# Switching 12VDC >30A to 5VDC <0.1A

#### mitchnaake

Joined Nov 12, 2022
2
G'day,

I've recently started planning a self-made ECU project, and will need a way of powering a small microcontroller (Raspberry Pi Pico or ESP32) from a small motorcycle battery.

I want to know how I can set this up, and if there is a solution that will be compact enough to fit within a small enclosure of the ECU, or even be integrated into the PCB that I'm currently designing.

Many thanks,

Please don't be too harsh, I'm quite new to this stuff.

Mitch

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#### Dodgydave

Joined Jun 22, 2012
10,583
Ok so what voltage is the battery and what voltage do you need for the raspberry pi, any current requirements?

#### mitchnaake

Joined Nov 12, 2022
2
Ok so what voltage is the battery and what voltage do you need for the raspberry pi, any current requirements?
Here's the specs for both the battery and the microcontroller.

Battery:

Microcontroller [ESP32]:
- >=5VDC to <= 10VDC
- Consumes ~100mA to 200mA

#### DickCappels

Joined Aug 21, 2008
9,497
On second thought, we are only talking about 100 ma out, so as a practical matter you can just use a plain old 78M05 linear regulator without losing much, unless efficiency is at the top of your list of requirements.

#### Dodgydave

Joined Jun 22, 2012
10,583

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#### MisterBill2

Joined Jan 23, 2018
13,680
If you choose to use a linear regulator, which will be the smallest and simplest way, but not the most efficient way, be sure to add the two recommended capacitors. Those are 0.1 microfarad rated at least 10 volts. They need to be connected quite close to the regulator.
As part of your "quite new stuff" education, you should be able to find in line the application notes for the 78M05 regulator for an explanation about why this is important AND you will see what is meant by "close."
And Welcome to the AAC forum realm.

#### DickCappels

Joined Aug 21, 2008
9,497
In addition to @MisterBill2 's notable advice, be sure to check the data sheet from the manufacturer of the particular regulator you choose, if you chose to go the LM7805 route. Recommendations for bypassing vary slightly by manufacturer.

#### bertus

Joined Apr 5, 2008
22,118
Hello,

If you still would go for a switching regulator, have a look at these RECOM ones.
The 78E series ( Low profile (L*W*H=11.6*8.5*10.4mm)) is smaller than the 78B series ( Low profile (L/W/H=11.5 x 8.5 x 17.5mm))

Bertus

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#### Tonyr1084

Joined Sep 24, 2015
7,185
Others have it covered. Since you're "New" to electronics, here's a few things that sometimes people don't understand. If I'm covering something you already know - don't think I'm looking down on you. Just covering one base you might not fully understand.

Your battery is capable of producing 100 CCA (Cold Cranking Amps). For a motor cycle that's probably more than enough for a small battery to turn the engine over. A battery may be capable of many amps but the electronics hooked to it may only draw a few amps. Or even a few milli-amps. Just because the battery has a high capacity doesn't mean your electronics has to deal with all that power. It's just there for when needed.

Ron