Silicon Chip – May 2019

siliconchip.com.au Australia’s electronics magazine May 2019 47

It is designed to be powered from
a solar panel and uses a single-cell
LiFePO 4 rechargeable cell for power
storage, so it can be used where there
is no mains power available.
This is ideal as you can, for exam-
ple, mount it up on a pole, where it
will have a good ‘view’ of both the
transmitting and receiving units, and

Fig.1: the repeater circuit. Data transmissions are picked up by UHF receiver RX1 and fed to microcontroller IC1’s

RB0 input. They are then stored in SRAM IC2, and once the transmission is complete, read back out of the SRAM and

sent on to UHF transmitter TX1. IC1 then waits for a programmable delay before listening for another transmission.

Power from the rechargeable LiFEPO4 cell is stepped up to 5V by REG2, and that cell is charged from a solar panel

using charge management chip IC3.

it should also get plenty of sunlight to

keep the battery charged.

Circuit details

The circuit diagram of the repeater is

shown in Fig.1. It’s based around mi-

crocontroller IC1, the previously men-

tioned 433MHz transmitter (TX1) and

receiver (RX1), a 1024kbit/128kbyte

static RAM (IC2), plus power supply

parts such as the LiFePO 4 charger (IC3)

and 5V step-up regulator (REG2).

Microcontroller IC1 monitors the

signal from the UHF receiver (RX1),

stores the received data in the SRAM

(IC2) and then powers up the UHF

transmitter (TX1) to send out the stored

code that was previously received. IC1