Can FNIRSI DSO-152 Plus Test a DC Motor Controller Malaysia?

Can the FNIRSI DSO-152 Plus Mini Digital Oscilloscope be used to troubleshoot a DC motor controller?

For suitable low-voltage control signals, it can be useful for checking:

PWM presence

PWM frequency

Duty-cycle changes

Control pulses

Enable signals

Suitable feedback signals

However, a motor controller may also contain high-current switching circuits, MOSFETs, H-bridges and potentially hazardous voltage transients.

Therefore, it is important to distinguish between:

Low-voltage control-side testing

and

Power-stage testing

The DSO-152 Plus should not be treated as a universal instrument for probing every point inside a motor controller.

How Does a DC Motor Controller Work?

A basic motor-control system may include:

Controller or microcontroller

PWM output

Gate or motor driver

Power transistor or MOSFET

Motor power supply

DC motor

Depending on the design, it may also include:

Enable input

Direction control

Current sensing

Speed feedback

Protection circuitry

When the motor does not run, the fault can occur at any of these stages.

Why Is an Oscilloscope Useful?

A multimeter can tell you whether a voltage is present.

But a motor controller often uses signals that change rapidly over time.

For example:

PWM

A multimeter may show an average value.

An oscilloscope allows you to see the pulse waveform directly.

This can help answer:

Is PWM present?

Does duty cycle change?

Does the control signal reach the driver?

Start with the Symptom

Before probing the PCB, identify the actual problem.

For example:

Motor completely dead

Motor runs only at full speed

Motor speed cannot be adjusted

Motor starts and stops

Motor runs in only one direction

Motor jerks

Controller resets when motor starts

Different symptoms suggest different troubleshooting paths.

Step 1: Check the Motor Power Supply

Before looking for PWM, check whether the motor system has the required supply voltage.

Use an appropriate multimeter.

Check:

Input supply

Controller supply

Motor supply

Low-voltage logic rail

A motor cannot run correctly if the required power is missing.

Logic Supply and Motor Supply May Be Different

A motor controller may have:

5 V or 3.3 V logic

while the motor operates from:

12 V

24 V

or another supply.

Do not assume all parts of the board use the same voltage.

This distinction is important when choosing a test point.

Step 2: Check Whether the Controller Is Alive

If the board uses a microcontroller, look for basic signs of operation.

Depending on the design, this may include:

Status LED

Display

Control response

Suitable low-frequency output activity

If the controller itself is not operating, the motor stage may never receive a command.

Step 3: Find the PWM Control Signal

In many motor-control systems, a low-voltage PWM signal is generated by the controller.

This signal may go to:

Motor driver IC

Gate driver

Optocoupler

Buffer

Power stage

Identify the correct point using a circuit diagram, PCB tracing or component datasheet where possible.

Step 4: Check Whether PWM Is Present

Connect the oscilloscope to the appropriate low-voltage PWM signal.

If the controller is operating, you may observe a repetitive pulse waveform.

If the motor command is active but there is no PWM where it should exist, investigate the controller side.

Step 5: Change the Speed Command

If the motor controller has a speed adjustment, change the setting.

Observe the PWM waveform.

Depending on the design, you may see the:

Duty cycle change

while the frequency remains approximately similar.

For example:

Low command → Narrower HIGH pulse

High command → Wider HIGH pulse

The exact behaviour depends on the controller design.

PWM Is Present but Motor Does Not Run

This is a useful finding.

It suggests that the control system is generating at least part of the expected command.

Now investigate the next stages.

Possible areas include:

Enable signal

Motor driver

Driver supply

Power transistor

Motor supply

Motor itself

Protection circuit

Do not immediately replace the microcontroller.

Trace the PWM Signal

Suppose you find PWM at:

Microcontroller output

Now check whether the same control signal reaches the next appropriate stage.

For example:

MCU PWM

→ Resistor

→ Buffer

→ Driver input

If PWM exists before one stage but disappears after it, you have narrowed the fault location.

PWM at MCU but No PWM at Driver

Possible causes include:

Broken PCB track

Open resistor

Faulty buffer

Optocoupler problem

Connector problem

Driver input fault

Signal tracing is often more effective than replacing components randomly.

Driver Has PWM but Motor Still Does Not Run

Now check whether the driver has the required operating conditions.

Depending on the circuit, investigate:

Driver supply

Enable

Fault input

Protection condition

Direction command

At this stage, the diagnosis may move closer to the power section.

Extra caution is required.

What Is an Enable Signal?

Many motor controllers require an enable condition before the output stage operates.

The board may have:

PWM present

but

Enable inactive

In that case, the motor may remain off.

Therefore, PWM alone does not prove the complete motor-control system is functioning.

What About Direction Signals?

For reversible motors, the controller may use separate logic to determine direction.

Depending on the circuit, this may involve:

Direction pin

Two control inputs

H-bridge logic

If the motor operates only in one direction, compare the appropriate control signals when forward and reverse are selected.

Motor Runs Only at Full Speed

If the motor runs but speed cannot be controlled, check whether the PWM command actually changes.

For example:

Minimum setting = 90% duty cycle

Maximum setting = 90% duty cycle

If the control signal does not change, investigate the command or controller side.

If PWM changes correctly but motor speed does not, investigate downstream circuitry.

Motor Does Not Reach Full Speed

Possible causes include:

Low supply voltage

Power limitation

Motor problem

Mechanical load

Driver issue

PWM command not reaching expected duty cycle

Use both a multimeter and oscilloscope.

Do not diagnose the problem from PWM alone.

Motor Starts and Stops Intermittently

This can be caused by:

Power supply drop

Overcurrent protection

Thermal protection

Loose connector

Control signal interruption

Motor fault

Mechanical overload

An oscilloscope can help determine whether the control signal disappears at the same moment the motor stops.

Watch the Low-Voltage Supply

Suppose the controller resets whenever the motor starts.

Monitor the suitable low-voltage supply rail.

You may discover a brief:

Voltage drop

or

Noise event

when the motor starts.

A multimeter may not make a short disturbance as obvious.

Use Single Trigger for Startup Problems

If the fault occurs only at startup, Single Trigger may help capture a suitable one-time event.

For example:

Start button pressed

→ Motor attempts to start

→ Supply dips

→ Controller resets

Capturing this sequence can provide useful evidence.

Motor Runs but Controller Resets

Possible areas to investigate include:

Power supply stability

Grounding

Motor-generated interference

Decoupling

Wiring

Protection circuit

Power distribution

Do not automatically assume the software is faulty.

What About Motor Electrical Noise?

DC motors can generate electrical noise.

Brush-type motors in particular may produce disturbances during operation.

You may see noise on:

Power rails

Control lines

Sensor signals

However, the measurement setup itself can also introduce apparent noise.

Use appropriate probe technique before concluding that the circuit has a serious noise problem.

Why Probe Connection Matters

Long probe connections can make a waveform appear noisier.

When investigating fast switching or motor noise, measurement technique becomes increasingly important.

A poor probe setup can produce:

Ringing

Noise pickup

Unstable waveform

Do not diagnose a PCB from a poor measurement.

Can DSO-152 Plus Measure Motor Voltage Directly?

This question requires caution.

A motor may be driven by a switching power stage.

The waveform may include:

High current

Fast switching

Voltage transients

Floating nodes

H-bridge outputs

The DSO-152 Plus should not automatically be connected across arbitrary motor terminals or switching nodes.

Understand the circuit topology first.

Control Side vs Power Side

For an entry-level oscilloscope, the control side is often the more appropriate troubleshooting area.

Examples may include suitable:

Microcontroller PWM

Enable signal

Direction signal

Low-voltage feedback

The power side can require more specialised equipment and measurement techniques.

What Is an H-Bridge?

An H-bridge allows a DC motor to be driven in different directions.

It uses switching devices arranged to control the current through the motor.

H-bridge outputs may not behave like a simple signal referenced to circuit ground.

This makes casual probing risky and potentially misleading.

Do not assume that an ordinary ground-referenced measurement method is appropriate.

What About MOSFET Gate Signals?

MOSFET gate-drive analysis can be more demanding than basic PWM checking.

Important details may include:

Gate voltage

Rise time

Fall time

Dead time

Ringing

Switching frequency

Reference point

Detailed power-electronics analysis may require a higher-performance oscilloscope and suitable probes.

The DSO-152 Plus should not be positioned as a professional power-electronics analyser.

Can DSO-152 Plus Test a 12 V Motor Controller?

The fact that a motor controller is labelled 12 V does not automatically make every test point suitable.

Switching circuits can generate transients, and some nodes may have complex reference conditions.

Check the actual circuit before measuring.

Use the DSO-152 Plus primarily where the expected signal is known and within the instrument's appropriate capability.

Can It Test a 24 V Motor Controller?

The same rule applies.

Do not decide suitability based only on nominal supply voltage.

You must consider:

Actual test point

Maximum signal

Transient behaviour

Circuit reference

Switching topology

Probe rating

Can It Test an Arduino Motor Driver?

For suitable low-voltage control signals, yes.

For example, you may check:

Arduino PWM output

Enable

Direction

This can help determine whether the Arduino is sending the expected command to the motor driver.

Example: Arduino PWM Present but Motor Stopped

Suppose:

Arduino PWM = Good

Motor = Not running

Check:

Driver supply

Enable

Motor supply

Driver condition

Motor

The Arduino may be working correctly.

Can It Test a Fan Controller?

For suitable fan-control signals, the DSO-152 Plus may help check:

PWM command

Tachometer feedback

But do not confuse the two.

PWM normally controls speed.

Tachometer feedback reports rotational information.

Identify the correct signal before interpreting the waveform.

Can It Test a Robot Motor Controller?

For low-voltage logic signals within its capability, it may help with basic troubleshooting.

But robot motor systems can include:

High-current drivers

Battery power systems

Fast switching

Encoder signals

Multiple motors

Complex feedback

A more capable oscilloscope may be required for detailed diagnosis.

DSO-152 Plus Bandwidth Limitation

The DSO-152 Plus is an entry-level instrument in the approximately 200 kHz bandwidth class.

It can be useful for suitable lower-frequency PWM and control signals.

But it is not appropriate for accurate analysis of every motor-control waveform.

High-frequency switching and fast edges may require substantially more bandwidth.

PWM Frequency Is Not the Whole Story

A motor PWM signal might have a fundamental repetition frequency that appears relatively low.

However, the switching edges contain much faster components.

Therefore:

PWM frequency below 200 kHz

does not automatically mean:

A 200 kHz oscilloscope reproduces the switching waveform accurately.

This distinction is important.

For Basic PWM Checking vs Detailed Switching Analysis

If your question is:

“Is PWM present?”

or

“Does duty cycle change?”

the DSO-152 Plus may be useful on a suitable low-voltage signal.

If your question is:

“What is the exact MOSFET switching behaviour?”

you may need more advanced equipment.

DSO-152 Plus vs Multimeter for Motor Controller Repair

Use the multimeter to check:

Supply voltage

Continuity

Motor resistance where appropriate

Static DC conditions

Use the oscilloscope to check suitable:

PWM

Control pulses

Duty cycle

Feedback

Power rail behaviour over time

Using both provides a more complete picture.

Don't Replace the Motor Driver Too Quickly

If the motor does not run, the driver IC is not automatically defective.

Possible causes include:

No PWM

No enable

Missing driver supply

Protection active

Motor fault

Power supply problem

Controller fault

Connector problem

Measure first.

Replace components after the fault area has been narrowed down.

Compare with a Working Channel

Some boards control multiple identical motors.

If:

Motor Channel A works

and

Motor Channel B does not

compare the corresponding low-voltage signals.

For example:

PWM A vs PWM B

Enable A vs Enable B

Driver supply A vs B

This can provide a very useful reference.

Compare with a Working PCB

If you have an identical working controller, compare the same suitable test points.

Look for differences in:

PWM

Duty cycle

Enable

Control signals

Low-voltage power rails

This can speed up troubleshooting considerably.

Quick DC Motor Controller Troubleshooting Workflow

A practical sequence is:

1. Visual inspection

Check connectors, wiring and obvious damage.

2. Check power

Confirm controller, logic and motor supplies.

3. Check command

Does the speed control or command change?

4. Check PWM

Is the controller generating a suitable PWM signal?

5. Check duty cycle

Does it change when speed command changes?

6. Check enable and direction

Are the required control signals correct?

7. Trace PWM

Does the command reach the motor driver?

8. Check the load

Is the motor itself functional?

9. Investigate the power stage carefully

Use suitable equipment and measurement techniques.

This is much better than randomly replacing components.

When Is DSO-152 Plus a Good Choice?

The DSO-152 Plus can be useful when you mainly need to troubleshoot suitable:

Low-voltage PWM

Enable signals

Direction signals

Basic feedback pulses

Controller outputs

It is especially relevant to:

Students

DIY electronics

Arduino projects

Basic PCB repair

Low-frequency motor-control troubleshooting

When Do You Need a Better Oscilloscope?

Consider higher-performance equipment when working with:

Fast MOSFET switching

High-frequency motor drives

Detailed gate-drive analysis

Multiple signals simultaneously

High-voltage power stages

Industrial inverters

Advanced automotive motor control

Professional power electronics

The measurement instrument must match the circuit.

Safety Is Critical Around Motor Controllers

Motor-control systems can contain significant energy.

Do not assume:

“It is only a DC motor.”

The controller may include:

Large batteries

High current

Inductive transients

MOSFET switching

H-bridge outputs

High-voltage DC buses

Mains-connected power stages

Identify the circuit and measurement point before connecting an oscilloscope.

FNIRSI DSO-152 Plus for DC Motor Controller Testing Malaysia

The FNIRSI DSO-152 Plus can be useful for basic troubleshooting of suitable low-voltage motor-control signals.

A practical approach is:

Power

→ Command

→ PWM

→ Enable / Direction

→ Driver Input

→ Power Stage

→ Motor

For an entry-level oscilloscope, concentrate first on known, suitable low-voltage control signals rather than blindly probing the power stage.

MTM Precision supplies FNIRSI oscilloscopes and electronic test instruments in Malaysia.

If you are troubleshooting a motor controller, send us:

A photo of the controller PCB

Motor voltage

Controller model

Motor type

Description of the fault

Expected PWM frequency if known

Photo or video of your existing waveform

through WhatsApp.

We can help determine whether the FNIRSI DSO-152 Plus is suitable or whether you require a higher-performance oscilloscope or specialised measurement equipment.

MTM Precision Sdn Bhd

Showroom & Service Centre:
No. 29-1 & 2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.

Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my

Supplying FNIRSI and electronic test instruments throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.