Fixing Missing Routed Traces

0:44

Running design review.

Analyzing the schematic.

Analyzing the PCB layout.

Identifying unrouted nets.

Identifying unrouted nets around U1.

I inspected the local schematic and PCB data around U1. For this kind of debug, the right source order is to use schematic, review, and layout inspection together .

What I can tell so far

The DRC confirms there are still 53 airwire errors globally, and U1 is involved in the PCB because its footprint appears in layout and one of the reported problem pads matches the same footprint family seen around it.

The review output does not expose a clean net -> offending pad mapping, so I can’t name the exact DRC airwire by net from the review alone. But I can identify the U1-connected nets that still need routing attention first.

U1 nets to inspect first Highest priority: direct off-board / header connections

These are the easiest to miss in layout and most likely to remain as visible airwires from U1:

Table

U1 pin	Net	Other endpoint
D2	`Net (U1 - D2)`	J5 pin 4
D3	`Net (U1 - D3)`	J5 pin 5
D4	`Net (D4 - P1)`	J5 pin 3
D5	`Net (D5 - P1)`	J8 pin 3
D6	`Net (D6 - P1)`	J7 pin 3
D0/RX	`Net (U1 - D0/RX)`	J6 pin 5
D1/TX	`Net (U1 - D1/TX)`	J6 pin 4
A4	`Net (12C - Pin_3)`	12C pin 3
A5	`Net (A5 - P1)`	12C pin 4
A6	`Net (A6 - P1)`	J9 pin 3
A7	`Net (A7 - P1)`	J10 pin 3
D12/MISO	`Net (U1 - D12/MISO)`	EN pin 1

Next priority: control nets to motor drivers

These also originate at U1 and are common airwire candidates if routing was only partially completed:

Table

U1 pin	Net	Other endpoint
D7	`Net (D7 - P1)`	U2 IN1
D8	`Net (D8 - P1)`	U2 IN2
D9	`Net (U2 - ENB)`	U2 ENA / ENB
D10	`Net (U1 - D10)`	U2 IN3
D11/MOSI	`Net (U1 - D11/MOSI)`	U2 IN4
A0	`Net (A0 - P1)`	A4988 DIR
A2	`Net (U1 - A2)`	A4988 DIR
A1	`Net (A1 - P1)`	R1 and A4988 STEP
A3	`Net (A3 - P1)`	R2 and A4988 STEP

Nets around U1 that are probably already partly covered

These are power nets, so they may already be connected by broader routing or fills, but still deserve checking:

Table

U1 pin	Net	Notes
+5V	`VDD`	Shared with 7805, U2, headers
VIN	`Net (+9V - P1)`	Shared with 7809, C2, power-select headers
GND	`GND`	Shared with many parts; usually less likely if plane/fill exists, but still possible on a 2-layer board

Important schematic issue I noticed

There is a likely logic conflict in the schematic:

U1 A0 goes to DIR on A4988
U1 A2 also goes to DIR on [A4988::8d62cfa4)

And similarly:

U1 A1 goes to STEP
U1 A3 also goes to STEP

That is not an airwire problem by itself, but it is suspicious and worth verifying before you spend time routing those nets.

Best next check in the editor

In PCB view:

Turn on Airwires
Click U1
Start by tracing these pins visually: D2, D3, D4, D5, D6, D0/RX, D1/TX, A4, A5, A6, A7
Then inspect D7 to D11, A0 to A3

If you want, I can do the next pass and narrow this further to a shortest “route these first” list based on which U1 nets are most likely still unrouted near the motor-driver area versus the header area.

Prioritize shortest list

Check motor-driver nets

Flag logic conflict

33 days

why are two 7805 voltage regulators connected in parallel, knowing both give a 5...

dinosan

@copilot why are two 7805 voltage regulators connected in parallel, knowing both give a 5V output?

copilot

Using two

7805

voltage regulators in parallel is generally not recommended due to potential issues with load sharing and stability. However, in some cases, people might attempt this to increase the total current available to the circuit.

Here are potential reasons and considerations for this configuration:

Increased Current Output: The idea might be to enhance the current capacity by using two regulators if the load current exceeds the capability of a single $7805$ . Each $7805$ is typically capable of providing up to $1A$ of current.
Load Sharing Issues: Without proper measures, the regulators will not automatically share the current equally because small differences in their output voltage set points will cause one to supply more current than the other. This can lead to overheating and reduced life expectancy of the overburdened regulator.
Stability Concerns: The interaction between the two regulators might lead to oscillations or stability issues without additional circuitry ensuring proper load sharing.
Dropout Voltage: Ensure the input voltage is sufficiently above the dropout voltage for each regulator for them to maintain a stable $5V$ output.

To implement a better design, consider using a higher current regulator or designing a proper load sharing circuit. If heat dissipation and current requirements are of concern, other solutions like switching regulators might offer better efficiency and heat management.

VCC

MOT2

MOT1

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Project Name

Arduino Multipurpose PCB hLQ8

Description

This is the multipurpose PCB that works with Arduino Nano, a way that you can run 2 Stepper motors, 2 DC motors, 2 Servo motors at the same time and this is not it you can even connect BT module, rotary encoder, I2C device, potentiometer at same time. This PCB is very much helpful in building any project and no need to worry about messy wire connections.

Properties

License

creativecommons.org/licenses/by/4.0/

Pricing & Availability

Distributor	Qty 1
Arrow	$21.31–$21.47
Digi-Key	$7.57–$47.53
LCSC	$0.49–$1.07
Mouser	$7.91
Verical	$59.08–$59.33

Controls

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dinosan / Arduino Multipurpose PCB hLQ8

Schematic