I'm planning to use two 2.8" Touch-LCDs to display some information - text, no graphics.
As far as I understand it the LCDs are equipped with a cpu theirselves, so I don't need much compute power at the arduino's end.
I want to build a battery-saving system - so what is my best pick here? The LCDs use 3.3V but can operate with 5V too.
I was thinking about an Arduino Pro Mini - would 8 MHz be enough to drive those LCDs?
Where can I find the standard power consumption (idle/work) of all Arduinos?
Each pin on an Arduino can only give (roughly) 20mA... some say up to 40mA max..
With a total or around 100-150mA or so I have read for the whole board. (limit)
You generally do not use the Arduino to 'drive' anything outside of simple accent leds..etc
xl97:
Each pin on an Arduino can only give (roughly) 20mA... some say up to 40mA max..
Read the data sheet of the ATmega328 processor: it can produce 20 mA per pin continuous, absolute maximum rating is 40 mA.
With a total or around 100-150mA or so I have read for the whole board. (limit)
That depends highly on how you power the board and how you draw the power from the board.
justmee:
I want to build a battery-saving system - so what is my best pick here? The LCDs use 3.3V but can operate with 5V too.
A barebones ATmega processor. Use the Arduino board for prototyping, then the final project on just a processor with minimal peripherals. Use the sleep modes for additional power saving.
Note that LCD screens themselves tend to use so much power that the savings by not using a development board may be negligible. A Pro Mini board has the fewest extra components (do get rid of that power LED) so will give you the easiest route to a low power system.
wvmarle:
That depends highly on how you power the board and how you draw the power from the board.
Afaik I can connect the LCDs to 3.3V directly without a problem.
A barebones ATmega processor. Use the Arduino board for prototyping, then the final project on just a processor with minimal peripherals.
If I just use the ATmega I will have no power regulator, right?
Use the sleep modes for additional power saving.
Are you referring to ATMega or LCDs here?
A Pro Mini board has the fewest extra components (do get rid of that power LED) so will give you the easiest route to a low power system.
That was my thinking.
Note that LCD screens themselves tend to use so much power that the savings by not using a development board may be negligible.
Mhh I read that they use less power than 7-segment-LEDs, that's why I went for this approach. Unfortunately I can't find any information about power consumption in the data sheet
Do you have some circa numbers for me?
justmee:
If I just use the ATmega I will have no power regulator, right?
Of course. You have to add all those bits yourself if you need it.
No idea how much power your display uses; just measure it. Keeping the backlight off wills ave a lot of power as well. The data sheet mentions sleep modes (I was talking about the processor itself), so that should be able to save some more.
Slow down justyoo! Can yuo show us a link to the LCD modules you plan on using? I suspect the 328 it's talking about is built into the device, and that it communicates with your Arduino by some other means, such as serial or I2C. If so, you won't need to worry about the internals of the device at all.
wvmarle:
Read the data sheet of the ATmega328 processor: it can produce 20 mA per pin continuous, absolute maximum rating is 40 mA.
Whats the difference from what I stated? Because I said 'some say' 40mA max ? Whats your point:? (not snarky, seriously,, what are you trying to point out about my comment?)
There are many posts saying that 40mA is not even good to do (while others say its fine,.. 'its just a max rating')
It is not "some say can do" . It's the manufacturer specified absolute maximum rating as stated in the data sheet. That's the difference. Rumour vs. fact.
An absolute maximum rating generally means that it can be done for short periods of time, but not continuous - though that may work, with enough cooling, or when you're plain lucky with your part. The 20 mA rating is guaranteed to work for continuous use.
wvmarle:
No idea how much power your display uses; just measure it. Keeping the backlight off wills ave a lot of power as well. The data sheet mentions sleep modes (I was talking about the processor itself), so that should be able to save some more.
I'd measure it, but I'm still in the planning phase, looking for the best solution.
ChrisTenone:
Can yuo show us a link to the LCD modules you plan on using? I suspect the 328 it's talking about is built into the device, and that it communicates with your Arduino by some other means, such as serial or I2C. If so, you won't need to worry about the internals of the device at all.
wvmarle:
It is not "some say can do" . It's the manufacturer specified absolute maximum rating as stated in the data sheet. That's the difference. Rumour vs. fact.
An absolute maximum rating generally means that it can be done for short periods of time, but not continuous - though that may work, with enough cooling, or when you're plain lucky with your part. The 20 mA rating is guaranteed to work for continuous use.
Fair enough... but as you even state yourself..
"but not continuous - though that may work"..
Which is why my words were chosen. Some say it is safe to do so.. others say it not very safe to pull 40mA from a single pin.
So if the datasheets says so.. 'may' is not very factual.
Perhaps I should have said 'same say'...... followed by 9but not recommended)