Power for sensors

I have one QTR-8RC digital reflectance sensor array (cut down to 6) and 3 GP2D120 Sharp analog distance sensors that I need to power. The operating voltage for the Sharp sensors range from 4.5v to 5.5v each and I would like to use the 5v option with the QTR. My micro controller is only 3.3 volts, I tried using the Pololu 5v booster regulator on the Sharp sensors, but the readings were way out of whack when compaird to giving them a standard 5v. I have not had a chance to test out the QTR yet, but I am sure that I will run into the same problem. I am already using 3 lipo 3.7v batteries for several motors and to power my micro controller. What options do I have to power these four sensors? One more battery will not provide enough voltage and I am not sure there is room for 2 more batteries and a step down reglator as I am trying to keep the weight down.

I am open for feedback or ideas.
Sorry, I posted this in the wrong section.


Your talk of five batteries makes It seems like you might not realize that you can create multiple power rails from a single battery pack. If you are using two LiPos in series for your motor batteries, then you can also use that to power a 5 V regulator for your 5 V parts and a 3.3 V regulator for your 3.3 V parts.

Are you running your MCU off of one of your LiPos directly or are you using a 3.3 V regulator?

It should be fine to run the QTR-RC sensors at 5 V since the sensors will not output more than the voltage you use to charge the output node (which is whatever voltage your MCU is running at). You will need to power your Sharp distance sensors at 5 V, but you can still likely connect the outputs directly to your MCU as the sensor outputs don’t get much above 3 V.

How does “a standard 5V” differ from the output of the 5V boost regulator? Did you verify that the regulator was actually outputting 5 V? The Sharp distance sensors draw power in bursts, so adding some capacitors to the boost regulator output might help.

I think that in your place, my approach would be to use two LiPos in series to power the entire system, including regulators like a D15V35F5S3 or a D24V6ALV that then supply the 5V and 3.3V power rails required by the sensors and microcontroller.

- Ben

Hi Ben, thanks for all your help. I have a lot to learn about voltage and the best metholds to connect things. I did verify the 5v booster was outputing 4.8v to the sensors. Let me expaine my connections:
(3 lopo batteries, 6 motors, one Arduino fio,4 sensors, 1 5v booster, and 1 2.5v-9.5v booter)

I have one lipo 3.7v battery powering an Arduino FIO all by itself.

I have two lipo batteries combined that output 3.7v x2 = 7.4v volts powering the Motors with the Pololu 2.5 -9.5v adjustable boot regulator outputting a little extra 9.3v. We discussed this on another thread, I am going to try it out with direct power from the batteries tonight.

From the Arduino FIO 3.3v out I am going to a 5v boost regulator to power the power side of the motor controller and to power all 4 sensors. When I try this out, I the motors wont work because I think the power to the motorcontroller drops below the requied voltage.

So based on your last comment, I should power everything from the batteries and use regulators to step down to the voltage that I need. Question, if I power 4 things that need 5v from a 5v battery, will all 5 things recieve 5v until the battery looses power?