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Robot needs power — Parallax Forums

Robot needs power

Ray0665Ray0665 Posts: 231
edited 2015-02-15 18:44 in General Discussion
I need to power a stock stingray msr1 board and a raspberry PI from a radio shack RC 7.2 V car battery
of course it must be mobile. Does anyone have a recomendation?

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2015-02-01 20:20
    I don't have the manual for the Stingray, but I believe it has a switching regulator and is designed to operate from a 7.2V supply, so it should be able to just be plugged into a 7.2V RC battery pack like the one from RadioShack. The Raspberry PI is designed to run off a 5V supply provided via a USB connector and draws anywhere from 1/2A to 1A depending on what's plugged into it. The 5V regulator on the MSR1 is capable of supplying 3A efficiently. Depending on what is plugged into the MSR1 and into the Raspberry PI, you might be able to power the PI from the MSR1. Dimension Engineering makes a 1A and a 3A 5V output switching regulator that could be used as an additional source of 5V from the 7.2V battery pack (http://www.dimensionengineering.com/products/de-sw050).
  • Duane DegnDuane Degn Posts: 10,588
    edited 2015-02-01 20:48
    I agree with Mike, the MSR1 should be able to supply enough current for the Raspberry Pi.

    I have several of the regulators Mike linked to and they work fine (though they do produce a lot of radio frequency noise). My main complaint about the DE regulators is the price. There are lots of switching regulators available which cost much less.

    Here's one.

    http://www.electrodragon.com/product/better-than-lm2596-dc-dc-step-down-adjustable-power-supply-module/

    If you don't want to wait for parts to arrive from China, I think you can probably find switching regulators for less than the DE one at Adafruit and SparkFun.
  • ajwardajward Posts: 1,130
    edited 2015-02-01 23:01
    Here's a link to the MSR1 data sheet. Perhaps this can give you an idea...

    http://www.mouser.com/ds/2/321/28230-PropellerRobotControlBrd-v1.0-10233.pdf

    Amanda
  • WBA ConsultingWBA Consulting Posts: 2,934
    edited 2015-02-02 01:22
    I have thought about switching my stingray setup over to the Elev-8 Li-Po pack since I already have one that gets little use: http://parallax.com/product/752-00010
  • Ray0665Ray0665 Posts: 231
    edited 2015-02-12 06:31
    Thanks for the replys.
    Powering the PI with camera was actually quite simple knowing that the MSR1 has the juice.
    I took a usb cord that my cat bit in half (I think someone put him up to it - below) put a 3 pin female
    servo connector on it plugged in to an I/O - and off she went.

    She was christened Rival by my wife. Turns out she thinks it is her rival for my time (and visa versa??)
    cant imagine how she got that impression...
  • ratronicratronic Posts: 1,451
    edited 2015-02-12 10:37
    Ray I hook up a jumper from the MSR1 power supplies directly to the Pi's GPIO's 5V & ground connections, do not know if this proper but it is how I've always done it.
  • Ray0665Ray0665 Posts: 231
    edited 2015-02-15 06:02
    Think twice about powering your pi thru the gpio pins. By doing so you are bypassing the fuze and protection diodes, the least little abnomaly on the power lines will bring out the magic smoke and the pi will dissappear. Having said that the msr1 regulated 5v is probably safe but....
  • ratronicratronic Posts: 1,451
    edited 2015-02-15 07:09
    I learned of unfused things and magic smoke years ago so I try real hard to stay away from the magic smoke.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2015-02-15 13:54
    Just to be clear, no one is powering a R Pi board through a GPIO pin right? You mean the 5V and ground pins which are on the header next to the general purpose input and output pins?

    Powering a R Pi with 5V on a GPIO has been shown to destroy the PI. (There are lots of dead R Pi boards for this reason.)

    http://www.raspberrypi.org/forums/viewtopic.php?p=576804#p576804

    IMO, the regulated 5V from the MSR1 board should be fine on the Pi.
  • ratronicratronic Posts: 1,451
    edited 2015-02-15 15:17
    Haven't destroyed one yet. It goes from the MSR1 Reg. 5V to the Pi's GPIO P1 pins 2 (5V) & 6 (gnd).

    Edit: After reading the thread you linked Duane I could see how people are destroying their boards.
    Several people in this forum have pointed out the error where you connect 5V to a GPIO pin.
  • Ray0665Ray0665 Posts: 231
    edited 2015-02-15 16:04
    Yessir them thar pins are the ones
    And after several days now powering the RPi from the MSR1 there are no issues. but for full disclosure I am powering thru the micro usb
  • ratronicratronic Posts: 1,451
    edited 2015-02-15 18:44
    I should also mention that the Pi on my Activitybot is wired the same way to the Activity board. I am not recommending this method of 5V powering of

    the Pi unless you know what you are doing and realize you are operating the Pi unfused. Since the Pi's GPIO's are 3.3V it is not a good thing to hook 5V to it.

    But after saying all that I have had no problems using the GPIO connector power pins to power the Pi's on both the Stingray and the Activitybot.
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