Using resistor as voltage regulator

Hi,

I have a nice power source that provides me a steady 5v. I need to down this voltage to 3.3v and I know I can use voltage divider to that but wouldnt it be a good idea? I know a lot of power would be wasted as heat at the resistor, but should I worry with anything else?

I want to power an nrf24l01+ with 3.3v and I dont want to use voltage regulator and not buck converter either. Can I reliably use resistor to bring this 5v down to 3.3v? I will use decoupling capacitor of 10uF and 0.1uF in parallel with my nrf24l01+, do you think I will get a steady 3.3v this way?

It will give 3.3V but it won't give much current. Resistors are current limiting devices.

wouldnt it be a good idea?

It is a very bad idea.

I know a lot of power would be wasted as heat at the resistor, but should I worry with anything else?

The regulation. That is how the voltage output would change as the current drawn by your load changes.

Can I reliably use resistor to bring this 5v down to 3.3v?

No.

do you think I will get a steady 3.3v this way?

Absolutely no way.

I dont want to use voltage regulator and not buck converter either.

Shame about doing the project then.

So maybe I should use a voltage regulator. Do you know the difference of lm1117 and ams1117?

Same difference. Just made by different factories.
One might have better specs than the other, or one factory might exaggerate more than the other.
There are supply adapters for a nrf24L01 with the regulator and caps already fitted.
http://www.aliexpress.com/item/New-Hot-Socket-Adapter-Module-Board-for-8PIN-NRF24L01-Wireless-Module/1916191796.html
As already explained in your duplicate post, the 3.3volt of YOUR Arduino might be ok.

Leo..

Use one of these

Thank you all :slight_smile:

If you don't need much current, how about a simple emitter-follower? 5v to collector of an NPN transistor, a resistor from collector to base (size varies depending on spec, can try 10k), a zener diode that is about 3.9v or 4v in reverse bias from base to ground, and the output on emitter should be about 3.3v

common transistor like 2N3904 is probably good for a couple hundred mA before it becomes inefficient.

Quick and simple for small use and generally in small area.

Yourduino,com has a neat solution, little regulator board to plug the nrf24L01 module onto
http://yourduino.com/sunshop2/index.php?l=product_detail&p=487
Kit of two each and a spare transceiver, $10 for the 5 cards.

Can't beat those prices.

batata004:
So maybe I should use a voltage regulator.

As you've changed your stance on using a voltage regulator, I would say STOP and change your stance on a little widdy buck converter that you can pick up for about $2.00 / £ 1.50 and which gives you rock solid 3.3V at a magical 85%+ efficiency.

Linear voltage converters work by dissipating extra energy as heat, very wasteful and just feels 'wrong' in this day and age. Cheap, yes, easy to use yes, but poor technology - buck converters have all the advantages and none of the inefficiency.

Just as an example (I have no connection) see here ebay.com example

It's purely something I'm suggesting for you to consider (as you seem a bit indecisive :))

OK, now a few points here.

The example you cite specifies an output voltage of 1.8 to 2.6 V, so if that is correct, it would not be suitable for this application.

Also, the OP cites operating from a well-regulated 5 V supply. For dropping 5 V to 3.3 V, the efficiency of a buck regulator is not 85% and most likely no better than a linear regulator, certainly for such relatively low currents. It may also have a greater quiescent current.

Where the buck regulator is highly valuable however, is in deriving your 5 V or 3.3 V from 9, 12 or 24 V.

Just to clarify on the buck converter, the ebay example was an example of a Buck Converter and the price you might pay not a solution to this particular problem, I didn't even look at the voltage! :-[

As the OP was originally against all sorts of voltage conversion and had now changed his mind I thought it useful to suggest an alternative to a linear voltage regulator.

The question is really, why use a stable 5V supply if what you really need is 3.3V? In which case (as you mention) get a higher voltage adapter that would be much more useful in driving other (external) peripherals (9V or 12V) and also use a buck converter to get your 3.3V. Winner winner, chicken dinner.

Just suggestions!

If you have (sensitive) analog or RF circuitry, use a linear regulator, if digital or high power
(other than audio), a switchmode is fine. Analog circuitry needs clean voltage rails, switchmode
regulators do not output clean rails but have 100mV or more of noise and spurious signal. A linear
regalator's noise level is microvolts...

Sometimes you can get away with switchmode for sensitive analog, but that you would find out
by experiment (more modern SMPS using higher switching frequencies may be OK for audio where
the older slower ones were not, for instace).

You can also rigorously filter (LC pi filter and similar) switchmode rails to get much cleaner power too.

A single resistor will not regulate the Voltage down 3.3 Volts. Bad Idea :frowning:

If the load changes at the 3.3V side of things the Voltage Drop across the resistor will change,
and change the 3.3 Volts you are trying to create. (IE: no regulation take place)

One solution is to use a regulator IC, such as an LM-317.

This will allow you to set your desired output voltage, with proper regulation at its output.
An added bonus is it will take a wide range of input voltages as well.

If size is a consideration, use an LM-317T.

OKI Switchmode 3.3V , 1.5A regulator