KI also installed plenty of 'security' at the USB port:
K
K(1) TVS DATA LINES
TVS Diodes protect the USB data lines against voltage transients.
(2) TVS 5V POWER
A larger TVS diode is placed on the 5V power incoming from the USB connector to deflect voltage transients.
(3) ZENER 5V + (4) FUSE
A zener diode of 5V6 (I took a bit of margin) is connected to the 5V USB power line. A permanent overvoltage will short through this zener diode and burn the fuse. The rest of the circuit should be fine.
(5) PMIC 500mA
A
TVS Diodes protect the USB data lines against voltage transients.
(2) TVS 5V POWER
A larger TVS diode is placed on the 5V power incoming from the USB connector to deflect voltage transients.
(3) ZENER 5V + (4) FUSE
A zener diode of 5V6 (I took a bit of margin) is connected to the 5V USB power line. A permanent overvoltage will short through this zener diode and burn the fuse. The rest of the circuit should be fine.
(5) PMIC 500mA
A
AP2141WG-7 chip lets only 500mA pass through from the incoming USB power to the rest of the board. In case of overcurrent it will shut down and lit the ERR LED.
FThat sounds wayyyy overkill for such a cheap microcontroller
FLike for me personally I think replacing the microcontroller itself would be cheaper
T@Wired & Wireless Networking folks, any suggestions on the best MQTT client software to use when testing MQTT topics during development? At least as far as ease of use and security are concerned..?
Amqtt explorer is what i prefer for the ease of usage
TNice! Thanks. I'm looking into it. Looks like it checks a lot of boxes around open source, platform support, and decent enough documentation, BUT...
Is it still being maintained?
https://mqtt-explorer.com/
Is it still being maintained?
https://mqtt-explorer.com/
TAlso, how and from where do I know Thomas Nordquist 
... I can't put my finger on it...
... I can't put my finger on it...
UEven I use MQTTExplorer daily but when working with sensitive applications, especially for security where we need to upload files (.crt, private or public.pem etc). I prefer MQTTFx. For a mobile client, also recommend looking into the MyMQTT App if security is not a concern
TCosts $$ 
UYes, unfortunately, *MQTTFx *costs $ starts at 49.90€. For free as Abhishek said MQTTExplorer is good to get the job done!
DCongrats @Deepak ! You've been Verified!
S@Deepak Welcome , Can you tell us a little about yourself and your technical background? What brings you to DevHeads? What are you working on currently?
DCongrats @topgun3237 ! You've been Verified!
S@topgun3237 Welcome! will be happy to know your technical background and what project you're working on these days.
KHi @fwen ,
I understand your point. However, all that protection is not so much to safeguard your "investment" in the 10-cent MCU. It's intended to safeguard your time investment. See, a Transient Voltage event (eg. ESD discharge) can damage the chip slightly, such that some of its IO pins no longer work. You might not immediately figure out why your project is failing and be troubleshooting for a whole day.
I understand your point. However, all that protection is not so much to safeguard your "investment" in the 10-cent MCU. It's intended to safeguard your time investment. See, a Transient Voltage event (eg. ESD discharge) can damage the chip slightly, such that some of its IO pins no longer work. You might not immediately figure out why your project is failing and be troubleshooting for a whole day.
Foh i thought when it's damage it just no longer work. i havent had any failed on me before. thanks for the clarification!
GAesthetics 
P@kmulier ESD diodes on IOs on a dev board is not really required.
KGlad you guys like the aesthetics.
Why are ESD diodes not required on IO from a dev board?
Why are ESD diodes not required on IO from a dev board?
Pwhy do we need ESD diodes?
P- to protect from static charge
YInvalid arguments provided: No matching combo found
Pdev board is expected to be used in lab, which is a controlled ESD safe env most of the time
Pso ESD diode is not really required but not harmful
Pif you are anticipating risk of damage then we have more risk on all switches, where a person will be touching frequently
Pone more thing I sucpect your switch and a few passives are very near to the mouting holes, please check if someone try to use screw with head, it will not touch or come very near
Pdid you use fuse after 5V TVS?
Pit should be USB 5V>Fuse>TVS
Pplz check
K@pallavaggarwal :
- The screw holes are 6mm in diameter, with a 3mm diameter hole. The head of an M3 bolt is usually not more than 5.5mm. So this should be fine.
- The switches themselves are in plastic. So, I suppose an ESD discharge wouldn't happen there? Or should I put a TVS diode on the switch contacts?
- This is where I put the Fuse:
K
KAs you can see, I deliberately put the TVS Diode right at the USB connector. So a voltage transient doesn't even get the chance to enter the board.
KThen I put the fuse.
KThen I put a zener diode that will burn the fuse by shorting a permanent overvoltage.
KA typical case would be a faulty charger that outputs 20V instead of 5V on the USB VBUS line. Normally, a charger should only output more than 5V after a protocol has been processed with the downstream device. But in case that fails, you can potentially have 20V on the VBUS.
The zener diode will short that to GND, thereby drawing a huge current. The zener (and the traces on the board) can't sustain that kind of current for long. That's where the fuse comes in the equation.
The zener diode will short that to GND, thereby drawing a huge current. The zener (and the traces on the board) can't sustain that kind of current for long. That's where the fuse comes in the equation.
KI chose a 2A fuse instead of a 500mA one, because the 2A fuses have a lower resistance in normal operation. I already cause somewhat of a voltage drop with the
AP2141WG-7 protection chip. I didn't want to create yet another voltage drop with the fuse.P- why do you get static charge on a comb? rem school experiment?
P- fuse might be good but even TVS, zener is over design. 5.1K on CC1/2 will make sure 5V only is coming from USB
K- Right, I'll put a TVS on the switches. Good point
5.1KonCC1/2should indeed make sure no more than 5V is coming from the USB. However, I've read that some faulty chargers can at times still output 20V when defect. I just wanted to account for that - even though it's highly unlikely. I'm somewhat paranoid when designing a PCB
Pin my point of view nothing is really required for 2/3 both
Prest is your call
PFaulty charger, earthquake are not required to be considered for a dev board
are not required to be considered for a dev boardKMaybe I should put a lead box around it to protect it from cosmic radiation
KWant to keep my 10 cent MCU alive at all costs.
KKThe indestructible Tiny Scarab will be known as the Nokia of dev boards. You can use it as a hammer or a screwdriver. 
NSuggesting to make it RadHard and flamethrower proof as well.
KCool. Will do.