Hey everyone,
First time posting here, don't know why I waited so long to join!
I'm currently working on a nixie clock project and I assembled my first unit a couple of weeks ago. Everything was going pretty smoothly and I managed to program it completely and it worked for a while. This is not my first electronics project (designed from scratch a VFD tube clock and some arduino-based data logger stuff before) but I consider myself a beginner.
Suddenly the clock wasn't working anymore. I did some post-mortem and found out that the 5V regulator had fried and the 3.3V was getting very hot.
Here is the design which you can check:
https://oshwlab.com/krizzli/nixie-clock-in-14Now disclaimer: I know I messed up and didn't connect the regulators tabs to a copper fill to dissipate heat. My mistake! But I'm not sure this is exactly the problem (yet) and I plan on adding radiators as workaround. There are probably other design mistakes, I'm sure some of you will point them out
I'm using 2 variants of the AMS1117 low dropout regulator, one for 3.3V (for ESP32 and USB to TTL chip) and one for 5V (HV5122 drivers and logic level shifter), both getting an input of 12V (which is needed for the high voltage board I'm using, which generates the 170V for the tubes). The datasheet specifies a maximum input voltage of 15V for those regulators so I should be good, right?
So anyway, I started assembling a second unit, making sure to check everything along the way and to avoid frying anything.
I got the board partially assembled (anything that jlc had in their "basic" parts) and only added the power input jack and USB connector (there are no ICs except for the two regulators): see picture
With the board unplugged, when measuring the resistance between GND and 3.3V, I get a reading of around 300 Ohms. And between GND and 5V I read around 400 Ohms.
Is that expected? I checked the rest of the board and couldn't see anything out of the ordinary. I checked my first (partially fried) board and they read almost exactly the same, resistance-wise on the regulator outputs.
Anyway, I tried to connect 12V on the input side, and checked the output of the regulators. Getting
almost 9V on the 3.3V regulator, and
10.8V on the 5V regulator.... ?
When assembling the first board, I remember doing the same and checking the outputs, which were in spec (3.3V and 5V, respectively). Did I get some duds? Did I do something wrong in the design or assembly? Is it expected that they provide the right voltage under more load?
Hopefully someone can shed some light so I can keep going with my troubleshooting and hopefully get a working board in the end.
Thanks!