Industrial Controller & Protocol Gateway
A DIN-rail controller bridging Modbus RTU, CANopen and EtherNet/IP with a 9–36 V input and 4 kV surge immunity on every port.
- Client
- Kessler Automation
- Sector
- Industrial & IIoT
- Year
- 2024
- Duration
- 22 weeks
- Layers
- 6
- Board size
- 98 × 76 mm
- Placements
- 340
- IPC class
- Class 2
Stack-up: 1.6 mm FR-4 Tg170, 2 oz outer, 35 µm inner, HASL lead-free
The challenge
Five isolated ports on one board, each requiring 4 kV surge immunity, inside a 22.5 mm DIN enclosure with no forced airflow. The client's existing product used four separate isolated DC-DC modules and could not hold its price point at the volume they had won.
Our approach
We consolidated four isolated supplies into a single multi-output flyback with independent post-regulation, which removed three modules and their footprints. Surge protection was designed per port with a coordinated TVS and gas-discharge arrangement rather than an identical circuit repeated five times, sized against each port's actual exposure. Two-ounce outer copper and a via field under the flyback carried the heat into the DIN rail bracket, avoiding a heatsink.
The outcome
BOM cost fell 31 % and part count by 46 lines. All five ports passed IEC 61000-4-5 at 4 kV line-to-earth. Sustained thermal testing at 60 °C ambient showed a 21 °C rise at the hottest component, leaving comfortable derating margin.
Measured outcome
−31%
BOM cost
−46lines
BOM line count
4kV
Surge immunity
21°C
Temperature rise
Consolidation without losing isolation
Four isolated modules exist because they are easy, not because they are right. A single multi-output flyback with a properly designed transformer and independent post-regulation gave the same isolation with a third of the footprint — at the cost of a transformer specification that had to be got right first time.
Surge protection sized per port
Copying one protection circuit five times over-protects some ports and under-protects others. We assessed each port's exposure separately and coordinated the TVS and arrester clamping so energy is shared correctly during a strike.
Thermal path through the mechanics
With no airflow available, the DIN bracket became the heatsink. Two-ounce copper and a dense via field under the switch move heat into the bracket, which is why the assembly runs 21 °C over ambient rather than needing a fan the enclosure cannot accommodate.
From the bench
Four-up panel with V-score and tooling rails for the assembler.
They took 31 % out of our BOM without touching the specification, and showed the working for every line. That is the first cost-down exercise I have seen that did not quietly move risk somewhere else.
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