Meshtastic HeltecV3 Hel-Txt 18650 "RUGGED"

UPFRONT!

I created a Discord channel for my Thermal vision builds but will add a #meshtastic channel there as well in case you have questions or problems. Please remain to the meshtastic channel for all sort of questions as all the other channels are ONLY for my thermal builds!

https://discord.gg/Ce9BJ2DK3j

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My try on Harukis design to transform the “consumer version” of his Hel-TXT meshtastic device into a little tank.

First thing I did was making the reset button a lot smaller as I kept pressing it accidentally. (maybe I am clumsy, but I dont see a good reason why the reset button would need to be the same size as the program button)

As I used the original design mostly outside, sunlight could cause some problems at time making it hard to read the heltecs display, that for I implemented a little sunshield above the screen, works great in direct sunlight.

GPS antenna was changed from Haruki original design to that was mounted on the outer edge of the frame, works fine but I wanted to utilize the same arrangement like on my other design I made recently. Having the GPS antenna positioned in a 45 degree angle it always points towards the sky no matter if the device is laying on its back or standing upright.

4000mAH lipo battery surely works great but I did not want to wait for the order to arrive and remixed the frame to take 2 x 18650 cells, my personal unit now features a pack of two cells with whopping 7000mAh.

Made a slot for the buzzer right underneath the mounting option on the top frame so sound can be heard unobstructed no matter if you use the TPU frame or not. Simply slot the buzzer in with the solder points exposed to the back.

The GPS mainboard also simply gets glued against the backside with some double sided tape. ( I am using nija tape as its sticks really well and stays flexible)

7000mAH is a big capacity and the heltecs onboard charging would take forever to charge the cells all the way, that for I implemented its own quick charging circuit that delivers 15Watts@5volts, which means 5 times faster charging then with the heltecs charging circuit.

On top I added 3 mounting options for ropes, carabiners, you name it, also acting as a antenna base protector (antennas with a max base diameter of 11mm are possible)

Using a peice of translucent filament as optical fiber the breathing ( status) light is well visible from all sides.

The whole build sits in a TPU printed frame that can take quite the beating, covering the on/off switch as well the heltecs USB C connector as those are not needed in every day use.

Not only does the TPU cover looks nice it also feels nice and rubbery when hand hold.

I guess that's it, gonna add a lot more pictures of the inside and how to connect GPS and make it work with a mosfet so you can switch it on/off by software ( The transistor you see on the official docu never worked for me in over 6 devices I tried, but then found a working solution with a mosfet that works reliable)

Things your going to need for this build:

PCB Keyboard:

Eingabegeräte CardKB Mini Keyboard Programmable Unit V1.1(MEGA8A) : Amazon.de: Computer & Zubehör

GPS module:

GT-U7 GPS modul navigation satellite positionierung kompatibel NEO-6M 51 ein-chip-mikrocomputer STM32 für Arduino (aliexpress.com)

3 volt buzzer 8.5x8.5x3mm

10 stücke smd Summer 5020 7525 8530 9650 1230 9032 3V 3,6 V 5V magnetischer Mini aktiver passiver Piezo-Summer Lautsprecher elektronisches Kit - AliExpress

Heltec V3 Lora dev board:

APKLVSR LoRa ESP32 Entwicklungsplatine,LoRa V3 Board mit OLED Display und Antenne USB C Dual-Core IOT Board 240MHz Bluetooth WiFi Modul SX-1262 863 928MHz für Arduino: Amazon.de: Computer & Zubehör

RGB LED: ( decide for either RED, BLUE or GREEN and use the responsible leads)

50PCS 5mm full-farbe LED RGB rot/grün/blau Gemeinsame Kathode/Anode Vier füße transparent highlight farbe licht 5mm diode bunte (aliexpress.com)

Power switch:

10/20 stücke 50V 0,5 EINE SS12F15 Mini Größe Schwarz SPDT Rutsche Schalter für DIY Power Elektronische Projekte g6 1P2T Kippschalter Griff 6mm - AliExpress

The 18650 Cells are also not protected so your going to need a BMS for each cell!

Battery management System:

10 TEILE/LOS 1S 3,7 V 3A li-ion BMS PCM batterie schutz bord pcm für 18650 lithium-ionen li batterie - AliExpress

I am aware that the Heltec V3 does include a BMS but the connected GPS will still draw power from the Heltec regardless of the BMS, this would kill your battery if the device is not switched off, that for an additional BMS connected to the battery directly will prevent this!

GPS Power switch Software based:

If you want to be able to switch GPS off and on, on demand by setting up a GPS_enable GPIO pin in the app and by pressing the button 3 times your going to need a Mosfet for that ( of course this is totally optional but helps a lot with saving power!!): SI2312

200PCS SI2300 SI2301 SI2302 SI2307 SI2312 SS8050 SS8550 MMBD1503A SOT-23 Transistor SMD Triode - AliExpress

Check pictures how you need to solder the mosfet on the heltec board, connect the ground from the GPS mainboard to the middle mosfet pin.

Quickcharge Addon charging board:

Typ C USB Eingang High Strom 3A Polymer Ternären Lithium-Batterie Schnell Lade Board IP2312 CC/CV Modus 5V Zu 4,2 V (aliexpress.com)