here is what I would like to do. I would like to include a RPi in a Canon BG-E7. Since the grip supply a 7.2V, 1800mAh and the RPi run at 5V, would Pololu Adjustable Boost Regulator 2.5-9.5V would be the best solution to start with? Also, since I need to provide an input voltage lower than 5V to the regulator, what would be your recommandation to drop the 7.2V, output by the BG. Is a Zener would be a good idea to keep the maximum possible current available? Note that I will transmit photos either over wifi or bluetooth, not sure for now. Is that solution will be noisy or could affect transmission? Any other ideas with better results would be greatly appreciated.
A boost regulator outputs higher voltage than it inputs. When the input is 7.2V and the output should be 5.0V, you need a buck (step-down) regulator. When the difference in input voltage is small, you may need a two-way (boost/buck, or SEPIC) regulator, because there is a minimum input voltage for a given buck regulator to generate its set value. 7.2V is enough for most buck regulators to generate steady 5.0V.
No Zener diode is necessary; the Raspberry Pi will draw as little or as much current as it demands from the source. Current is not “pushed” from the Canon.
The Raspberry Pi can be powered from pins 2 and 6 – provide +5V to pin 2, and GND to pin 6. I do this for a project of mine.
Thanks jwatte for this quick response. Among the parts offered at Pololu, do you have any specific recomandation? I believe I should be attentive about power supplied, working temperature and size because I ought include it inside the BG. Do you think that the S7V7F5 would be a good choice? Also, do you think that the working temperature of the voltage regulator could cause temperature issues inside the BG?
I know nothing about the heat handling of the BG-E7, nor if there’s even enough space inside that battery grip to mount the stuff you want.
From the specifications, the S7V7F5 seems like it should work, assuming you’re not drawing too much additional current from the Pi (the Pi itself wants between 500 and 800 mA.)
