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Powering the Feather MO Express with 6V through JST connecto
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Powering the Feather MO Express with 6V through JST connecto

by martian on Sun Feb 11, 2018 4:30 pm

So I have two questions actually.

First, I'm thinking it is Ok to use the boards JST connector to 4 AA batteries. The voltage regulator can handle 6v input, shouldn't it?

Secondly, I have this connected to the 8-Channel Servo FeatherWing. Any problem with powering this board off of the same 4-AA batteries as are running the Feather above? I figure since the 2 standard servos are drawing their power from the servo board and not THROUGH the Feather M0 itself, this is OK. Does that sound right?

Thanks!

These are the two products in question:

https://www.adafruit.com/product/3403
https://www.adafruit.com/product/2928

martian
 
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Re: Powering the Feather MO Express with 6V through JST conn

by adafruit_support_mike on Mon Feb 12, 2018 6:29 am

The voltage regulator can handle 6V, but the LiPo charger can't. The highest voltage you can connect to a Feather is about 5.5V.

There are also some issues with the exact battery voltage. Alkaline cells usually start around 1.7V when they're new, and drop to 0.9V when they're about 95% drained. A 4-AA pack with new batteries would be closer to 6.8V than 6V.

You'll need to drop the pack's voltage to a level the Feather can handle. A small 5V regulator will do the job:

https://www.adafruit.com/product/2236

Running the servos from the same battery pack that powers the Feather is okay. In general, it's safe to connect two loads to the same power supply. You just don't want to connect two power supplies to the same load unless they're designed to work together.

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Re: Powering the Feather MO Express with 6V through JST conn

by martian on Mon Feb 12, 2018 11:52 am

Thank you! I appreciate the advice.

So a quick follow-up: after I posted, I went ahead and tried anyways. It seemed to work. I only had it connected for about 30 seconds, but now I’m worried about my lipo charger. My batteries were outputting 6.2v. Is there a quick way to test if the charging still works? I won’t obviously need this in the current setup since it can charge the 4aa batteries, but would be good to know.

martian
 
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Re: Powering the Feather MO Express with 6V through JST conn

by adafruit_support_mike on Tue Feb 13, 2018 3:15 am

The easiest way to test the charger is to plug in a LiPo and connect the board to a USB cable.

If the board still works, best of luck to you. It's operating outside the specified range, and is in "you're on your own" territory.

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Re: Powering the Feather MO Express with 6V through JST conn

by martian on Tue Feb 13, 2018 4:48 am

Cool. Thanks again!

martian
 
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Re: Powering the Feather MO Express with 6V through JST conn

by martian on Tue Mar 13, 2018 3:26 pm

Hey Again,

Hoping to follow up on this, now that I'm actually trying to build this out. I'm having trouble with the servos. I purchased the voltage regulator recommended and capacitors that the voltage regulator page called for (10µF electro). Seems to work ok with the micro servos I tested with before, but the full size servos I intend to actually use act erratically, moving somewhat on their own and making whining noises.

the servos are like these, but without the "R" in the name (i.e Tower Pro MG995 vs MG995R):

https://www.adafruit.com/product/1142

Is it perhaps that 4AA can't provide the current these bigger servos need? Or is it that they draw enough current that I need a capacitor added to my feather servo board? My project uses two of these servos.

When I power the servos independently with Adafruit's 5V 2 A power supply, it works fine(without above proposed feather capacitor added), so I know the servos are not bad.

I appreciate any input.

Marty

martian
 
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Re: Powering the Feather MO Express with 6V through JST conn

by T_Mo on Sun Mar 18, 2018 12:16 am

I don't think the AA batteries can supply enough current to run the servo motors.

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Please be positive and constructive with your questions and comments.