AWS IoT Jobs, Azure Device Update, and Blynk.Air all provide OTA management dashboards with staged rollout, version tracking, and fleet health monitoring. If you are already using these platforms, their OTA integration is often better than building your own system.

Always verify firmware signatures before applying an OTA update. An HTTPS connection protects against network interception, but not against a compromised update server. Firmware signing and secure boot are the real defense against a fully compromised update infrastructure. ESP-IDF supports RSA 3072 and ECDSA 256 for this purpose.

Partition Table for OTA, Don't Wing It

A common mistake is starting with the default partition table, then realizing later that the OTA partitions are too small for your growing firmware. Plan partition sizes before shipping. A good rule of thumb is that each OTA partition should be at least 1.5 times your current firmware size, to allow room for future features.

Quick check: In ESP-IDF, run idf.py size-components to see exactly how much flash each part of your firmware uses. Identify the large consumers early and optimize when needed.

The day you ship a product without OTA updates is the day you commit to never fixing bugs or adding features without physically retrieving every device. That's fine for a breadboard. It's a business problem at any scale. Here's how OTA works on ESP, from the simplest version to what production systems need.

How OTA Works Under the Hood

The ESP's flash is divided into partitions defined by a CSV file. For OTA, you need at least two app partitions: ota_0 and ota_1. Your current running firmware resides in one of them. During an OTA update, the new firmware writes to the other, the inactive one. When writing is complete and the SHA256 hash verifies, the bootloader checks it on reboot, and the device restarts into the new firmware.**

If the new firmware fails to boot correctly, for example if it crashes repeatedly or never calls esp_ota_mark_app_valid_cancel_rollback(), the bootloader automatically marks the update as invalid and reverts to the previous working firmware on the next power cycle. This rollback mechanism prevents bricks and is a critical production safety net.

Three OTA Methods, Pick Your Level

ArduinoOTA, for development

Install the library, add four lines to setup(), and your board appears in the Arduino IDE port list over the network. Upload new firmware exactly like USB over Wi-Fi. No authentication by default, so add a password at minimum. Not for production, but for rapid development iteration it is extremely convenient.

HTTP OTA, the production standard

Your device polls an HTTPS endpoint every N hours, or on command from the server. The endpoint returns either a 304 Not Modified response, meaning nothing to update, or a new firmware binary. The device downloads it to the inactive partition, verifies integrity, optionally checks signature, then reboots. ESP-IDF's esp_https_ota() handles most of this in a few lines of code.

ESP Sleep Modes: The Practical Guide to Not Killing Your Battery

In the previous post, we covered the five power states of the ESP32 family and took a deep dive into deep sleep, the go-to mode for battery-powered sensor nodes. Now we turn to light sleep, a mode that offers sub-milliampere current consumption while preserving RAM state and enabling fast wake-up.

Light Sleep: The Overlooked Middle Ground

Light sleep pauses the CPU while keeping RAM powered, typically around ~0.8 mA depending on configuration. When a wake source fires, execution resumes exactly where it stopped, no reboot, no re-initialization required. If your device needs to respond quickly to GPIO events but does not need to stay fully active all the time, light sleep is often the right choice.

The tradeoff is power. While ~0.8 mA is significantly lower than active mode, it is still much higher than deep sleep (~10 µA). At scale, this difference has a major impact on battery lifetime.

For devices that wake frequently, light sleep can be more energy-efficient overall because it avoids the repeated cost of system reboots and Wi-Fi reconnections. However, for longer sleep intervals measured in minutes or hours, deep sleep remains the clear winner.

Wake sources for light sleep include timers, GPIO interrupts, UART activity, and capacitive touch sensors. These are configured similarly to deep sleep using APIs such as esp_sleep_enable_timer_wakeup() and esp_sleep_enable_gpio_wakeup().

For a device that wakes up periodically to send data and then sleeps, which covers most of the battery IoT nodes, deep sleep is what you want. You call esp_deep_sleep_start() and the chip powers down to approximately 10 µA, keeping only the RTC oscillator ticking. Your specified wakeup source brings the chip back.

The GPIO16 trick for ESP8266: On the original ESP8266, you must wire GPIO16 to RST to wake from deep sleep via timer. The RTC fires a low pulse on GPIO16 which resets the chip. Forget this wire and your device sleeps forever.

On the ESP32, the timer wakeup is cleaner, no external wire needed. Call esp_sleep_enable_timer_wakeup(duration_in_microseconds) before esp_deep_sleep_start() and you're done.

Surviving Deep Sleep: RTC Memory

 Here's the subtle part: deep sleep kills your chip's state. All RAM is wiped. Your variables are gone. To preserve data across sleep cycles, use RTC memory, a small (16 KB) memory region powered by the RTC that survives deep sleep.

In Arduino: RTC_DATA_ATTR int bootCount = 0; that RTC_DATA_ATTR prefix stores the variable in RTC SLOW memory. Use it for boot counters, cached Wi-Fi credentials, last sensor value, or anything you need to remember between wakes.

 Cache your Wi-Fi BSSID and channel in RTC\_DATA\_ATTR variables. On subsequent wakes, pass them to WiFi.begin() explicitly to skip the channel scan. This alone cuts reconnect time from 3–5 seconds to under 1 second, a significant battery saving at scale.

ESP Sleep Modes: The Practical Guide to Not Killing Your Battery

Here's something that surprises new IoT developers: a device that runs 24/7 isn't always better than one that sleeps most of the time. For battery-powered sensors, aggressive use of sleep modes is what separates a device that lasts a week from one that lasts two years. Let's talk about how ESP sleep modes work.

The Five Modes, Explained Simply

The ESP32 family has five power states. Most tutorials only mention deep sleep, but understanding all of them lets you pick the right tool for each job.

Mode	Current	CPU Running?	Wi-Fi Active?	Wake Sources
Active (Wi-Fi TX)	~240 mA peak	Yes	Yes	—
Active (CPU only)	~20–80 mA	Yes	Off	—
Modem Sleep	~20 mA	Yes	DTIM sync only	Automatic
Light Sleep	~0.8 mA	Paused	Suspended	Timer, GPIO, UART, touch
Deep Sleep	~10 µA	Off	Off	Timer, EXT0/1, touch, ULP

Note: Current values are typical for ESP32 modules with LDO regulators. Actual consumption depends on module variant, operating voltage, and temperature. Deep sleep current on bare ESP32 chip can be as low as 5 µA; module-level consumption includes LDO quiescent current.

Relays are widely used in automation systems to control electrical loads such as motors, lamps, and industrial equipment. Two common types are mechanical relays and solid state relays (SSR). While both serve the same purpose, their working principles and performance characteristics are significantly different.

This article compares both relay types to help engineers choose the right solution for their application.

Working Principle

Mechanical Relay

A mechanical relay uses an electromagnetic coil to physically switch contacts.

Key characteristics:

• Uses moving parts
• Provides electrical isolation
• Produces clicking sound during operation

Solid State Relay (SSR)

An SSR uses semiconductor components (triac, MOSFET, or optocoupler) to switch loads without moving parts.

Key characteristics:

• No mechanical movement
• Silent operation
• Faster switching

Performance Comparison

Feature	Mechanical Relay	SSR
Switching Speed	Slow (ms)	Fast (µs)
Lifespan	Limited (wear)	Very long
Noise	Audible click	Silent
Heat Generation	Low	Higher
Power Consumption	Coil required	Low control power
Isolation	High	High (optical)

Load Handling

Mechanical Relay

• Suitable for AC and DC loads
• Handles high current surge
• Better for inductive loads

SSR

• Ideal for frequent switching
• Best for resistive loads
• Some types limited to AC only (triac-based)

Advantages and Limitations

Mechanical Relay Advantages

• Low cost
• Handles high current
• Good isolation

Mechanical Relay Limitations

• Contact wear over time
• Slower switching
• Mechanical noise

SSR Advantages

• Long lifespan
• Fast switching
• No mechanical noise

SSR Limitations

• Heat dissipation required
• Higher cost
• Leakage current (important for low-load systems)

Engineering Considerations

Choose based on application:

• Use mechanical relay for:
  • Motor control
  • High current switching
  • Low-frequency operation
• Use SSR for:
  • High-speed switching
  • Silent operation
  • Long-term reliability

Thermal management is critical when using SSR, especially in high-current applications.

Both mechanical relays and SSRs are essential components in automation systems. Mechanical relays are robust and cost-effective for general-purpose switching, while SSRs provide faster, quieter, and more reliable operation for high-frequency switching applications.

Selecting the right relay depends on load type, switching frequency, and system requirements.

#Automation#
#Relay#
#SSR#
#EmbeddedSystem#
#PowerElectronics#
#ControlSystem#

There’s often a goal in design to make something fully manufacturable—clear, predictable, and repeatable.

But in sheet metal, “perfect manufacturability” is rarely a fixed state.

Because even with well-defined processes, there are always variables:

• Material behavior differences
• Tooling conditions
• Sequence effects
• Assembly handling

So the question becomes less about eliminating variation, and more about designing in a way that remains stable under it.

Maybe manufacturability is not about perfection, but about resilience.

💬 Where do you personally draw the line between precision and robustness in your designs?

#sheet metal# #design guide#

We had a case where two batches of the same sheet metal part were produced using identical drawings and material.

On paper, they were the same.

But during assembly, slight differences were noticeable. One batch fit smoothly, while the other required minor adjustment during installation.

After investigation, there wasn’t a single root cause. Instead, it was a combination of small variations:

• Slight bend angle deviation within tolerance range
• Minor differences in coating thickness
• Tool wear between production runs

Each factor alone was acceptable. Together, they created a visible difference in assembly behavior.

It highlighted how manufacturability is often about managing variation, not eliminating it.

💬 How do you usually handle variation when everything is still technically “within tolerance”?

#sheet metal# #design guide# #tolerance#

At the beginning, a good sheet metal design meant something that was fully defined in CAD—no missing dimensions, no ambiguity, fully constrained geometry.

Over time, that definition shifted.

Now, a “good design” feels more like one that:

• Can tolerate small real-world variation
• Assembles without force or adjustment
• Doesn’t depend on perfect execution in every step
• Leaves controlled freedom where needed

The CAD model didn’t become simpler, but the expectations behind it changed.

It became less about controlling every detail, and more about ensuring the design still works when reality introduces variation.

💬 Has your definition of a “good design” changed over time as well?

#sheet metal# #design guide# #enclosure#

Across different sheet metal projects, there’s a pattern that becomes noticeable over time.

Designs that are easy to manufacture usually don’t try to control everything equally.

Instead, they tend to:

• Focus precision only on functional interfaces
• Allow flexibility in non-critical geometry
• Reduce dependency on exact bend positioning
• Avoid unnecessary feature density

Interestingly, these designs don’t look “less engineered.” They just distribute precision more intentionally.

On the other hand, designs that try to enforce uniform precision everywhere often require more adjustments during production.

💬 Have you noticed this difference between “fully controlled” designs and “selectively controlled” ones?

#sheet metal# #design guide#

The design itself was straightforward—a small sheet metal enclosure with multiple bends, standard material, and no unusual features.

On CAD review, everything checked out. Dimensions were consistent, tolerances were defined, and the geometry looked clean.

But during the first production run, small issues started showing up.

Some bends didn’t return exactly as expected, which slightly shifted alignment at the assembly stage. Nothing was completely out of tolerance, but the accumulated effect made the fit feel less smooth than intended.

What stood out most was that there wasn’t a single “error” to fix. It was more about how several small variations interacted together.

After reviewing it again, the focus shifted away from individual dimensions and more toward how the part behaves as a system.

💬 Has anyone experienced a design that passed review but behaved differently once manufactured?

#sheet metal# #design guide# #enclosure#

Current Transformer (CT) sensors are widely used for measuring AC current in industrial and embedded systems. They provide electrical isolation and allow high current measurement without direct electrical contact with the conductor.

This guide explains how to properly use CT sensors with microcontrollers for accurate current measurement.

How CT Sensors Work

A CT sensor operates based on electromagnetic induction. When AC current flows through the primary conductor, it induces a proportional current in the secondary coil.

Key points:

• Output is current (not voltage)
• Requires burden resistor to convert to voltage
• Only works with AC signals

Basic Connection to Microcontroller

A CT sensor cannot be connected directly to an ADC input. The output must be conditioned.

Required components:

• Burden resistor
• RC low-pass filter (optional)
• Voltage divider / biasing (for ADC protection)

Basic flow:

CT Sensor → Burden Resistor → Filter → ADC Input

Burden Resistor Selection

The burden resistor converts CT output current into measurable voltage.

Formula:

Where:

Selection considerations:

• Output voltage must stay within ADC range (0–3.3V / 5V)
• Too large → saturation
• Too small → low resolution

Proper selection is critical for measurement accuracy.

Signal Conditioning and Offset

Because CT output is AC (positive & negative), ADC input must be adjusted.

Common approach:

• Add DC offset (bias) to shift signal into positive range
• Use capacitor filtering to stabilize waveform

This ensures safe and stable ADC readings.

RMS Calculation Implementation

After signal acquisition:

1. Sample ADC values continuously
2. Convert to voltage/current
3. Apply RMS calculation
4. Display or log results

To improve accuracy:

• Use multiple sampling cycles
• Apply filtering
• Calibrate scaling factor

Common Mistakes

Avoid these common issues:

• ❌ No burden resistor (dangerous for CT)
• ❌ Direct connection to ADC
• ❌ Incorrect resistor value
• ❌ Ignoring signal offset
• ❌ Low sampling rate

These mistakes can cause inaccurate readings or hardware damage.

Practical Applications

CT sensors are commonly used in:

• Energy monitoring systems
• Industrial load measurement
• Smart meters
• Motor current monitoring
• Data logging systems

Conclusion

CT sensors provide a safe and effective method for measuring AC current in embedded systems. With proper signal conditioning, correct burden resistor selection, and accurate RMS calculation, reliable current measurement can be achieved for both industrial and IoT applications.

#Sensors#
#CTSensor#
#CurrentMeasurement#
#EmbeddedSystem#
#AnalogSignal#
#TestAndMeasurement#

Current measurement is a fundamental requirement in many embedded and industrial systems. Two commonly used technologies are Current Transformer (CT) sensors and Hall Effect sensors. Each has distinct characteristics, advantages, and limitations depending on the application.

This article compares both sensor types to help engineers select the most suitable solution.

Working Principle

CT Sensor (Current Transformer)

CT sensors operate based on electromagnetic induction. When AC current flows through the primary conductor, it induces a proportional current in the secondary winding.

Key characteristics:

• Only works with AC signals
• Provides isolated measurement
• Requires burden resistor for voltage conversion

Hall Effect Sensor

Hall Effect sensors measure magnetic fields generated by current flow. The sensor outputs a voltage proportional to the magnetic field strength.

Key characteristics:

• Works with both AC and DC
• Provides direct voltage output
• Typically integrated with signal conditioning

Measurement Capability

Feature	CT Sensor	Hall Effect Sensor
AC Measurement	✅Yes	✅Yes
DC Measurement	❌No	✅Yes
Isolation	✅High	✅Moderate
Accuracy	High (AC)	Moderate–High
Cost	Low	Medium

Signal Conditioning

CT sensors require additional circuitry:

• Burden resistor
• Filtering (RC)
• Voltage scaling

Hall sensors typically provide:

• Analog voltage output
• Built-in amplification
• Minimal external components

Application Comparison

CT Sensor is suitable for:

• Industrial AC monitoring
• Energy metering systems
• High-current applications
• Electrical panel measurement

Hall Effect Sensor is suitable for:

• Battery monitoring systems
• DC motor control
• Automotive applications
• Bidirectional current sensing

Accuracy and Noise Consideration

• CT sensors provide stable readings for sinusoidal AC signals
• Hall sensors may introduce offset drift and noise
• CT sensors require calibration for burden resistor scaling
• Hall sensors require offset compensation for zero-current detection

Engineering Insight

Choosing the right sensor depends on system requirements:

• Use CT sensor for high-current AC measurement with isolation
• Use Hall Effect sensor for DC or bidirectional current measurement

For mixed systems (AC + DC), Hall Effect sensors are more flexible but come with higher cost and complexity.

Conclusion

Both CT and Hall Effect sensors are effective current measurement solutions, but their selection depends on the application. CT sensors are ideal for AC industrial monitoring, while Hall Effect sensors provide flexibility for both AC and DC systems.

Understanding these differences helps engineers design more accurate and efficient measurement systems.

#Sensors#
#CurrentMeasurement#
#CTSensor#
#HallEffect#
#EmbeddedSystem#
#AnalogSignal#

JLCONE is designed to provide a consistent and unified experience with the web platform, so users can get started immediately without a learning curve.

While the interface may look familiar, JLCONE is not just a simple “wrapper.” It serves as a centralized desktop workspace that brings together multiple JLC services—such as PCB, PCBA, 3D printing, and CNC—into one place.

Maintaining a similar interface helps ensure:

• Faster onboarding (no need to relearn workflows)
• Lower usage barriers for existing users
• Consistency across platforms

At the same time, JLCONE is gradually expanding beyond the web experience by improving integration, efficiency, and usability.

JLCONE Desktop is continuously evolving to provide a better user experience.

Future improvements may include:

• Deeper integration across all JLC services
• Improved performance and usability
• More exlusive offers than web ordering, such as more discounts, more coupons, more convenient customer service and so on

User feedback plays an important role in shaping future updates.

If there are any features or improvements you would like to see in JLCONE, feel free to share your suggestions in the community.

Placing a PCB order in JLCONE Desktop follows a straightforward process:

1. Open JLCONE and log in to your account
2. Select the PCB service from the main interface
3. Upload your Gerber files
4. Configure board specifications (layers, thickness, quantity, etc.)
5. Review pricing and submit the order

Once the order is placed, users can continue to:

• Track production progress
• Monitor shipment status
• Manage all related orders in one place

The process is similar to the web version but is more centralized within the desktop environment.