# Simple probe PCDU

I am currantly working on an aerospace engineering project at my university which will fly on a sounding-rocket and I really suck at electical engineering, so I basically need a complete explanation of how this works:

I have a sort of small "space-probe", which has a built-in 3.7V LiPo-cell (500mAh) and I need 2 power-rails, which provide 3.3V at 50mA and 5V at (max) 750mA to the probes dual RP2040 flight computer assembly, the sensors which are connected to the computer via an I2C bus and 2 servos, which will not run simultaneously.

The only thing I came up with yet, is a resistive divider for the 3.7 to 3.3 part, which is pretty wasteful though and will drain the cell way too fast. Although there are a couple of explanations of how to build step-up and step-down converters, I've not found one yet, which is simple enough for me to understand and I don't just want to copy something I see and not get how it works. It does not need to be adjustable or anything. Just 3.7 to 3.3 and 5.0

• How would you generate a 5V supply from a 3.7V battery with a divider, given that negative value resistors are not easily available? Is there already a step-up regulator in the circuit? Also the individual current requirements of each rail make a big difference. It's sometimes quite reasonable to generate 5V at high current one way and use a much simpler way to generate a relatively tiny current at 3.3V. Commented Feb 26, 2023 at 19:45
• What is a "probe" in this context? Commented Feb 26, 2023 at 21:24
• @Caeleste In the context of electrical engineering, the word "probe" has a very different meaning; it refers to one of these or these. So your talking about a battery and a computer threw me off quite a bit! Commented Feb 26, 2023 at 21:37
• electronics.stackexchange.com/questions/106718/… Commented Feb 27, 2023 at 14:01
• What exactly is the 5V for? Perhaps whatever it is could be redesigned to make life easier. RP2040 itself doesn’t need 5V. If ADC is not used then 1.8V is all it needs, assuming the peripherals are OK with that. Commented Feb 27, 2023 at 21:37