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Feather HUZZAH with ESP8266 WIFI board maximum supply voltag
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Feather HUZZAH with ESP8266 WIFI board maximum supply voltag

by danleeson on Tue Nov 01, 2016 12:20 pm

Hi, I'm trying to control other consumer electronic with my Feather HUZZAH over WIFI.
This device, while powered off, has 12V and ~7V rails on standby from the DC power supply, but nothing lower. I was wondering what is the maximum safe supply voltage for the feather, when it's connected to USB 5V +power rail. I couldn't find this info on Feather specs.

I'm short on space and I want the board hidden inside the mother device's chassis, so I do not want to use LiPo battery option. If feather's USB port could take 7~8V as input it'd be great. Otherwise, I'll have to add another regulator:(

Thanks,
Dan

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Re: Feather HUZZAH with ESP8266 WIFI board maximum supply vo

by clemens on Wed Nov 02, 2016 8:38 am

I'm searching for the same information but for the Adafruit HUZZAH ESP8266 (no Feather, the version without USB). I think there was a wrong label on the first version. e.g. https://cdn.shopify.com/s/files/1/0320/ ... 1444152617

V+: 3.5-16 (!!) VDC
VBat: 3.5-16 VDC

on the backside of the second version is printed now:

V+: 3.5-6 VDC
VBat: 3.5-6 VDC

So the same range for V+ and VBat

On some reseller pages you can read 2 x 3-12V, now on Adaruit you can read: 2 x 3-6V power inputs

What are the right numbers? Is it ok to run the Huzzah with 4x AA that means with full batteries 6V+ or with 9 or 12 V battery input?

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Re: Feather HUZZAH with ESP8266 WIFI board maximum supply vo

by adafruit_support_mike on Thu Nov 03, 2016 2:19 am

We suggest staying between 4v and 6v for both of them, but for different reasons.

The Feather HUZZAH's power goes through an MPC73831 LiPo charger before it reaches the voltage regulator. Voltages higher than 6v can kill the MCP73831.

The HUZZAH breakout uses a voltage regulator that can handle input voltages up to 16v, but it's a linear regulator. It burns off the difference between the input voltage and output voltage as heat. The ESP8266 uses a lot of current, and for that load, the heat dissipation reaches the regulator's limit at a supply voltage of about 6v.

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Re: Feather HUZZAH with ESP8266 WIFI board maximum supply vo

by danleeson on Fri Nov 04, 2016 12:17 am

Thank you. That helps a lot.

I haven't looked at the schematics, but based on what you said about power going through LiPo charger, I assume if I hook it up to voltages higher than 6V, it can kill the charger, cutting power to the voltage regulator; correct?

Also, this just occurred to me (kind of off-topic), but is there a way to program the ESP8266 to use less power by trading off WIFI range?
Actually, I haven't done any searches on this yet. I'll come back after doing some preliminary research
.

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Re: Feather HUZZAH with ESP8266 WIFI board maximum supply vo

by adafruit_support_mike on Sun Nov 06, 2016 1:54 am

danleeson wrote:based on what you said about power going through LiPo charger, I assume if I hook it up to voltages higher than 6V, it can kill the charger, cutting power to the voltage regulator; correct?

It's a little more involved than that.

Power from the USB jack goes to the LiPo charger and the voltage regulator. The output from the charger goes to the battery (obviously), and then through a diode to the voltage regulator. If the voltage at the USB jack is higher than the battery voltage, the diode will be reverse-biased and cut the battery and LiPo charger out of the circuit feeding the regulator.

OTOH, killing the LiPo charger would probably create a short to GND, so all the current from the USB jack would be flowing through that path rather than going to the regulator.

In the event of a chip failure that didn't produce a short, the board would continue to work as long as power was connected to the USB jack, but would stop as soon as USB power was disconnected. There's no such thing as a chip failure with well-specified performance though, so a failure that doesn't initially create a short can evolve into a short over time.

That kind of situation is a pain to debug.. the board will seem to operate normally for some amount of time, then it will die with no obvious change in the operating conditions. When you describe the operating conditions to someone who knows the hardware, they'll say, "it should never have worked at all."

danleeson wrote:Also, this just occurred to me (kind of off-topic), but is there a way to program the ESP8266 to use less power by trading off WIFI range?

Not that I know about, but the folks over at http://esp8266.com/ are the best source for information about that kind of thing.

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