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This Instructable will show how to Make a 1.6v-6v Filtered Linear Power Supply using a LM317 for the variable voltage regulator and a 1kohm Potentiometer (trimmer). It can source power from anywhere between 7v to 14v for this version of the power supply. The power supply in the above image is at the top and you can see a 7.4v battery plugged into it, with a 3.3v cable harness attached to the output on the right of the power supply.
Filtered means that it is good for sensitive IC's as it will provide the most accurate selected voltage possible. This is accomplished by using filter/bypass/decoupling capacitors on the power rails to reduce noise. This power supply can source power from a range of power supplies within 7-14 volts @ 500ma. The lm317 can sink more than 500ma of current but at the sacrifice of having to use a lower voltage, this is because the LM317 has a max rating of 3watts total. Sinking 1.5 watts of power uses a fair size heat sink so if you want to have more power running though it you may want to move to a larger Voltage regulator.
This power supply is not suited (or needed) to power standard MCU's like the arduino uno or mega. It works great with a few tweaks to power a stand alone or breadboarded ATMEGA328 though, because the power is filtered and you have a nice easy way to adapt it to the same sources the standard arduino's use. Just beware that the ATMEGA328 is capable of drawing up to 560ma with just it's digital pins and this will stress the heck out of the power supply.
Filtered means that it is good for sensitive IC's as it will provide the most accurate selected voltage possible. This is accomplished by using filter/bypass/decoupling capacitors on the power rails to reduce noise. This power supply can source power from a range of power supplies within 7-14 volts @ 500ma. The lm317 can sink more than 500ma of current but at the sacrifice of having to use a lower voltage, this is because the LM317 has a max rating of 3watts total. Sinking 1.5 watts of power uses a fair size heat sink so if you want to have more power running though it you may want to move to a larger Voltage regulator.
This power supply is not suited (or needed) to power standard MCU's like the arduino uno or mega. It works great with a few tweaks to power a stand alone or breadboarded ATMEGA328 though, because the power is filtered and you have a nice easy way to adapt it to the same sources the standard arduino's use. Just beware that the ATMEGA328 is capable of drawing up to 560ma with just it's digital pins and this will stress the heck out of the power supply.
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So there are two ways of going about this. The totally home-brew way, or the lame way where you just go out an buy a 5v/3.3v power supply . There are lots of different kinds of these available but the one from SparkFun is great because you support a great company and it's breadboard compatible (awesome!).
For those of you who want to build it yourself AND save yourself a few bucks then that's what you'll learn to do. Lets start with the parts list:
1x protoboard - doesn't really matter what size as long as you can make it fit. 2"x2" should be fine but the heat-sink will likely hang off the edge unless you're creative
1x LM317 (type-t) Variable voltage regulator
1x heat-sink capable of dissipating up to 3 watts.**
1x 1N4001 1A Diode
2x 3.5mm pitch 2-pin screw terminals*
2x Break Away Headers* - (Right Angle or Straight depending on your design)
1x 100uF electrolytic radial capacitor
1x 10uF electrolytic radial capacitor
1x 0.10uF ceramic disc capacitor
2x 330ohm 1/4W 5% Carbon Film Resistors (standard resistors)
1x 1k ohm adjustable Potentiometer/Trimmer.
1x LED 5mm (your choice of color [may need to adjust resistor value])
Some wire - 22 gauge.
note - you'll also want to have some thermal compound handy for the heat-sink.
*The headers and screw terminals are how I decided to attach my power source. My supply is set up to accept power from either the screw terminals (from a 9v battery lead) or directly from a 7.4v 1600mah battery pack. These can be adapted however you want and I would suggest adding a 2.0mm DC Power Male PC Mount (2-pin) if you want it to work with a 9-12v wall transformer. That way it has a nice clean interface and you cant mess up the polarity.
** The heat-sink is important and there are several different ways to go about using it. The heat-sink is for the LM317 voltage regulator, it needs to be sinked for our purposes and while a 1.5 watt heat-sink is what i'm using and does a fine job for what i use it for, if your dropping a lot of power and using a lot of current you'll want to consider using a larger one. Just remember that this specific voltage regulator only supports up to 3Watts total even WITH the heat-sink.
It seems like a lot, but the total cost for just about everything here is less than $5 when ordered online. You can still get most of the parts from local hobby shops (or radio shack) for less than $10 and i'm sure if you've been working with electronics for a bit now you'll have most of these parts on hand anyways.
For those of you who want to build it yourself AND save yourself a few bucks then that's what you'll learn to do. Lets start with the parts list:
1x protoboard - doesn't really matter what size as long as you can make it fit. 2"x2" should be fine but the heat-sink will likely hang off the edge unless you're creative
1x LM317 (type-t) Variable voltage regulator
1x heat-sink capable of dissipating up to 3 watts.**
1x 1N4001 1A Diode
2x 3.5mm pitch 2-pin screw terminals*
2x Break Away Headers* - (Right Angle or Straight depending on your design)
1x 100uF electrolytic radial capacitor
1x 10uF electrolytic radial capacitor
1x 0.10uF ceramic disc capacitor
2x 330ohm 1/4W 5% Carbon Film Resistors (standard resistors)
1x 1k ohm adjustable Potentiometer/Trimmer.
1x LED 5mm (your choice of color [may need to adjust resistor value])
Some wire - 22 gauge.
note - you'll also want to have some thermal compound handy for the heat-sink.
*The headers and screw terminals are how I decided to attach my power source. My supply is set up to accept power from either the screw terminals (from a 9v battery lead) or directly from a 7.4v 1600mah battery pack. These can be adapted however you want and I would suggest adding a 2.0mm DC Power Male PC Mount (2-pin) if you want it to work with a 9-12v wall transformer. That way it has a nice clean interface and you cant mess up the polarity.
** The heat-sink is important and there are several different ways to go about using it. The heat-sink is for the LM317 voltage regulator, it needs to be sinked for our purposes and while a 1.5 watt heat-sink is what i'm using and does a fine job for what i use it for, if your dropping a lot of power and using a lot of current you'll want to consider using a larger one. Just remember that this specific voltage regulator only supports up to 3Watts total even WITH the heat-sink.
It seems like a lot, but the total cost for just about everything here is less than $5 when ordered online. You can still get most of the parts from local hobby shops (or radio shack) for less than $10 and i'm sure if you've been working with electronics for a bit now you'll have most of these parts on hand anyways.
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Something like this but go bigger on the pass transistor. I think a 2N3055 can push 10 amps.
Oh another thing for higer amp u can use power transistors with lm317