Here we replaced old relay technology with modern electronics and microcomputer. The product was built as a direct replacement for the existing relay box. Both mechanical dimensions and connectors were made exactly alike, so it was really a pure plug-in replacement. Very easy for the customer, SJ!
The task was to monitor the parameters of the engine during operation, and warn or shutdown if a fault occurs. This is to avoid that the equipment destroyed by overload or other errors. Our device can as a last resort pull down the locomotive's pantograph in full operation, but it is an absolute last hand emergency stop; the arc will be dramatic!
The new solution also has the ability to log the upcoming errors, so that the service department later can indicate how many times various errors occured.
The extremely noisy environment called for much interference suppression and filters in the deign. All inputs and outputs have surge protection and filters. The CPU is fed through a two-stage DC/DC converter, and is housed in its own shielding box, with custom filters on all I/O lines.
Nominal voltage was stated to 48V, but adding that this could vary between 18V and 96V. The device must operate as usual throughout this range; another challenge!