Powering gopigo3 from a wall powesupply?

[pitosalas]

Is it possible to power the RasPi and GoPiGo3 using a micro usb plugged into the Raspi? Is it a good idea? What are the tradeoffs?

[kev.r]

From a past thread about this question:

Can we power gopigo3 via pi?

Hello @chetuk The motors require more than what the Pi can offer. You can read sensors, control the LEDs but you can’t power the motors without the battery pack. Cleo

I use a 12v 3a power adapter plugged into the power connector on my GoPiGo3 board when I’m programming and don’t mind having it tied to a power cord. This has worked well for me.

-Kevin

[pitosalas]

Thanks but that wasn’t what I was asking. I am asking whether powering the gopigo3 by means of the Pi is ok… Because my wall power supply has a micro-usb which plugs nicely into the Pi. But when I did that the light on the gopigo3 did a blinking red thing which I hadn’t seen before.

[kev.r]

I’ve seen a few questions on this topic in the past.

All the answers I’ve seen say that powering the GoPiGo3 from the Pi (via the micro usb connector) does not supply enough power to run the motors.

more info here:

Minimum voltage needed to drive motors?

The problem with powering the GPG robot with running motors (any version) with only USB power, is that the motors can cause dips or “brown-outs” on the 5v power supply rail. If the Raspberry Pi doesn’t have a well-regulated 5v power supply, it can crash and/or corrupt the SD card. To prevent people from running the GPG without batteries, there is a software safety that prevents the GPG3 motors from running when there is inadequate power (batteries not connected). The GPG2 and GPG3 use very simi…

-Kevin

[jimrh]

@pitosalas

Is it possible to power the RasPi and GoPiGo3 using a micro usb plugged into the Raspi? Is it a good idea? What are the tradeoffs

Since I have done a considerable amount of research on this topic, (make that read “I’ve been a pain and asked a lot of stupid questions”), here is what I’ve learned:

1. You can power the GoPiGo’s logic and anything that doesn’t require power from the GoPiGo board itself. (i.e. WiFi, sensors, etc.)

2. Anything that requires actual power, like the motors or servos won’t work without a battery attached.

Tradeoffs:

1. If you’re doing something that doesn’t require battery power, (no motor or servo use), running off of “ground power” with the batteries disconnected will extend your battery life because you aren’t using them.

2. If you are working on something that does require power, but you can avoid motion, (by lifting the robot off its wheels, unplugging the motors, or turning it upside down), using both wall power and battery power together works well since you are mainly using the batteries for the higher current needs.

3. Doing development work on the 'bot, only using battery power can deplete them rapidly.

Important Caveat:
Once a battery is attached and the GoPiGo senses it, (i.e. the power LED goes green), removing battery power does not reset it!  In other words, if you have both wall and battery power applied, and then remove the battery, the GoPiGo will act as if the battery is still attached.  (IMHO, a firmware bug)

This is especially important if you inadvertently do something that requires the wheels to move - the 'bot will run off while still attached to the wall!  (Ask me how I discovered that little fact!)

There is also the possibility of “browning-out” the GoPiGo due current draw if the wall adapter can’t handle the load.

Additionally, if you use the GoPiGo’s power button to shut down, you should disconnect wall power first.

Cute hack:
Several companies sell a pass-through switch adapter for the Pi that allows you to turn on and off the wall power without having to continuously insert and remove the connector.  I bought a few and they’re worth their keep.