Hello, on the Arduino UNO R3 and Mega 2560 R2/R3, there are 3.3V and 5V ports. How many sensors and circuits can these power ports support when they are used separately or at the same time?
How much current do your sensors and circuits require?
How will you be powering the UNO and Mega?
.
Hello, a battery holder for 2 AA batteries supply 3V and a much smaller coin battery such as CR-2032 and CR-2025 supply 3V. Are they good enough to provide power for breakout boards or sensors that require 3.3V? What are the disadvantages of using coin battery? How many breakout boards and sensors can they support?
During testing, I use a power supply. After testing, I plan to power the UNO/MEGA using 9V battery. If specifications are not given, how can I tell how much current the sensor/circuit require?
2 AA battery can supply ~ 2500mAH of current.
Coin cells are designed for slow trickle of current over long duration. So only 10s of mAH max, and only 200-300mAH total.
bbqq:
Hello, a battery holder for 2 AA batteries supply 3V and a much smaller coin battery such as CR-2032 and CR-2025 supply 3V. Are they good enough to provide power for breakout boards or sensors that require 3.3V?
That depends on the sensor in question. Look at its datasheet and see if it will run on 3V. Some will and some may not.
bbqq:
What are the disadvantages of using coin battery? How many breakout boards and sensors can they support?
How many depends on the current supplying ability of the particular coin cell you have in mind and the current requirements of the things that it is supplying.
You can measure what you are using with the power supply.
150mA is all you can get from the 3.3V supply, and 800mA from the 5V supply assuming no more than 7.5V into the barrel jack, and 800mA might overheat the regulator anyway. The 800 has to be reduced by the 3.3V current, the current for the 16U2, the current for the power LED, etc. So maybe 500-600 is available for offboard devices, reduced by the 3.3V current.
bbqq:
During testing, I use a power supply. After testing, I plan to power the UNO/MEGA using 9V battery. If specifications are not given, how can I tell how much current the sensor/circuit require?
Look at the datasheets for the sensors in question. Current requirements are always provided. If not, then choose a better sensor with a better datasheet.
Thanks. So, if possible, it is better to use 2 x AA batteries rather than coin battery due to the amount of current the battery can store.
If on the product information, it states that the circuit requires 3.3V, I better supply 3.3V rather than 3V? What is the best way to create 3.3V? 3xAA is 4.5V. The only solution I can think of is to use a voltage divider. However, I want to save breadboard space for other uses.
Many 3.3V devices actually require 3.0V to 3.6V. Read your datasheets carefully.
3.3V from <=3V can be efficiently created with a regulator like this one
Can't you use Arduino's 3.3volt supply.
Which Arduino are you using, and how much do you think the sensor(s) will draw.
You get a much better answer if you give us all the details.
Leo..
Please don't start two virtually identical threads 5 minutes apart. Wait to see what the answer to one gives, perhaps you can expand on your concerns there.
Threads merged.
bbqq:
If specifications are not given, how can I tell how much current the sensor/circuit require?
You have an ammeter? Measure it.....