2000
Location: Redlands & San Diego, CA.
Posts: 5,882
 |
Quote:
Not only should be at the hut, but you probably can build one yourself from parts they sell.
__________________
|
|
|
|
|
|
12-09-2003, 12:15 PM
|
#6 | |
|
Fleet Admiral
Join Date: Jan 2000
Location: 742 Evergreen Terrace, Springfield USA
Posts: 9,276
|
Quote:
Nice try, but its not that simple. A cars voltage can range anywhere from 9V when cranking to 15+ volts when running. Just a resistor can't handle this, which is why DC-DC converters exist. |
|
|
|
|
|
12-09-2003, 01:30 PM
|
#7 |
|
Lieutenant Commander
Join Date: Feb 2003
Location: metro detroit, mi
Posts: 930
|
ok, then take 12 and change to 15 then carry out the equation... what device do you have?
|
|
|
|
|
12-09-2003, 01:38 PM
|
#8 | ||
|
Admiral
Join Date: Mar 2001
Location: Utah
Posts: 5,420
|
Quote:
A serial Bluetooth adapter... darn thing needs 5V EXTERNAL power to run  But then again, most of us are spoiled by our external devices being powered by USB lately (my scanner doesn't even have an AC adapter)  Someone over at [H]ardOCP told me this: Quote:
|
||
|
|
|
|
12-09-2003, 06:53 PM
|
#9 | |
|
Plebe
Join Date: Dec 2003
Posts: 3
|
Quote:
A linear regulator (7805 series) is what you need. A resistor alone will not work (as the current flow changes so will the voltage seen by your device). You can use a zener/resistor combination, but why waste time with that when a 7805 will do everything you need. Most 7805s will easily handle 1/4Amp without a heatsink and easily 3/4 to 1 Amp when properly sunk.
__________________
John http://embedded.mistekllc.com |
|
|
|
|
|
12-09-2003, 06:54 PM
|
#10 | |
|
aka the keg killer
Join Date: Dec 2002
Location: Ala-effin'-bama!
Posts: 2,738
|
Re: Calling all Electrical experts: Have 12 Volts, Need 5 Volts
Quote:
http://www.radioshack.com/product.as...Fid=273%2D1811
__________________
"The price of progress is trouble." (C. F. "Boss" Kettering) "50% of the American public has below-average intelligence. 70% of the American public now has regular access to the Internet. Do the math." (unknown) |
|
|
|
|
|
12-09-2003, 07:05 PM
|
#11 |
|
Plebe
Join Date: Dec 2003
Posts: 3
|
Looking at the same site, here's the price for the 7805 regulator
http://www.radioshack.com/product.as...%5Fid=276-1770 |
|
|
|
|
| Thread Tools | Search this Thread |
| Display Modes | |
|
|
Linear Mode
