I was thinking the cheapest node would be
ESP8266 ESP-07 $3 https://www.aliexpress.com/item/32965896584.html
or ESP32 WROOM $4 https://www.aliexpress.com/item/1005006336964908.html
PCB adapter $2
LLCC68 Lora module $4 https://www.aliexpress.com/item/1005004577448057.html
This in theory might be even cheaper. ESP32C3+Lora in one module for $4
https://www.aliexpress.us/item/1005005508556514.html
In theory only to connect a power supply (if careful maybe directly off batteries) and Antenna (although might need to provide a wifi/bluetooth Antenna as well as Lora one)
Edit: Seems I mispoke, I thought had read it had a onboard regulator, for something like 4-6V, but seems incorrect, (maybe it was a carrier board)
… need to supply 3.3V explicitly, So will need an external regulator to use a battery
8266 is not supported
I created a pcb arround the HT-CT62 with antennas (which can be snapped of) to get the costs down.
The BOM is:
HT-CT62 (7 - 9€)
PCB (0.8 - 1.5€)
3.3V Regulator (0.4€ - 1.5€)
The next iteration is in the mail.
If there is interest, I can make it public.
This is very cool, thanks for the idea!
You could sell as unsoldered kit on tindie.com to locals.
I more though about releasing the pcb design to the public so everybody could order some.
i would definitly be interested. Ive wondered on the practicality of a pcb antenna for lora frequencies. Interesting design
See it has placement for a usb which a plus, to make eaiser to use.
Even empty space to add a solar controller chip, which is my only other thought for a barebones node/repeater.
Something like CN3163. Know there simple boards for it, but most have leds etc, that dont need.
An external antenna would definitely be better but would also cost more. The lora antenna can be cut off if an external antenna shall be used.
I did try a PCB antenna for a 868Mhz LoRaWAN node, following one of the published designs (by Texas maybe ?). However although I had thought the PCB material was as specified for the design, the antenna did not perform at all well.
What I have used for a LoRaWAN node that works is a simple bit of PTFE wire 1/4 wave long. The PTFE wire is semi-stiff and has a very smooth hard insulation so does not snag much.
Described here;
That Heltec HT-CT62 could have wide applications in nodes that need to be small.
I have ordered a couple from Ali and also found an ESP32C3 dev board for circa £2 which would be useful for checking pinouts, I have breadboard pluggable modules for the SX1262.
The Lora and Meshtastic side works when programmend with an usb-serial interface.
Just the direct usb made problems 
Hence, the second iteration.
Looking promising!
The reference design for the HT-CT62 does include a CH340 USB-Serial adaptor (not used it, but appears simialr to CP2102), so implies the USB isnt directly useable with the ESP32 ?
Edit: seperate question why are there two regulators on the schematic? Is that just so can compare a LDO vs a linear, and choose one?
Didn’t realize the side connector was directly for a screen - cool!
The datasheet says the direct usb connection should work, also the HT-CT62 reference design.
Exactly, there are several things double populated, just pick what works best for you.
if you skip the screen and the antenna you would be looking at 7.54$ but the dip version only comes in 433mhz
I see you designed a PCB I would be very interested in cheap design with something so small with ESP32 and Lora with IPEX and if it has BMS it would be nice or USB is fine. Shoot me a message if you have something you are willing to share publicly
Another way to reduce the cost is to exclude the one time used components like
I have pushed stuff here:
https://github.com/paulhausk/CheapMesh
404 not found
Can you send me the correct one
I’m also looking into cheapest node possible…
The two bases are:
ESP32 based (as mentioned above)
HT-CT62 - but requires a baseboard with power supply.
Could be the cheapest base where power is not an issue, aka, repeater/client node in a house/vehicle, powered by usb…
NRF52840 based (Aprox $10 base cost) - remote/repeater node to rival rak’s system…
NRF52840 Development Board - https://www.aliexpress.us/item/3256805848952479.html
SX1262 Ra-01SH - https://www.aliexpress.us/item/3256802374880132.html
Would require some kind of daughter board to connect to the NRF. board could have some kind of battery circuitry for power/solar/etc …
Have a lot on my plate right now, so will keep an eye here, and contribute when I can …
