MB102 Breadboard Power Supply 3.3V/5V

Overview

The MB102 is a breadboard-mounted power supply module that turns a wall adapter or USB cable into clean 3.3V and 5V rails for your prototype. It plugs straight onto the standard 830-point or 400-point breadboard's power rails — just push it down, flip the on/off switch, and you have regulated power without any soldering.

Each side (left and right rail of the breadboard) has its own jumper that lets you choose 5V, OFF, or 3.3V independently. So you can run your Arduino logic on one rail at 5V and your sensor on the other rail at 3.3V — both from the same module.

The module accepts 6.5-12V DC through the barrel jack or 5V via the USB port, then regulates it down using AMS1117-5.0 and AMS1117-3.3 linear regulators. With on-board filtering capacitors and a power LED, it's a reliable workhorse for any breadboard project.

At a Glance

DC Input

6.5V - 12V

USB Input

Outputs

3.3V or 5V

Output Current

700 mA max

Form Factor

Breadboard mount

Per-Rail Jumper

5V / OFF / 3.3V

Specifications

Parameter	Value
Regulators	AMS1117-5.0 + AMS1117-3.3 (linear)
DC Input Range	6.5V - 12V (5.5×2.1mm barrel jack, center positive)
USB Input	5V via USB-A connector
Output Voltages	3.3V and 5V (selectable per rail)
Maximum Output Current	700 mA per rail
Power LED	Green, on when switch is ON
On/Off Switch	Slide switch (master power)
Berg Header	5V, GND, 3.3V (4 pins)
Compatible Breadboards	830-point and 400-point standard breadboards
Dimensions	~52 × 35 mm

Pinout Diagram

Wiring Guide

Breadboard Setup

The MB102 is designed to mount directly onto the power rails at one end of a standard breadboard. The four pins on the bottom of the module slot into the + and − rails on both sides.

MB102 Output	Breadboard Rail
Left + (red)	Top + rail (left side)
Left −	Top − rail (left side)
Right + (red)	Bottom + rail (right side)
Right −	Bottom − rail (right side)

Tip: Some breadboards have split power rails — meaning the rail is broken into two halves in the middle. If your project draws power from both halves, add jumper wires to bridge the gap so both halves get power.

Power Sources

You can power the module in three ways. Pick the one that suits your bench.

Source	Connector	Notes
9V wall adapter	DC barrel (5.5×2.1mm, center positive)	Best for sustained current or when 5V USB is too weak
USB cable	USB-A port on module	Limited to 500 mA (USB 2.0) — fine for most projects
Berg header	5V or 3.3V pin (input)	Used to power the module from a known-clean rail

Warning: Don't power both DC and USB at the same time. The module doesn't have diode-OR protection, so reverse current flow can damage the regulator or the host computer's USB port.

Jumper Settings

Each rail (left and right) has a 3-position jumper that selects the output voltage independently. Move the jumper before powering on.

Jumper Position	Rail Output
5V	5V regulated
OFF	No output (rail floating)
3.3V	3.3V regulated

Tip: Run one rail at 5V and the other at 3.3V for projects that mix logic levels — for example, an Arduino Uno at 5V on one rail and an ESP32 or sensor at 3.3V on the other.

Code Examples

The MB102 is a passive power-supply module — it does not require any microcontroller code. Just set the output voltage with the rail jumper, flip the on/off switch, and connect VCC and GND of your project to the breadboard rails.

Example: Powering an Arduino Uno from a 9V Adapter

setup-instructions.txt

1. Plug a 9V wall adapter into the DC barrel jack.
2. Set both rail jumpers to "5V".
3. Flip the on/off switch to ON.
4. Verify the green power LED is lit.
5. Connect a wire from any "+" rail hole to the Arduino 5V pin.
6. Connect a wire from any "-" rail hole to Arduino GND.
7. The Arduino now runs from the MB102 instead of USB.

Frequently Asked Questions

Can I power both the 5V and 3.3V rails at the same time?

Yes. The two rails are independent — set the left jumper to 5V and the right to 3.3V (or vice versa) and you'll have both voltages available simultaneously. Each rail has its own regulator and 700 mA capacity.

What input voltage range works?

DC barrel jack: 6.5V to 12V. Below 6.5V the regulators can't maintain a clean 5V output. Above 12V the AMS1117 regulators get hot and may shut down on thermal protection. The USB input is fixed at 5V.

How much current can it deliver?

The AMS1117 is rated at 1A peak, 700 mA continuous per rail. With both rails active you can pull a total of around 1.4A — but at that point the regulator will get hot, especially with a 12V input. For sustained high current, attach a small heatsink or use a switching supply instead.

Is the output regulated and clean enough for sensors?

Yes for most analog and digital sensors. The AMS1117 has on-board filtering capacitors and produces a stable rail with low ripple (~30 mV typical). For very sensitive analog circuits (audio amplifiers, ADCs reading fine voltages), add an extra 10 µF + 0.1 µF capacitor pair near the load.

My module gets warm. Is that normal?

Yes, especially with high input voltage and high current draw. The AMS1117 is a linear regulator — it dissipates the difference between input and output voltage as heat. With 12V in and 5V out at 500 mA, that's 3.5W of heat. Reduce input voltage (use a 9V adapter instead of 12V) or attach a small heatsink.

Can I use this for motor projects?

For low-current motors (small servos, micro-DC motors under 200 mA), yes. For larger motors that can spike to 1-2A, use a dedicated motor power supply instead — motor inrush current can drop the rail voltage and reset your microcontroller. The MB102 is best for logic and sensor power.

What's the polarity of the DC barrel jack?

Center positive (the inner pin is positive). Most off-the-shelf 9V adapters are center positive. Check the label on your adapter — there's usually a polarity diagram. If you reverse polarity, the on-board protection diode shorts the input but may eventually fail.

Documentation