Hi,
I am newbie to arduino. I have a basic question.
I am powering the arduino with 9.2v li-po in DC barrel socket or vin . What would be the output voltage of digital pwm pins ? either 5v or 9.2v ?
5V. Basically the first thing behind that barrel socket is a linear voltage regulator that burn (literally, it is dissipated as heat) any excess energy that comes from a voltage larger than 5V.
Note that it NEEDS to burn at least 2V to work, thus the 7V minimal input power. Anything above that just makes the chip hotter.
Arduino's run on either 5V or 3.3 V depending on which one you are using.
Therefore the outputs would be either 5V or 3.3V as well.
A 9.2V Battery is a good choice because you will not run into voltage regulation problems when the battery voltage drops or sags after some use. Just don't let the pack voltage drop to low or you will permanently damage it.
As far as the "burn" or temperature of the regulator goes you won't have any issues with that unless you're really running a lot of higher current devices directly off the Arduino outputs. Each output is capable of 20 - 40ma maximum so you have to be careful what you run directly off each output as well. To run higher currents you likely wouldn't use a battery unless it's a high AH pack. You would want to power everything from a 9 or 12V Power Supply and use Transistors, MOSFETs, Realys or Drivers boards to drive your devices.
Well, it is questionable if the Arduino LDO (not: any LDO) is ever a good choice for serious battery operation ...
ElCaron:
Well, it is questionable if the Arduino LDO (not: any LDO) is ever a good choice for serious battery operation ...
Depends. If you need the higher voltage for something like motors, solenoids, or LED strips, it saves you having to built a boost converter into the circuit. Using a Pro Mini and proper power saving techniques in your code, the micro can run off of an obscenely low amount of current.
In fact I recommended exactly that for someone asking about designing a timed solenoid for use irrigating plants. Even though the solenoid would only be active for less than a minute a few times a day, the solenoid used about 1,000 times more energy (cumulatively) than I estimated the microcontroller + LDO would.
If you don't need higher voltage, get an 8 MHz Pro Mini and run it straight off of a 1S LiPo or 3x AA/AAAs. Also with power reduction techniques in the code. Most importantly, don't use an Uno, Nano, or Mega. They waste power like crazy.
technogeekca:
As far as the "burn" or temperature of the regulator goes you won't have any issues with that unless you're really running a lot of higher current devices directly off the Arduino outputs. Each output is capable of 20 - 40ma maximum so you have to be careful what you run directly off each output as well. To run higher currents you likely wouldn't use a battery unless it's a high AH pack. You would want to power everything from a 9 or 12V Power Supply and use Transistors, MOSFETs, Realys or Drivers boards to drive your devices.
Temperature's not the only concern. The heat generated by a linear regulator is wasted energy that could have been used to run your project longer. Once you get to above a few dozen milliamps or so, switching regulators will significantly improve your battery life.
Depends. If you need the higher voltage for something like motors, solenoids, or LED strips, it saves you having to built a boost converter into the circuit. Using a Pro Mini and proper power saving techniques in your code, the micro can run off of an obscenely low amount of current.
I cannot really think of anything where it depends. Note again that I was explicitly talking about the Arduino LDO with it's 2V dropout.
An LDO can be useful when the project sleeps a lot and the quiescent current governs the intake. But that would not be the Arduino's LDO. I like to use HT7333 for sleeping ESP8366, e.g..
If I need high voltages, I would go for a switching regulator. There are a few with very low quiescent current, even.
ElCaron:
Depends. If you need the higher voltage for something like motors, solenoids, or LED strips, it saves you having to built a boost converter into the circuit. Using a Pro Mini and proper power saving techniques in your code, the micro can run off of an obscenely low amount of current.I cannot really think of anything where it depends. Note again that I was explicitly talking about the Arduino LDO with it's 2V dropout.
An LDO can be useful when the project sleeps a lot and the quiescent current governs the intake. But that would not be the Arduino's LDO. I like to use HT7333 for sleeping ESP8366, e.g..
If I need high voltages, I would go for a switching regulator. There are a few with very low quiescent current, even.
You have a point there. The dropout voltage has nothing to do with it, but the quiescent current is terrible.
That HT7 part is definitely fine.
Boosting a lower voltage battery pack is definitely an option depending on circumstances. It wasn't very good for the irrigation project because the monstrous solenoid required so much power that battery life would be significantly reduced by using less batteries unless larger batteries were used (like D cells instead of AA). D cells are a bit more inconvenient than AAs, so a 6 cell battery of smaller cells was a better option than 2-3 larger cells.
I did recommend that in another project though. He was modifying an LED sign to flash patterns and it uses 3 AA cells. He decided to run the controller off unregulated batteries and use a boost converter to get 6.5V to run the LEDs from.
There is no one-size-fits-all power scheme. Careful consideration of all options is necessary.