If I put a atmega328p chip on a breadboard - to get 3.3v do I need to add a voltage divider from the source, eg 5v voltage regulator, to connect a 3.3v component? Would a 10k/20k voltage divider be the ticket? Is there a better way? The Uno has a 3.3v pin but I want to transfer my circuit to a circuit board.
So my circuit would have a wall 9v supply, one 5v voltage regulator and an additional voltage divider circuit to get the 3.3v?
Thanks.
You cannot use a voltage divider to power something, only to generate a reference voltage. (recall ohm's law, and imagine what would happen if the device you were powering tried to draw some current)
To get 3.3v if the Arduino is running at 5v, you need a voltage regulator.
An alternative, which might be more desirable, would be to run the whole thing off 3.3v. You'd probably want to run it at 8mhz (either off internal RC, or - preferably - an external 8mhz) - though people here seem to report that the 328p will run at 3.3v @ 16mhz even though it's not spec'ed for 16mhz below 3.7ish. Either way, running at 3.3 would also allow you to use a lower supply voltage, leading to higher overall efficiency - if you also have to interface with 5v devices, though, this isn't worth the trouble.
I'm running a TX so not sure what effect that would have on range if I lower voltage to 3.3v...hmmm...tried it at 3.3v just now...does affect range but may be able to live with it....
any recommendation for a 3.3v linear voltage regulator?...I'm using a L7805 now for 5v...
Thanks
What kind of transmitter? If you're talking about 433/315mhz ASK RF transmitter, the ones with the SYN115 chip on it are spec'ed for 3.3v operation.
7805's are primitive.
Look through these - pick one with the right headline specs you need, and sane price. Check the datasheets though - they may specify what kind of capacitors you need to use on the output (and sometimes the input) - some insist on tants, instead of lower cost ceramic or electrolytic caps.
For SMD applications, I default the ZLDO1117 series in SOT-223 (one of the nicer 1117-alikes that's still cheap), but that's not available in TO-220, and there are nicer ones in TO-220 anyway (it's easier to get heat away from a TO-220 than a SOT-223)
From other (locked) thread:
still searching for answer as research seems conflicting. The Tx component operates a minimum of 3.7v so I read although it seems to operate at 3.3v but at a much reduced range. I've ordered a buck converter but not sure if/how it will help. Is cheap enough though.
Seems that it would be a common problem though. Someone even suggested putting a red LED inline with the sensor as it drops the voltage 1.5v or so...
Newbie mistake. Apologies.
Buck converter is another way to lower voltage, and is perfectly good for producing 3.3v - though if I had a buck converter, and needed to run the chip at 5v and an accessory at 3.3 with a 9v wall supply, I'd use the buck to get 5v and run that through an LDO.
An LDO or linear regulator is smaller, simpler, and cheaper, but the output current is the same as the input current - but at lower voltage; that extra energy is dumped as heat. This makes linear regulators best suited to fairly light loads.
Buck converters are much more efficient - often 80-95%, so they don't waste as much energy as heat - but they're bigger, more expensive, and use more power under light/no load (quiescent current)