hi, im working on a project and i need a good "efficient" linear regulator. im going to be inputting between 6-9 volts and i need no less than 4.8v @1.5 amps. can anyone recommend a good regulator?!? thanks
Linear regulators are pretty much equally inefficient. They waste all unused power as heat.
If you are interested in efficiency, use one of these high quality buck regulators.
thankyou
notsolowki:
hi, im working on a project and i need a good "efficient" linear regulator. im going to be inputting between 6-9 volts and i need no less than 4.8v @1.5 amps. can anyone recommend a good regulator?!? thanks
Linear regulators are all equally inefficient to within < 1% or each other at that current level.
You haven't explained what you mean by "good", which might include any/all of:
low noise
high absolute accuracy
short-circuit-tolerant
good line-regulation
good load-regulation
low quiescent current drain
has enable input
wide operating temperature range
not picky about capacitor ESR
Linear regulators are all equally inefficient to within < 1% or each other at that current level.
Well, that is only true as long we are > Vout + Vdropout and we are drawing a non-negligible amount of current. After that, some regulators will be more efficient (even in the classical sense Pout/Pin) than others.
If we define efficiency a little less strict as "How long will my project run of a battery", it is even more complicated. If my battery voltage will go gclose to the optimal output voltage and below, linear regulator with high dropout will reduce the battery life because it will let Vout drop below the minimal voltage at an earlier stage. The project will not be able to use the battery charge efficiency.
If our project sleeps a lot, then quiescent current will become a factor, which again influences the mean efficiency. In those cases, most buck regulators are a terrible choice over an "inefficient LDO".
To choose an appropriate voltage regulator, find out:
- What will be the maximal current draw (and can you bring it down by adding caps, if they are only very short bursts, e.g. from an RF module)? (Most efficient-in-the-wider-sense-above regulators have rather low current ratings.)
- What percentage of time will your project sleep and thus draw the quiescent current? (This determines if quiescent current is a major factor.)
- What is the maximal and minimal voltage your project can safely work with, and what is the maximal and minimal voltage of the chosen battery pack during one discharge cycle? (This determines if Vdropout is a major factor.)
Go with the LT30XX series of Linear Technology.
notsolowki:
and i need no less than 4.8v @1.5 amps. can anyone recommend a good regulator?!? thanks
You really mean 'no less than'? Or do you actually mean 'no more than'?
To choose an appropriate voltage regulator, find out:
SagarDev:
Go with the LT30XX series of Linear Technology.
Yeah, sure, or just take some random device (which doesn't look like a good general recommendation).
Hi,
What is the application that you need the linear regulator for?
What are you using for your power supply?
Tom... 
Similiar question. I want to run a project with a stepper motor, arduino uno and A4988 motor driver. I prefer to use a single power source of around 20 volts. That will work fine for the motor and motor driver, but I need to drop the voltage to between 7-10V to use the Arduino VIN pin.
I think a voltage regulator should do the trick, but the heat generated might be excessive. So since the heat is a result of power dissipation, I should be able to get a handle on how hot it will become if I measure the current and voltage.
I thought about a buck regulator, but they are pretty expensive. I may be forced to go with a 9V battery to provide Arduino Power, but they are pretty short lived.
I will be driving the stepper motor for up to an hour at a time in a somewhat continuous cycle.
Any suggestions greatly appreciated.
ov10fac:
I thought about a buck regulator, but they are pretty expensive.
Less than $1 on ebay, including shipping to your door, is expensive?
Expensive/good ones are less than $5, and are as small as a finger nail.
Get a fixed voltage (5volt) one, and connect directly to the 5volt pin.
ov10fac:
That will work fine for the motor and motor driver, but I need to drop the voltage to between 7-10V to use the Arduino VIN pin.
No you do not!
The Arduino operates at 5 V. You need a 5 V "buck" regulator fed to the 5 V pin - and everything else that requires 5 V which may be substantial. The internal regulator on the UNO and the "barrel jack" are just incidental decorations. Powering those stepper drivers using the internal regulator on the UNO (or Nano) are common reasons for people to come back here for help.
Paul__B:
No you do not!
The Arduino operates at 5 V. You need a 5 V "buck" regulator fed to the 5 V pin - and everything else that requires 5 V which may be substantial. The internal regulator on the UNO and the "barrel jack" are just incidental decorations. Powering those stepper drivers using the internal regulator on the UNO (or Nano) are common reasons for people to come back here for help.
Thank you for your response but I think you misunderstood. I do not want to power the motor using the UNO internal regulator. I know that would be a fools errand. I want to power the motor and the UNO with the same external power supply, using a regulator to step down the voltage from the external power supply to 5 volts for the UNO operation.
Wawa:
Less than $1 on ebay, including shipping to your door, is expensive?Expensive/good ones are less than $5, and are as small as a finger nail.
Get a fixed voltage (5volt) one, and connect directly to the 5volt pin.
Well, that is pretty inexpensive. The ones I was looking at were a lot more than a dollar. Many thanks for the insight and source.
ov10fac:
I want to power the motor and the UNO with the same external power supply, using a regulator to step down the voltage from the external power supply to 5 volts for the UNO operation.
Ah yes, but you did say, did you not?
ov10fac:
I need to drop the voltage to between 7-10V to use the Arduino VIN pin.
Regulating to 5 V to power the UNO - via the 5V pin - is appropriate. Powering it via the Vin pin is not.
Paul__B:
Ah yes, but you did say, did you not?Regulating to 5 V to power the UNO - via the 5V pin - is appropriate. Powering it via the Vin pin is not.
Hmmm, there seems to be a disagreement on that. Everything I have read recommends against using the 5V pin because it is unregulated.
ov10fac:
Hmmm, there seems to be a disagreement on that. Everything I have read recommends against using the 5V pin because it is unregulated.
Wut? No, you are reading the wrong things, or not reading them carefully enough.
Using the 5 volt pin as in input, if you supply REGULATED 5 VOLTS, is a very good way to power an Arduino board. Do not put an unregulated voltage source into the 5 volt pin. If you have an unregulated voltage between 7 and 12 volts, then the VIN pin, (or the barrel connecctor of an Uno) is the best thing to use.
ChrisTenone:
Wut? No, you are reading the wrong things, or not reading them carefully enough.Using the 5 volt pin as in input, if you supply REGULATED 5 VOLTS, is a very good way to power an Arduino board. Do not put an unregulated voltage source into the 5 volt pin. If you have an unregulated voltage between 7 and 12 volts, then the VIN pin, (or the barrel connecctor of an Uno) is the best thing to use.
Ok, maybe this is old and superseeded, but this is from Arduino:
5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.
Regrettably, it has not been possible to edit and correct many nonsensical, counter-productive and possibly dangerous instructions in the Arduino documentation. (Well, dangerous to your Arduino at least!)
This is but one, and it continues to mislead the very novices it purports to assist. 
Now just for completeness, there is only one caveat regarding properly supplying the Arduino (Duemilanove/ UNO/ Nano/ Leonardo) with regulated 5 V via the "5V" pin.
It may just possibly be inadvisable to connect the USB cable for programming while the Arduino is powered from the "5V" pin.
The 5 V feeding back to the PC's USB port may in some cases, damage the USB port, although this is exactly what happens with the great majority of powered USB hubs, and most certainly all of the cheaper ones. 
So disconnect the connection to "5V" on the Arduino while programming.
ov10fac:
Ok, maybe this is old and superseded, but this is from Arduino:
It was never correct, even at the time of writing.
Mind you, Since the 3.3 V terminal is used for no other purpose than as a reference voltage for the op-amp, there never was any consideration of providing power to the Arduino in any manner whatsoever via that pin.