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› Regulator for 50 cents
11-05-2004 10:20 AM  13 years agoPost 1
Eytan

rrApprentice

Israel

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I ordered a 5V regulator from one of the model shops.
cost me 25 US$.
Out of curiosity I opened the shrink and found a single chip LM1085. Read its data sheet and it is 5v regulator 3A.
It has 3 legs +in + out and ground.
Went to an electronic shop and the D....thing cost 0.5 US$.

Bought a few .....
Is this a simple regulator or a good one?

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11-05-2004 01:59 PM  13 years agoPost 2
Jgiang

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Raleigh, the city in the park.... :)

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could you take a picture and post the picture. I want to see what 3 legs it used so that I can make one myself.

thanks,
JG


It was in the air, but now it's on the ground. :)

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11-05-2004 07:30 PM  13 years agoPost 3
Melnic

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Columbia, MD,USA

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You can get 5V low dropout regulators from http://www.digikey.com
If you look at the side with the writing on it, usually they are:
Left pin = voltage in
center pin = ground
Right pin = voltage out (5V)
you usually want both a 4.7 tantalum and a .1 ceramic capacitor on the output.
You trying to make a battery eliminator circuit?
Note that these need a heatsink if you are drawing alot of power from them. Keep an eye on the heat of this

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11-05-2004 07:45 PM  13 years agoPost 4
PaulH-MA

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Boston, MA

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If you're looking for more technical information about the LM1085 or sample circuit diagrams, you can look them up on National Semiconductor's web site:

http://www.national.com/pf/LM/LM1085.html

You may be more familiar with the LM317 voltage regulator. If you want to make your own 4.8v regulator to use with a Li-Poly battery as a receiver pack in you nitro/gas burning heli, you can use an LM317 pretty easily. They also make great glow plug ignitor circuits (1.2v)

http://www.national.com/pf/LM/LM317.html

--Paul

TREX 450
Bergen Intrepid Gasser x2

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11-05-2004 07:51 PM  13 years agoPost 5
MikeDD

rrApprentice

Elkhart, IN

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Note the LM1085 is an adjustable regulator(like the LM317) and is not the simple Vin-Gnd-Vout pinout of fixed regulators. The tab is Vout on this regulator(instead of ground). It requires 2 resistors to set the voltage.

Michiana R/C Choppers

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11-05-2004 08:15 PM  13 years agoPost 6
PaulH-MA

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Boston, MA

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Actually, National Semiconductor is making fixed voltage versions of the LM1085 in 3.3v, 5.0v, and 12v variations.

The whole point of using the LM1085 over the classic LM317 is that the LM317 requires between 1.5v and 2.5v difference between Vin and Vout for the regulator to be live. If you're stepping a 12v battery down to 6v, this isn't a problem. However, if you want to regulate two Li-Poly cells in series (approx 7v) down to 6v, you may have a problem, as there isn't enough voltage to keep the circuit alive.

The LM1085 has less than a 500mV difference between Vin and Vout under full load, making it useful in those situations.

--Paul

TREX 450
Bergen Intrepid Gasser x2

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11-06-2004 01:48 AM  13 years agoPost 7
Jgiang

rrVeteran

Raleigh, the city in the park.... :)

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what type resistor or capacitor should I get ? I want to make a 4.8 voltage regulator to use in the TX so that I can use battery that is more than 4.8volt in TX


It was in the air, but now it's on the ground. :)

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11-06-2004 02:21 PM  13 years agoPost 8
Gary Jenkins

rrElite Veteran

Nowhere, US

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Why not just use the 5.0 v instead of 4.8?

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11-06-2004 09:41 PM  13 years agoPost 9
Jgiang

rrVeteran

Raleigh, the city in the park.... :)

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Gary Jenkins
yeah, I guess it work too


It was in the air, but now it's on the ground. :)

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11-06-2004 10:10 PM  13 years agoPost 10
fitenfyr

rrProfessor

Port Orchard, Washington

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Diagram?
Ok so somebody show me the circuit for turning one of these into a 5V regulator for an Rx pack.

Might be fun to try a .50 fix from Rat shack to a 30.00 part.

Jason Stiffey
Fly Fast....Live Slow...

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11-07-2004 12:34 AM  13 years agoPost 11
PaulH-MA

rrVeteran

Boston, MA

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http://www.national.com/ds/LM/LM1085.pdf

Circuit diagrams start on page 7. Assuming that you can get all of the parts from DigiKey, you could probably build the whole regulator for less than $5.

--Paul

TREX 450
Bergen Intrepid Gasser x2

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11-07-2004 05:48 PM  13 years agoPost 12
Eytan

rrApprentice

Israel

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You don't need any resistors or parts.
The LM1085 IT-5 is set to 5V as is.
5V on the Rx works fine !!!!

Only need small heatsink.

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04-24-2005 02:04 AM  13 years agoPost 13
Jgiang

rrVeteran

Raleigh, the city in the park.... :)

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what happen if the input voltage drop below the regulated voltage. would the LM1085 bypass and put out the voltage the same as the input voltage?

eg.

thanks,
JG


It was in the air, but now it's on the ground. :)

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