Boost Converter - Where to draw power from?

Hardware
1

Hi!!
Quick question for everyone. I’m needing 5V from a Boron to power some sensors. I’ve got the boost converter from Pololu linked below. To keep load off of the 3V regulator I’d like to connect the boost converter to the battery through the LiPo pin. My question is will having the boost converter on the LiPo pin interfere with the charging or SOC reporting capabilities of the Boron? Long term will this cause any damage to the charging circuitry or are there any gotchas I should aware of? I plan to disable the boost converter if in a situation where I need to conserve battery power.

If it’s important I’ll also be charging the Boron with a 6V solar panel through the Vusb pin. Total load will be about 200mA at 5V.

thanks for the help!!

2

@mdavey ,

I have a very similar setup. I have Borons which I power with a 6V 3.5W panel. I need 5V for some soil moisture sensors and so I have built a little 3.3V to 5V boost converter board with an “enable” feature to turn it on and off. I power this converter from the 3.3V regulator as it has a 1000mA capacity which I am not coming close to taxing.

You could power the converter from the Li+ pin but I like the fact that I can use the Boron’s Enable pin to power down the device, the cellular modem and my peripherals.

Hope this helps,

Chip

3

@chipmc ,

I appreciate the insight. A while ago I tried a charge pump type boost converter and powered it from the 3V regulator. At the time I was using a TMP36 temperature sensor to keep track of the enclosure’s internal temperature for battery protection. The temp sensor was powered at 3V but adding the boost converter for the other sensors absolutely wrecked my readings for temperature. I’ve since gone through several iterations and changed temp sensors but was hoping to avoid any more pitfalls. Also didn’t want to damage the boron as they are hard to come by these days.

I’ll try using both the LiPo pin and the regulated output and see what works best.

thanks!

4

@mdavey ,

Makes sense and good luck with your project. One point you reminded me of is that you can set the order of operations to reduce issues from power fluctuations. For example, here is my order of operations:

  • sleep
  • wake and take battery state of charge and temperature measurements (TMP36 like you)
  • enable the 5V boost converter and wait 100mSec
  • take soil moisture measurements
  • disable the boost converter
  • publish readings to the queue
  • Power on the cellular modem and connect to Particle
  • clear the publish queue
  • disconnect from Particle and power down the cellular modem
  • repeat

By doing things in this order, my hope is to minimize

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