Let's Make Robots!

Quick question - voltage regulators in parallel (sorta)

I have a 8.4V 2/3A 1100 mAh NiMH battery from an airsoft gun (charger was included!) and I read that the raspberry pi and most USB devices tolerate only up to 5.25V (okay I guessed 8,4 was way too much). I need to regulate it to 5V. I thought of using a low-dropout voltage regulator, but the shop nearby only seems to support voltage regulators of a max of 1.5A. I have calculated that my robot can have 3A surges if all systems are on and the motors are stalling (extreme scenario, but it might happen). So with that in mind, is it possible to just add two of the voltage regulators, one lets say for the Pi and USB stuff, and another for the motors, the Arduino and LED + buzzer? To my understanding it should work, but I'm no expert and I don't want anything to blow up. No magic smokey. 

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Don't forget to tie the grounds together. :)

As bdk6 pointed out, a seperate regulator for the Pi is a good idea.

Poor efficiency and heat will be the biggest problem. You really want a switchmode regulator.

Yeah, switch mode regulators are cool. http://www.pololu.com/catalog/product/2177

Thanks for pointing that out! 

I really like the voltage regulators from http://www.dimensionengineering.com

I bought several of these: http://www.dimensionengineering.com/products/de-swadj3 for regulating power to motors or other "big" consumers (it could also easily power a PI and an USB hub)

And some of these http://www.dimensionengineering.com/products/anyvolt-micro, for powering arduinos from either 1 LiPo or 3-4 NiMH cells.


Oh well, seems like I have found it. 3V <= Vin - Vout <= 35V and 3A max. Silly me. For the record though, would my original solution have worked?

Can you post a schematic of what you're imagining?  My instinct is that with what I think you're describing is that you should be okay, especially if you use snubbers to capture the transients across the vReg.  "Current is drawn, not pushed" was the way my highschool electronics teacher used to put it.  If you isolate the pi from the motors using a regulator, my instinct is that it wouldn't be affected, but I'd wait for BDK6 or DanM to weigh in on this.


Battery----voltage regulator----Pi

                        |                                                   I'm just imagining 3 branches like this, or something roughly along these lines

                        \                                                      I too am thinking that if each of these 3 branches draw lower then 1.5A, then

                           \                                                          the individual voltage regulators should do fine. It just sounds too good to

                                ----    Arduino and other systems              be true.


                               --------- Motors (400mA stall each of the two- that's okay)

My ASCI art didn't get through...