powerboost 500+ connect LED to warn of low power?

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maybecoding
 
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powerboost 500+ connect LED to warn of low power?

Post by maybecoding »

Hi, I am wiring a Powerboost 500+ with a 3600mAh LiPo battery, to power a LCD screen and a RPI zero 2W.

I mounted a switch so I can turn off the whole setup with one switch, but I would like to put this inside an enclosure, and if I do so I won't be able to see the low battery RED LED.

Looking at the pinout of the PB500+ I see that there is a pin called LBO that is connected to the LED on board; can I connect a resistor and a LED to this pin and to GND on the board, so I can install that on my enclosure? If so, what should the resistor capacity? Thanks

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dastels
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by dastels »

Looking at the schematic it doesn't look like LBO can drive a LED directly. You could replicate the circuit used for the onboard LBO LED: https://learn.adafruit.com/assets/17555.

Dave

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maybecoding
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by maybecoding »

Thanks! So a 1K resistor and a LED should do, right?

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dastels
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by dastels »

No. That would be driving the LED directly. I was think more of replicating the driver transistor circuit. The datasheet says that LBO is rated for 100uA when it's low which explains the driver circuit since an LED typically wants ~20mA. You can get the transistor from mouser (and probably digikey as well): https://www.mouser.com/ProductDetail/on ... 52BQ%3D%3D.

Dave

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maybecoding
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by maybecoding »

Oh, I see what you mean; I missed the transistor there on the circuit.

Is that the only way to get the LED to shine or can I take the signal directly from another place on the board?

Also is the recharge rate fixed? I noticed that my current measure about .3A when recharging the battery, no matter if I am using a 20W charger or a 60W charger. I guess it is set to use 250mA to not overload a computer USB port? Would be awesome if the charging rate could be changed, like on the other LiPo chargers you sell (I have another one that just charge and there was a pad to solder to get 500mA or leave it disconnected to use 250mA)

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dastels
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by dastels »

No. That's how you'll have to do it. There is no other signal to use. I suppose you could replace the on board LED with an external one, but that'd be some tricky hacking.

The charge current is completely independent of the power supply. Power rating on a power supply/charger is how much power it can provide. That isn't an amount of power that gets pushed into a circuit. The charge current is stated to be 500mA. It actually says that on the bottom of the board. But yes, the charge current is fixed on these boards.

Dave

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maybecoding
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by maybecoding »

Thanks Dave, will go ahead and set up the circuit as suggested. The LED on the board is so small that it is quite impossible for me to be able to re-wire it :)

BTW is there a way for me to get the battery level somehow while running Linux? Assuming I can get the low voltage using the GPIO on the RPI, but is there something communicated by the board about the battery level?

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dastels
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by dastels »

Nothing on the PowerBoost other than LBO. However you can use https://www.adafruit.com/product/4712 to monitor the battery level. The best thing about that is that it takes into account the discharge curve to give you a % full reading. Just connect it between the battery and the powerboost.

Dave

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maybecoding
 
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Re: powerboost 500+ connect LED to warn of low power?

Post by maybecoding »

Thanks, so that would only tell me when the battery is low, but nothing else.

The board you posted is exactly what I was looking for; much appreciated!

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