Switching between standalone and rPi.


Phi Dang

New member
I've been on the site lurking for a couple of days now and I'm about to order components to build rPi version. I love the relative low cost of this unit and customizability.

Since I do a bit of camping during the summer, I want this to also function as a standalone meter for lower power consumption. Can I just simply populate IC4 when building the rPi version and then power either the rPi or heatermeter depending on the functionality that I want?

Additionally is anyone running these units purely off battery packs? What kind of sizing would be needed for a 12 hour burn for either standalone or rPi?

Thanks for the help!
Sure, the 12v connects directly to the HM4 board so attach the RPI if you want the web access and logging or run it without for basic PID functions. I have run the older linksys heatermeter off D batteries to control a blower on a UDS for about 6 hours and it worked fine.

Wanted to add one more thought, if you don't have a RPi for the initial setup, you'll need to install a bootloader on the AVR and upload the heatermeter code via FTDI. If you have the RPi for initial setup all this is done automagically.
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Bryan Mayland

TVWBB Hall of Fame
RJ nailed it, but to add some more data, the HeaterMeter board pulls about 10mA. It will run off a 3.3Ah 12V battery taken out of a UPS for at least a week. The fan pulls about 150mA though so it will drain the battery in about 20 hours if running full speed. Depending on the fan usage you'll get somewhere between 20 hours and a week on a charge. That's actually a fairly small battery (3lbs) too.

You can populate IC4 always. I always have mine in. Technically you're not supposed to do that but it seems to work ok.

Phi Dang

New member
Thanks for the reply guys and I they've answered my questions. I definitely wanted to get a rPi from the start so I can avoid the additional cost of a flasher.

Hopefully I'll be reporting in about my sucess next week!