SparkFun Forums

[shawnd]

Hi,

I am new to MCUs and in the process of designing a home sensor for temp/humidity/water detection. To get started, I decided to tackle the first problem: getting a steady supply of power to the breadboard. It all works in real life but wanted to also start designing the schematic for it as it will be needed once I get to PCB design for the whole sensor unit.

The design is based on reading about SparkFun's power supply kit as well as a few other tutorials and youtube videos. Eventually, the system will be powered by a 9v battery (instead of converted DC from the wall) and output 3.3V. This schematic will be part of a larger schematic which would include the sensors, MCU, etc.

Would appreciate if anyone could provide any feedback on the schematic. I understand its pretty simple, but are there better design practices that I could follow? Should I have multiple GND or have those be connected to the same? Should I extend out a GND connecter? Good reading on the topic?

Thanks,
Shawn

[Ross Robotics]

A 9V battery will not last long in any project. It just doesn't have the capacity.

You don't have to worry about using multiple GND symbols on the same block as they will all be connected on the PCB. Same goes for VCC.

Everything looks ok though. Just make sure the regulator can supply enough current for the circuit.

[shawnd]

Thanks for the feedback.

I would prefer to go the battery route as otherwise I have to run new electrical wires in the crawlspace ($$$$). Once the project ( https://forum.sparkfun.com/viewtopic.php?f=4&t=42910) is near completion, I can probably run a few tests to determine an average daily power draw to estimate battery life. If it's in the few months, that would suffice. Specially if I can build in a battery power level circuitry and alert if it drops below a certain threshold.

[Ross Robotics]

Never said to hard wire it into mains. Think about using AA's or even C or D batteries and will last for months.

[shawnd]

Ah - incorrectly assumed you were referring to batteries in general. Can you explain why the difference in longevity between the two types?

[Ross Robotics]

mAh - milliamps per hour. A battery only has so much energy capacity. Other than that, you can do a Google search about the basics of batteries and ohm's law. It has been written many times and will take a while to retype it.

[shawnd]

Yep - sorry went to google and found the answer. Would be interesting to see how much current the finished circuit draws and then its a decision between size and frequency of heading down to the crawlspace