Flora - VBATT - Not per description!

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davidhaile
 
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Flora - VBATT - Not per description!

Post by davidhaile »

I bought two Flora's and Neopixel strips and misc to build the Firewalker shoe project with my teenager daughter. After much fussing with the driver and Adafruit's Aduino IDE v1.6.4, we had some success programming one Flora and playing with it yesterday evening. We had two meters of Neopixel strip on it - possibly too much current. This afternoon I couldn't get that Flora to run. I switched to the 2nd Flora that doesn't have the Neopixel strip connected and all is well.

I probed around and was depressed to find 5V on the VBATT pin when the switch is OFF. The 5V is coming from the USB connector's 5V so it has a maximum current draw of 500mA. This means there is no safe way to have the whole Neopixel strip connected while I'm trying to program the Flora. I'm sure we popped L1 on the first Flora. Send me a part number (I can also find an equivalent) and I'll order some replacements. We have a 60 LED strip which could draw over 1A. I'll cut the strip in half and continue the project for now.

I suggest a design change to the Flora such that a high current load on the VBATT pin is not connected to the host computer's USB 5V. It can work the way it is designed but the possibility of blowing L1 is not obvious from either the example projects or from description of how the VBATT pin should be used. Many users do not understand a schematic.

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adafruit_support_mike
 
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Re: Flora - VBATT - Not per description!

Post by adafruit_support_mike »

It's normal to see 5v (or slightly less) on VBATT when the power switch is turned off. The VBATT pad is connected to 5vUSB through a Schottky diode. Only the power from the battery is controlled by the switch.

The L1 fuse prevents loads that want more than 500mA from overloading the 5vUSB line. If the fuse is blown, its resistance will be very high, and you won't see 5v on VBATT.

Post a photo showing your hardware and connections and we'll see if we can find any trouble spots. 800x600 images usually work best.

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davidhaile
 
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Re: Flora - VBATT - Not per description!

Post by davidhaile »

I've attached it exactly as suggested in the Firewalker tutorial. I was incorrect in something I said previously. We connected the entire 2 meter Neopixel string which can be 2A if all LED's are ON. Isn't it true that the VBATT pin shares the USB 5V input? I understand how it works well if USB is not connected and that it also works well if it isn't trying to drive 120 Neopixel LED's. The problem is when it is trying to do both.

On the other hand, now that I've realized that we had 120 LED's connected, it sure could have taken out that FET.
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adafruit_support_mike
 
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Re: Flora - VBATT - Not per description!

Post by adafruit_support_mike »

A NeoPixel strip doesn't draw any noticable current when the LEDs are off. Each LED can draw up to 20mA, for an upper limit of 60mA per pixel, but in practice you'll only see that much load if the whole strip is running 100% white.

What resistance do you see across L1?

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