HELP REQUEST - Adafruit Feather 32 and MPU6050 and Power issues.

[JumperD1981]

This is...was suppose to be simple project...but it has escalated into quite the beast.

In short I am trying to build a device that can sense when it moves too much from whatever it is calibrated at...which we have working...and this device will relay to a small number of other devices used as a sort of repeater to deliver a alert to an app. All that is working...but we are having issues charging. Let me elaborate.

Someone suggested I use a ball bearing switch to keep the charging port disabled while outdoors, to prevent a short. This works to a point. When I turn it upside down it does indeed allow that port to become active and allows charging but it also turns on the device bypassing the power button...which of course causes the alarm to go nuts. Plus the added draw of the MPU, Buck to Piezo, and Feather makes the charge take forever...

What I would like to do is keep the charge port inactive(no voltage) until voltage is applied and when it is applied the MC(feather 32 by adafruit) is turned off. I believe turning off everything via pulling to ground the EN pin will work...but how do I keep voltage off the charge port when not connected?


In short, any ideas on how to keep disabled the charge port when no voltage is present, then disabled everything when voltage is?

 

[Nigel Goodwin]

Post the schematic, otherwise we're just guessing - but simple diode gates may well do what you need. I use this for charging a device we build and sell - the device is normally switched OFF (by a processor activated transistor switch), and this is connected via a diode to the input of a 5V regulator. A diode also feeds the same point from the charging feed, plus a pair of resistors feed an I/O pin on the regulator (from before the diode) - so if this is high it's charging. As the device boots up, it checks the I/O and selects if it's in charging mode or not.

 

[JumperD1981]

I am not terribly familiar with design, but rather assembly of circuits...but I think, based on what I have read, that I can use a 2N3904 transistor as a switch.

One Transistor will have it's base sense voltage on the charge port and enable the EN pin to go to ground, and the other Transistor will sense this same voltage and enable the charge circuit. This will enable to both disable all electronics during charging, and disable the port when no voltage is present.

Does that sound about right?

 

[Nigel Goodwin]

I am not terribly familiar with design, but rather assembly of circuits...but I think, based on what I have read, that I can use a 2N3904 transistor as a switch.

One Transistor will have it's base sense voltage on the charge port and enable the EN pin to go to ground, and the other Transistor will sense this same voltage and enable the charge circuit. This will enable to both disable all electronics during charging, and disable the port when no voltage is present.

Does that sound about right?

Post a schematic.

 

[JumperD1981]

I will attempt to make a schematic when I get a chance...right now they are hand drawn sketches more than anything...

 

[JumperD1981]

Please understand that I can draw out something understandable faster than using a program like Eagle to make an actual legit schematic. A person on a forum other than this one already suggested that I get rid of the switch on the battery and move it to the EN pin which will eliminate part of my issue. I think that will work nicely. Now I need to figure out why I have 2.8Volts on my Charge port that goes to the USB port on the MC...and figure out how to disable that...perhaps with a 2N3904?

 

[JumperD1981]

Okay, so 1st major issue has been resolved. Using switch for enable EN pin instead of the battery positive fixed the odd issue of it turning on when charging.

Now my last question.
Is it going to be possible for me to completely stop flow of voltage out the DC charge port when not plugged in? In other words I want something to stop the voltage before it reaches the charge port. I tried a transistor as previously mentioned which actually worked perfectly to stop that voltage I mentioned, but it also created some heat, and would likely not last long, also when charging over 1.8 volts was missing from the output...meaning there was not enough to charge properly. Now I am thinking a Diode of some sort. This device uses a standard 2.1 Amp/5V charger, and I am using a IN5819 which sort of works...it is letting more of the voltage through when charging but the charging port still has about 2V on it. should I double them up?