CPX Current Draw and USB Battery Pack

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stevensrmiller
 
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Joined: Wed Jul 20, 2022 10:14 am

CPX Current Draw and USB Battery Pack

Post by stevensrmiller »

Hi all! First time posting here. I looked for existing answers on this, but didn't find one.

I'd like to use a USB battery pack to run my CPX. Adafruit sells the PKCELL 2200 mAh pack, which looks ideal. However, their description points out that, "If using it with a low current load, say under 100mA, the pack may 'fall asleep.'" Perhaps this is because the pack is designed to be a portable charger for your iPhone or similar device, and it uses this current level to determine when the device is fully charged.

So I am wondering if the CPX consistently draws enough current to keep this pack "awake." Is it more than 100 mA? I thought it would be easy to find a spec on this, but I haven't had any luck.

Thanks for any answers or guidance.

Stevens

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mikeysklar
 
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Re: CPX Current Draw and USB Battery Pack

Post by mikeysklar »

Your CPX will likely draw around 15mA in an idle mode, but significantly more when LEDs or the SAMD21 M0 processor are being utilized.

It might make sense to consider a JST connected LiPo battery pack (instead of using the USB port).

https://www.adafruit.com/?q=jst+lithium ... =BestMatch

Should you want to measure the load specific to your application that can easily be done with a USB current monitor.

https://www.adafruit.com/product/2690

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stevensrmiller
 
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Re: CPX Current Draw and USB Battery Pack

Post by stevensrmiller »

mikeysklar wrote:Your CPX will likely draw around 15mA in an idle mode, but significantly more when LEDs or the SAMD21 M0 processor are being utilized.
Thanks, that's great info! I could probably "fake" a bigger draw by just leaving some LEDs on, or even just put a 50-ohm resistor in parallel with it. Even wasting 100 mA, a 2600 mAh battery would last several hours.
It might make sense to consider a JST connected LiPo battery pack (instead of using the USB port).
I have one, but that's why I'm looking for a USB alternative. Constantly connecting/disconnecting the USB jack feels like it puts a lot of strain on the CPX's USB connector. It's also difficult, whereas plugging/unplugging the USB-A jack at the computer end is quite easy.
Should you want to measure the load specific to your application that can easily be done with a USB current monitor.
Great tip, thanks again.

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