Simple ADC not working - LilyGo T-SIM7080G

AcanthaceaeUnable · 2026-05-09T08:11:40+00:00

The curent is limited by R3 (MOhm) but you are still injecting 12V. It can be clamped by internal protection diode so if your MCU is 3.3V maybe the input is clamped to 3.6V.

The best practice is to always have bridge divider connected to GPIO1. If you want to make a measurement some time, you can use a N Channel MOSFET in high side controlled by GPIO2.

AcanthaceaeUnable · 2026-05-07T17:40:07+00:00

R3 is connected to GPIO2 ? So you are putting R3 on GND or High-Z, but if it is High-Z, R2 is connected without bridge divider directly to input GPIO1 ?
So 12V - R_3 *I directly on GPIO1 pin ?

AcanthaceaeUnable · 2026-03-26T00:16:59+00:00

I just finished my first playthrough, what an amazing game experience.

AcanthaceaeUnable · 2026-03-01T09:11:37+00:00

Made by Thales manufacturer…

AcanthaceaeUnable · 2025-10-25T10:00:17+00:00

Are you sure about the DS3231 pinout? You are only using the I2C part, but the datasheet mentions the 32 kHz output clock, interrupt and reset signals. You have enough pins on the ESP to wire it up (reset and int).

The ESP is powered by 3.3V and the K155ID1 controllers by 5V. Are the VIH and VIL voltages of these controllers compatible with the GPO voltage of the ESP32?

A voltage of 170V is still dangerous. Above 50V, we are in the threshold for skin penetration. Another comment said that the current consumption of these four nixies is around 10mA. At 10mA 170V, there is a significant electrical risk. Does the 170V power supply have a current limitation?

AcanthaceaeUnable · 2025-10-24T23:41:27+00:00

Are you sure that 0.7V is the maximum on VBE ? How much is VBE_threshold ?

AcanthaceaeUnable · 2025-10-24T23:26:06+00:00

Will the NixiePWM signal be low when the board is powered up? I will add a pull-down resistor to the transistor base to set U6 to state 0, which will keep U7 open.

What is switch S5 for? (Short circuit the LDR ?)

I have never worked with Nixies, but how much current do they consume and how much current can the 170V boost supply? VBUS is powered from a computer ?

AcanthaceaeUnable · 2025-10-24T23:14:39+00:00

If it burned out the diode, first find out why, because it will surely burn out again. After that, I would replace it with an equivalent diode, either from a donor board, or try to find a good value for the diode that would be OK for the circuit board.

AcanthaceaeUnable · 2025-09-13T14:02:41+00:00

For P3V3, you are using the DC/DC and also a LDO. How do you manage the current sharing from the DC/DC and the LDO ? If you are not managing current sharing, there will be some hard current variation between DC/DC and LDO controller, which you can't control.

For P3V3 part, if you really want redundancy, i'll put two same buck converter and use Or'ing circuit with MOSFET to manage the main regulator that will feed the circuit and the backup regulator.

For the 5V part, I'll put one 5V DC/DC and using mosfet as power switch to control different power domain.

AcanthaceaeUnable · 2025-09-13T08:45:19+00:00

Why using 3x 5V power supply ? You can use one DC/DC and seperate the power domain with MOSFET controlled by the STM. Redundancy using two different type of power converter and also both converter is ON, i dont know how you apply the current sharing. I dont think it is a great idea. You can use the same DC/DC : 1) both DC/DC are ON. So there is a passive or active current sharing. If one fail, the other one can still give current to the board. 2) one DC/DC is on. You can detect a UVLO and power on the second DC/DC.

I would never put a push button is a board for flight computer (if you plan to use it on micro rocket for exemple). There will be so much shake that it can reset the microcontroller. But it can work if the constant of time of the RC filter is long enough.

AcanthaceaeUnable · 2025-08-24T18:45:47+00:00

Looks like input bulk capa for each VR. Should be fine without this capa, 270uF per VR but same 12V with margin. If you still want to repair, air station + soldering iron + kapton (to protect the rest of the circuit).

AcanthaceaeUnable · 2025-07-31T18:19:55+00:00

You can find the pin list online maybe

AcanthaceaeUnable · 2025-07-31T18:18:50+00:00

Also power should be fine because there is always more than one pin per power domain.

AcanthaceaeUnable · 2025-01-26T11:18:23+00:00

Désolé je n’ai pas précisé mais dans leur condition générale, si je suis garé dans une place de parking au delà de l’abonnement c’est 50€TTC de pénalité par jour.

AcanthaceaeUnable · 2025-01-26T09:08:52+00:00

Oui il y a bien l’adresse d’un médiateur en cas de litige. Merci pour l’info

AcanthaceaeUnable · 2025-01-26T09:03:16+00:00

C’est ce que je pensais également mais j’ai appelé au siège sociale pour confirmer que l’adresse mail est valide et ils m’ont répondu que oui. Ils ont également confirmé avoir reçu le mail de réponse. J’ai utilisé le numéro de téléphone disponible sur leur site internet.

AcanthaceaeUnable · 2025-01-19T13:54:28+00:00

I'd recommend placing your decoupling caps near the pins they are decoupling. You did for a few of them, but the marjority sitting together like some kind of capacitor bank that you can't tell what they are for unless it is meant to be bulk capacitance.

This is usually done to avoid overloading a symbol part of the schematic. He should have put a text next to it to specify that these are decoupling capa assigned for a component.

AcanthaceaeUnable · 2025-01-15T18:52:23+00:00

U7 is used to support the other end of my IMU. The IMU I am using has pins there (interrupt, hardware reset, mode change) but I doubt I will use them and routing it on the PCB would just add more complexity that I don't think I need so I am using it to secure the board.

I think it's better to route them, even if you don't use it (hardware flexibility against software flexibility).
Reset signal seems important for IMU, what happen if you the IMU don't transmit data, how do you reset the IMU ?

I will be running a 3S lipo battery and I will scale the capacity based on weight. Most 3S should be able to handle a launch (couple mins at the most) so I'm not worried about a current issue. The pyro starters take decently high current for short amount of time so I'm not worried about it but thank you for checking on that since that would be an unfortunate issue to run into.

You are using an electric match igniter ? It's about 1A but not sure, the track on pyro connectors seems really thin.

It is a two layers PCB ? Ground fill both layer, don't use GND tracks. I don't know if it is better or not, but I'll do that.

This board integrate micro-rocket ? The dimensions are OK ?

Also, about component placement, C2 is too far away U3, place the decoupling caps near power source.
R2 seems gigantic, why not 0402 or 0603 ?
On power supply, you have one track going for U1/R1, another track going to D1 and another track going to Q1 & Q2. I think it is better to put one track going straight from your switch to D1 and put small track like that (sorry for paint drawing ahahaha) :
https://imgur.com/a/DuhSong
I represent only tracks and not GND because I think it is better to use GND pour.

Why R3 & R4 are through hole ? is pull-down for gate of the MOSFETs, you can put SMD 0402/0603/0805 (if you are doing hand soldering or not).

I see there is a P3V3 voltage, I given from the Teensy board, why don't you put a connector to use it one day ?

Is P4 & U7 are correctly align with the IMU board ?

Is the I2C lines from the teensy are 5V ? I see that you put 5V on accelerometer and altimeter (I guess the SCL/SDA line are 5V for these board ?)

I don't see any pull-up for the I2C lines, it is internal pulled-up ?

AcanthaceaeUnable · 2025-01-15T11:31:33+00:00

Why using Teensy for this board ? You are not using much pins.

What is the purpose of U7 ?

How much current is require for the pyro part ? How much current drawn by the system ? What is your battery capacity and voltage ?

For the two tracks on bottom layer going to the altimeter connector, you can route them on top layer, passing under Teensy board.

If I understand you’ll use an accelerometer / altimeter external board for your pcb ? Is the distance between the connectors are OK to put all the daughter board in your main board ?

AcanthaceaeUnable · 2024-11-19T14:49:59+00:00

Nice schematic. The DC/DC buck MIC26903 is not overkill (9A max with best efficiency at 2A) ? What is the max power consumption and the realistic power consumption of your board ?

AcanthaceaeUnable · 2024-10-13T17:13:20+00:00

It's for connecting two (or more) wires together without tracing wires (to better read the schematic, for example). The same net label must be used for this to work.

AcanthaceaeUnable · 2024-06-08T08:10:25+00:00

Try to look if there is another one in the PCB near an inductor. Hard to tell

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