Mcu 0139-remote-433MHz-transmitter

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Home automation project sending telemetry using a low-cost ISM-band (433MHz) transmitter.

This is a change of plan from what I originally intended to use (the RFM69HW modules), but with several home automation solutions easily available I decided to make use of these modules instead.

This is the bare transmitter module.


Here is the transmitter module wrapped in heatshrink and stuck on top of an Arduino Nano

0139 Prototype-1 Arduino-nano.jpg

Making the overall form factor even smaller by contemplating putting it on a Digispark board.

0139 Prototype-2 Digispark ATtiny85.jpg

The benefit is that the ATtiny85 modules are fairly cheap and can hold up to 8kB of program memory. A quarter the size of the ATMega328 Arduino but probably still more than enough to send some telemetry.

This is the module fitted onto a custom PCB that has the ATtiny85 on the underside.

0139 Prototype-3 Attiny V1.0.jpg

Final result on top of a 3D printer battery holder



0139 PCB v1.5 schematic.png

Gerbers: File:0139-remote-sensors-433Mhz v1.4

Source code: File:0139 remote 433MHz transmitter

0139 remote sensors 433mhz transmitter bill of materials -- PCB v1.5

R1  1206  22k
R2  1206  4k7
R3  1206  1k
R4  1206  100k
R5  1206  100k
R6  1206  4k7

C1  1206  1uF
C2  1206  1uF
C3  1206  100nF
C4  1206  10nuF

U1  SOIC      ATTiny85-20SH
U2  TO-92     DS18B20 
U3  TSOT23-5  NCP718ASN330T1G

T1  SOT23  (N-Ch FET) BSS138 or Si2302DS
T2  SOT23  (P-Ch FET) NDS352AP or BSH203
T3  SOT23  (P-Ch FET) NDS352AP or BSH203

D1  1206   LED

H34A-433  ASK transmitter 433MHz 2.6-12V