Elpro Repeater Self-Watchdog
In some instances radio telemetry systems require a repeater atop a mountain in order to have the signals relayed across the required area. Mountain tops normally lack two very important requirements, power and accessibility.
Power can be achieved by the use of solar, wind, or a combination of both. The question of accessibility is therefore the only to be addressed. It must be remembered that electronics is involved and inadvertent "lock-ups" can occur but accessibility becomes a major issue especially if all that is required is a power-down power-up cycle (total failures cannot be remotely repaired).
With some careful programming and the circuit below a power re-cycle will occur on comms failure.
Using the Elpro 105U-1 (set as Unit 10) the required mapping, as shown below, has an unused input (DI4 inverted) mapped to DO4. DO4 will therefore become active shortly after power-up. Not shown, but also programmed into the system, are the mappings of two remote units who also keep this output activated.
The timings used are important. The remote units (keeping the output updated) are programmed for 5 minute updates with the local mapping updating only every 15 minutes. The output is programmed to reset on a "no comms" at 14 minutes.
The logic is: