Forum - Recent Threads

Woohoo!! My first chip antenna PCB design works successfully!

arvindsa — Thu, 19 Feb 2026 05:29:34 GMT

For my Hack the Holidays, i was trying to make a Christmas tree Earring. It did get stuck in for almost an eternity, but it did arrive, Then i kept it procrastinating because i was working on my Connect 4 Game. But yesterday, when i set up my soldering station (I have a tiny room so its a portable setup) i decided to solder the earring too. Now, this was the first time i am making a PCB with a chip antenna. In my Light Up your life, i managed to make a Inverted F antenna, but there i had the liberty of the PCB size. This one, the PCB is small like around 40x20mm, so it had to be chip antenna. I had many NRF52832 and chip antennas in my drawer which i bought and never used. I was fighting against many factors that can make the PCB not work -

Old components may not solder well
Incorrect Design of Matching network components
Incorrect PCB Routing including deviation from the 50Ohm Impedance.
ESD Damage
Random Silly mistakes from my end.

This is a two layer board and based on Kicad's impedance calculator i had used nearly a 3mm wide track for the 50Ohm impedance path. In Hind sight thats half the size of the NRF52 Chip itself.

But Against all odds. one of the boards worked unconditionally. The second was not showing up the BLE beacon. It was a example program from Nordic. But assuming a cold solder, i took it to my university and blasted them with hot air to flow them with a good flux and boom.. The beacon worked. I got a more than 10m range with them. That's the farthest i could go without losing Line of sight in the room. Was so excited that i had to share this.

Now on to more things..

P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

arvindsa — Wed, 18 Feb 2026 05:49:18 GMT

I’m using a DMP2045U P-channel MOSFET as a high-side switch to control 3.3V power to an ESP32-S3-WROOM module. The gate is driven by an STM32.

Connections

Source → 3.3V (measured 3.289V)
Drain → ESP32 3V3 pin
Gate → STM32 GPIO
10k pull-up from gate to 3.3V

Measurements

When gate is LOW (~0.009V):

Source = 3.289V
Gate = 0.009V
Drain = 3.289V
Vgs ≈ −3.28V → MOSFET turns fully ON (as expected)

When gate is HIGH (3.287V):

Source = 3.289V
Gate = 3.287V
Vgs ≈ 0V → MOSFET should be OFF

However:

Drain measures ~2.89V

I added a 47k pulldown resistor from drain to GND. This reduced the drain voltage to ~2.4V — but not to 0V.

All STM32 GPIOs connected to the ESP32 are driven LOW.
If I completely remove the MOSFET, the ESP32 3V3 rail stays at 0V (no floating voltage).

Question

Is this expected off-state leakage/floating behavior for a discrete P-MOSFET in this configuration, or is there something wrong with my circuit?

E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

robogary — Tue, 27 Jan 2026 03:08:15 GMT

The RC Hammering Rubber Duck in the Tub has been officially entered into the Fun & Games competition.

I wanted to share some final comments about our robotics club program, Ducks with Hammers, for the Mysticon SciFi convention in western Virginia this past weekend.

Attendance was a little lighter than normal with a major winter storm hitting the eastern US. Another collegue who drove in from Illinois is still in Virginia waiting for roads to be cleared.

One colleague, who was driving from Florida to Virginia, turned around and headed for home with his Ducks with Hammers after hearing the weather forecast. We missed battling those Ducks.
The convention's guest of honor was Gigi Edgley, best known for her portrayal of Chiana on the science fiction series Farscape. She stopped in to say hi to us during our program and check out our robots and projects. She is a really nice lady.

The RC robots are usually the big hit. The RC Hammering Rubber Duck was no exception. A close second was this robot I built in about 30 minutes. Nicknamed the Scrambler, it had a plywood base cut from scrap, with a roller underneath the rear, 2 continuous servos hot glued to the base, interfaced to a radio controller transmitter & receiver. A 100 rpm gearmotor ran continuously coupled to an old mixer beater.
For next year's convention , we're thinking to focus more on building a fleet of combat robots from kitchen utensils and maybe one autonomous project each.

Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

arvindsa — Thu, 15 Jan 2026 14:32:48 GMT

The PCB has been delivered. I got some parts enroute and in that time ive got to thinking. Should I code in Arduino or Should I do in stm32HAL? I have my pros and cons listed. For now my only strong reason to stick to Arduino would be because I intend to make this open source and want others to tinker with it

If you were developing this, why would you choose stm32hal ?

E14 Fun & Games - 1st public trial for the RC Hammering Rubber Duck in the Tub

robogary — Sat, 10 Jan 2026 01:00:49 GMT

https://youtu.be/wvT1RfBScMA a short video of the fun

January 5th, the Radio Control Hammering Rubber Duck in the Tub ( a Fun & Games E14 project not posted yet)

had its first showing for a homeschool's Intro to Robotics class.

The vehicle steering and hammer servo get their PWM control signal directly from the Flysky 3 channel RC FHSS receiver.

The throttle PWM is wired to an Arduino and converted to 0-100% duty cycle PWM with direction bits.

The Rubber Duck includes a DFPlayer for tunes and sound effects. The hammer has tilt switches mounted to play the hammer sound effects.

The Duck has an arcade like target with an IR receiver at the bullseye. Using a TV remote ( Im using a star trek phaser TV remote) to fire at the Duck, if the IR receiver sees the 38kHz IR burst, it disables the Duck for 10 seconds, sounds an alarm, and the duck flashes red.

The Arduino controls also the lights, alarms, and audio effects.

The SciFi convention is in 2 weeks, still working on reliability and performance improvements.

Looking forward to finally posting these projects at the end of January.

E14 Fun & Games - Down a deep bunny hole again with the battery of The RC Hammering Rubber Duck in the Tub

robogary — Thu, 08 Jan 2026 21:13:13 GMT

The RC Hammering Rubber Duck in the Tub has its first public exhibition on January 5th for a homeschooling group's "Intro to Robotics" class.

The class is compromised of about a dozen middle and high schoolers. I was invited to bring a couple projects to class to get the students excited for the spring semester.

The students had a blast just driving the Rubber Duck up and down the hallway. I'll publish the video after I climb out of this bunny hole.

I noticed tho the battery didnt last as long as I thought it should have, and was really sluggish on a short pile carpet.

Early on in the design, I had used a lab bench power supply to check behavior at different voltages and record amps while running.

The wheels were lifted off the floor, but the gearbox and wheels were still attached, so would be somewhat close to full load running.

AT dead stop, the idle load current varied from 200mA @ 10V to 400mA @ 12v.

12V of course ran the fastest, and had the highest load 1.5A in forward , 2A during acceleration.

The Rubber Duck uses a 3S (11.1v) 1500mA Lipo Battery. I try to stick around 12V for projects, so I can use 12V wall warts, LipOs, and/or AA or AAA batteries during test runs.

First down the bunny hole to check on the LipO battery rating. It is a IRAHobby 3S 11.1V 1500mAhr 45C battery.

battery BUNNY HOLE TAKEAWAY #1

Altho load vs voltage measurements were taken using a bench power supply, the data isnt enough to reflect real load conditions while

running around on different terrain and surfaces.

I've installed a DVM and 10A DC ammeter on the Rubber Duck to collect better load and volts data while running.

The running load is close to 3A and it seemed only a couple minutes running sucked the battery down to 10 ish volts after a full recharge.

Battery is 5 years old, hardly used. Conclusion is old crappy battery.

Have a couple more batteries on order, 2200mA hr rather than 1500mAhr, and 35C rather than 50C.

Battery BUNNY HOLE TAKEAWAY #2

------> I should run a battery voltage monitor into the Arduino or Raspberry Pi for my Lipo based projects (using a voltage divider)

for a 3S battery, vigorously flash a low battery alarm at ~10V to indicate a low battery , and then to shutdown into an alarm mode when the battery gets ~ 9V

see evaluation below

Referring to and https://www.ufinebattery.com/blog/understanding-c-rating-on-lipo-battery-your-in-depth-guide/

this 1.5A mAhr battery with 45C should be able to deliver peaks of 67+Amps. Spec checks good.

https://www.ufinebattery.com/blog/3s-lipo-battery-guide-from-voltage-basics-to-full-charge/

A well-maintained 3S LiPo can last 150 to 300 cycles. If abused, it may fail after just 30 to 50 cycles.

Voltage Type	Value per Cell	3S Total Voltage
Nominal Voltage	3.7V	11.1V
Fully Charged Voltage	4.2V	12.6V
Storage Voltage	3.8V	11.4V
Minimum Safe Voltage	3.0V	9.0V

https://yungbangpower.com/blog/lipo-discharge-curve-beginner-guide/

The Typical Curve—A Quick Mental Picture

2. Plateau (Main Zone):

This is your main usable power. For most packs, 3.7V to 3.3V per cell.
Performance is strong—this is your “happy” running stage.

3. The Knee & Rapid Drop:

Just after 3.3V/cell, the curve falls FAST. This signals the battery is running out.
This is your cue: LAND your drone or stop driving now—don’t squeeze out the last bit!

4. Cutoff (Critical Danger):

Below 3.0V/cell: serious risk of permanent battery damage, swelling, or even fire hazard. Never go this far.

If you only remember this: Never run your battery past the “knee” to the bottom. Always land or stop before it nosedives.

Connect4-On-The-Go Part 1 - Planning for Improvement in V2

arvindsa — Sat, 03 Jan 2026 10:53:18 GMT

I love playing board games with my girlfriend and "punishment" for the loser. I am still trying to get her to learn swimming for the game she lost couple of months ago. One of our absolute favorite is connect 4. I had made a version on PCB for us to play.

www.youtube.com/watch

I had made the version 1 using another competition as excuse. We truly enjoyed the concept, but there was couple of mistakes which i made rendering the device more of a novelty game rather than the intended to go device. The second video is an updated casing. so, this time learning from my mistakes as well as usability issues i decided to make the 2nd version with the following changes/improvement

Make the device game specific. last time i made it multipurpose (Nebula wall art and pixel frame) for a competition purpose. it still serves well for those purposes
I want to make the device smaller. V1 PCB was around 210x210mm making it less portable and making cases on my Ender S1 Pro was very difficult, i had to hack it to print more than the standard print area
I Dont want touch. We both prefer the haptics of a click
Fix the battery circuit. Last time i made a mistake with battery circuitry and would only work on the USB-C cable attached. Effectively breaking the "on-the-go" function
I want to have ESP32 to enable over the internet play, but will use STM32F103 as main, to conserve battery.
I also want to make the PCB cheaper to manufacture. The 210x210mm was expensive, so this time i made it modular that way anyone who wants to recreate this, can chosse any LED or LED Strip of their choice. I am gonna go with Wurth LEDs. I fell in love with them because of the seriously awesome reliability. But as i said before, you can use any other LEDs
PCB to be made in white Solder masks, helps make the light at projection plate more uniform and hide the hotspot better.
Improved button placement.

Will be posting my updates soon.

Something's cooking...

obones — Tue, 23 Dec 2025 17:05:49 GMT

This wasn't as easy as I would have liked, but here I am:

https://youtu.be/wzR5DovSDmY

This is running on a MAX32666FTHR board, with SD card reader and BMI160 accelerometer+gyroscope chip, connected to a 8x8 WS2812B array

I'm not sure how I'll call this project, but at least now it can display a GIF file read from the SD card and load another file with a single tap.

E14 Fun & Games: Quick Peek of the Sharky PixyCam Chase Tank

robogary — Tue, 23 Dec 2025 02:25:40 GMT

Altho the Sharky PixyCam Chase Tank has a dysfunctional PixyCam (my fault ) its still part of my Fun&Games project. I'm feeling mischievously jolly for the holidays so here is a sneak peek of the Tank's completed build.

E14 Fun & Games : Sneak Peek of The RC Hammering Rubber Duck in the Tub

robogary — Tue, 23 Dec 2025 02:16:48 GMT

I'm waiting for good action videos at a SciFi convention before submitting the Radio Controlled Hammering Rubber Duck in the Tub to the Fun&Games project, but I'm feeling jolly for the holidays so here is a sneak peek.

E14 Fun & Games : The RC Hammering Rubber Duck in the Tub and the EX-Chase Tank Shark

robogary — Wed, 17 Dec 2025 03:25:02 GMT

As a quick refresher from previous Forum posts on this project:

The RC Hammering Duck in the Tub is a radio controlled Rubber Duck in a Tub ( truck chassis inside ) using an Arduino Nano to translate the radio receiver's servo PWM signal to a PWM signal & direction bits to control the H bridge. Steering had a DC motor, now uses a standard servo. The Nano also controls a DFPlayer Mini for the sound effects. When the Duck is moving, it quacks. When the hammer swings, a tilt switch wired back to the Nano will fire the HAMMER IMPACT audio file.

The Hammer is controlled by a third channel on the RC transmitter/receiver.

A carnival style duck target on board, the bullseye has a hidden IR receiver. When the target gets hit from a Star Trek Phaser ( IR TV remote) , the Duck turns red, and the RC is disabled for 10 seconds.

To make things even more interesting, there is a companion robot Chase Tank, with an inboard plastic shark on top. It is guided by a PixyCam to chase the Duck.

The Chase Tank was completed hardware wise, but the Arduino code was not producing good results in tracking the Hammering Rubber Duck in the Tub.

To ensure the Duck could be uniquely identified, white LED strips were installed around the tub circumference. This really helped to make the Duck Tub standout, and it could be identified in Pixyam (verifying thru the PixyMon screen) up to 15 feet away ! YAY !! The LED rings and strings really add a drain on the Lipo battery tho.

.........But Disaster is always looking over success's shoulder. I've been pouring over the setup trying to figure out why my code doesnt work correctly.

I failed the PixyCam. Im not sure what exactly did it: the stalled tilt servo that made smoke come out of PixyCam, accidentally plugging in a 11.1V 3S Lipo rather than the 7.4v 2S Lipo, or plugging in the SPI connector backwards repeatedly on the Arduino Nano.

I had to unplug the locked up tilt servo. The PixyCam blocks transmitted to Arduino were ColorCode blocks CC, even tho there is no CC config setup. If I removed battery power from PixyCam powering strictly from Arduino, the Arduino would stop seeing CC blocks, and report back signature blocks (YAY!!) except the x y coordinated never changed, width & height = 0.

For now, Chase Tank will be put in a drawer because I now I want to upgrade it to true object detection.

E14 Fun & Games : The continuing adventures of the RC Hammering Rubber Duck in the Tub and the Chase Tank Shark

robogary — Wed, 10 Dec 2025 02:23:16 GMT

For your holiday entertainment:

RC Hammering Rubber Duck has been finished several times. I cant keep my hands off making tweaks. The last task will be defining the game rules.

The public demonstration at the community college robotics competition has been rescheduled 3 times due to snow and freezing rain maybe someday I'll get a video in action.

I may also have a chance to demo to a home schooler class before the SciFi convention.

The Chase Tank picks her animal theme: Shark -> because sharks can eat ducks and sharks are more generally menacing than a crocodile ->

Version 1 used an Arduino Uno Rev 4 , but discovered the Arduino PixyCam library (being nearly 10 years old) is not compatible with the Arduino R4. PixyCam did suggest a header file fix, but I had already moved forward to Ver 2 by then.

The Chase Tank Shark Version 2 uses an new bootloader Arduino Nano R3, and the old PixyCam header files worked. YAY ! The protoytype was kinda acting flaky while testing tho.

I added 3 diagnostic LEDs to display the main operating modes:

1) Stopped by PING SENSOR when there is an obstruction in the way. Tank treads attempt to run and climb over obstacles, not always the best thing for walls and table legs.

2) Target (Duck) seen by pixycam and the chasing ensues

3) pixycam Searching for target (Duck)

The diagnostic LEDs did not behave as expected or needed. Hours of troubleshooting and adjusting variables, just seemed to make it worse. The PixyCam Target acquired LED and the Search LED are mutually exclusive, but often were lit at the same time. The ping LED fast flashed, which meant it was processing bad data.

I concluded the ping sensor code and SPI library do not play nice together, the fix to be Version 3.

Version 3 The Chase Tank Shark splits functionality using qty 2 Arduino Nanos. One Arduino Nano is dedicated to PING sensors mounted on the front of the Chase Tank. The PING s Arduino Nano output is the STOP by obstruction LED, which is also wired back to the PixyCam's Arduino Nano as an input.

The PixyCam's Arduino Nano also controls the Tank H bridge. This version is still under test.

The PixyCam is a Rev 1.3 dated 2013. It's blob detection does not reliably differentiate colors especially under differing light conditions, that why the Rubber Duck sits on a 4 watt white LED ring.

However, the PixyCam will mistake a lit table lamp as the duck. Lucklily, places where these robots get demonstrated dont have table lamps.

I'm considering a PixyCam2, which advertises object detection, as an improvement step, but also wonder if NiclaVision could be even better using OpenCV and extensive model training.

I was pleasantly surprised as Charmed Labs product support provided some insightful advice on PixyCam and PixyCam2.

One Charmed Labs recommendation is to upgrade the Chase Tank Shark PixyCam to latest firmware. I often "freeze" FW updates once projects are working to avoid bricking them and adding unused complexity. Its a habit I developed at work, where software tools had updates and bug fix releases released seemingly monthly, that had no benefits for the products we worked with.

We'll see how Chase Tank Version 3 turns out.....

E14 Fun & Games : The build adventures of the RC Hammering Rubber Duck in the Tub

robogary — Wed, 26 Nov 2025 15:52:32 GMT

Scope creep and spec changes haunt the RC Hammering Duck.

The bad news first:

Murphy's Law - plenty of spare IOs to start out ====> digital IO is nearly used up. I'd cry the blues to have to rewrite the code to use arduino analog as digital inputs and do rewiring.
No matter how many power distribution points are provided for power supplies and grounds to eliminate daisy chains, there arent enough. Add more, not enough again. Put some daisy chains in the wire harnesses, still run out. arrgghh

In spite of strategically placed blocking diodes, when I downloaded new code with main battery power on, opps, the electrons found a sneak path thru the IO and buck power supplies

and the Arduino Nano let out a nice cloud of smoke. Luckily only the Arduino suffered as a sacrifice to the project gods.

Interesting News, the RC Hammer Duck in a Tub Prototype to be demonstrated at the December 2025 Va Western Community College Invitational Robotics competition.

https://www.virginiawestern.edu/news/2022/12/22/virginia-western-robotics-competition-helps-students-glimpse-the-future/ link describing the 2022 competition.

I'll take a video and post if it ends up happening.

The Good News:

The prototype is basically operational, the Duck moves forward & backward with limits, and steering.
While moving the Duck quacks. There are 2 hidden buttons to play songs Disco Duck and Rubber Duckie.

the hammer hammers and has a hammer sound effect using edge detect on hammer handle tilt switches.

Wood spacers with washers glued on top allowed a foam board top to go overtop the controls, held in place with small magnets.

A Duck Target was added to the Hammering Rubber Duck, with a VS1838 IR receiver at the bullseye.

I had build an IR LED 38kHz Burst pulse stream transmitter on another Arduino Nano to test the prototype receiver circuit. I was thinking to build a "Laser Pulse Cannon" to mount on the chase PixyCam tank.

After testing and writing some Arduino code, found the POWER ON button on every TV remote in the room must use a burst pulse to wake up the TVs, and they also triggered the VS3818 Arduino code.

** New idea ** rather than the chase tank disabling the duck with a laser fire, why not involve another user to interact with the game.

While one person is operating the RC Hammering Rubber Duck, allow another person to try to disable the RC Duck for a short time by a disguised IR remote as a WDD (Weapon of Duck Destruction), allowing the

autonomous Chase Tank to catch up to it.

When the Rubber Duck is disabled, the Rubber Duck white lighting turns off, a red light underneath turns on, sound funeral music plays, and some disabling of the Rubber Duck happens.

The functionality depends on leftover IO space, space for more parts on the Duck Tub, and what looks like good fun.

E14 Fun & Games Project Launch - RC Hammering Rubber Duck in a Tub & the PixyCam Rubber Duck Chase Tank

robogary — Wed, 19 Nov 2025 18:26:44 GMT

This project competition isn't really due until March 2026, but here come the holidays in November and December pushing out project build time.

My Fun & Games project entry will be part of a fun STEM presentation called "Ducks with Hammers" at the Mysticon scifi convention https://mysticonva.com/ in late January 2026.

It needed to get fleshed out now, so here are the specifications:

1. The RC Hammering Duck in the Tub is a radio controlled truck chassis using an Arduino Nano to translate the radio receiver's servo PWM signal to a PWM signal & direction bits to control the H bridge.

The Nano also controls a DFPlayer Mini for the sound effects. When the Duck is moving, it quacks. When the hammer swings, a tilt switch wired back to the Nano will fire the HAMMER IMPACT audio file.

The Hammer is controlled by a third channel on the RC transmitter/receiver.

The Nano also limits the FWD & REV speeds because the main power is a 11.1 V Lipo battery , and the original truck chassis was 6 or 7 V . The chassis steering is upgraded from a hi impedance DC motor to a standard high torque RC servo.

The design includes a main fuse, a main power switch, and a motor power switch so the Duck can be turned on without any chance of the wheels turning. There will be several buck P.S. for 11V to 6V for servos and 11V to 5V for DFplayer.

The Rubber Duck will be illuminated from underneath to make sure it is seen from a distance. There are a couple pushbuttons hidden so the DFplayer can play "Disco Duck" and "Rubber Duckie".

Kids will have fun driving and hammering with the Hammering Duck in a Tub........

.....but thats not all.........

2. The Hammering Duck is accompanied by an autonomous HERO vehicle (or a VILLAIN vehicle depending on your viewpoint of a hammering Duck as virtuous or as a scoundrel) called the PixyCam Rubber Duck Chase Tank .

The PixyCam Rubber Duck Chase Tank will autonomously seek out the RC Hammering Duck in the Tub via PixyCam. Can the Tank find the Duck ? Can it catch it ? What will the Tank do to the Duck ?

Will the Duck Hammer the Tank ? That all remains to be seen. The PixyCam will provide the relative location of the Duck and its pixel(block) size from front center. Havent decided if tank steering will be by bang-bang regulator or PID.

The Tank speed is alot slower than the Duck, but the Tank will not stop unless it detects an object in front of its treads (using ping sensors). I'm thinking the use an Arduino R4 for the tank CPU, using the R4 LED matrix to show when its locked in to the Duck or searching for the Duck.

The Duck Chase Tank in continuous and relentless pursuit of the Duck will be entertaining.

Now that I've spilled the beans, what kind of crazy features do you folks think could added to these robots for more childish sparkle to the STEM show ?

Ready for Fun & Games? Join the Competition!

JoRatcliffe — Wed, 01 Oct 2025 12:52:01 GMT

I'm very excited to launch our latest Project14 competition and wanted to create a space for general discussion on the competition.

You can share your project progress, discuss challenges with each other as well as your successes and solutions.

Plus, feel free to discuss any competition details here too. Don't forget this competition closes 1st March 2026. You can also send me a direct message if there is anything you would like to ask.

Can't wait to see what everyone creates!