MDE175-24D12&24: Why 12V and 24V Always Show Up Together Inside Field Devices

Walk up to a standalone industrial device on the floor — a remote IO station, a field control box, a small comms terminal — and look at its terminal block. You'll see two kinds of wires: thin signal wires going to sensors and comms, and thicker power wires going to solenoids and relays.

Behind those wires are two power rails. The signal side runs at 12V — low voltage, but it has to be clean because it feeds sensors and communication circuits. The power side runs at 24V — enough current to drive relays and solenoids. A device that needs both traditionally packs two DC-DC modules inside. The MDE175-24D12&24 puts them in one.

Two rails, two jobs

Input is 24VDC (wide 18-36V range). Two outputs:

• Rail 1: +12V at up to 6.25A — powers sensors, comms modules and on-board digital circuits, ripple held to 120mV

• Rail 2: +24V at up to 8.4A — powers relay coils, solenoids and indicator lights, ripple 200mV

Each rail regulates independently. When the 12V rail steps (like a comms module booting), the 24V rail doesn't flicker. When a relay kicks on the 24V side, sensor readings on the 12V side don't jump. Both rails are ±2% accurate with ±0.5% regulation.

Why the 12V rail is held to 120mV ripple

What sits on the 12V rail? Small-signal conditioning circuits and comms module power pins. These are sensitive to supply noise — a little extra ripple and sensor readings drift, comms throws errors. That's why the 12V rail is held to 120mV P-P: not for the datasheet, but so the small-signal circuits actually work.

The 24V rail feeds relays and solenoids — switching-noise sources themselves, indifferent to ripple. 200mV is plenty. The two rails are designed around what they actually drive, not one spec for both.

One module instead of two

Replacing two single-channel modules with one dual-channel part:

• Half the mounting footprint — field control boxes are cramped

• One input harness instead of two — the 24V bus feeds one module

• One fewer SKU on the BOM

• One fewer failure point to troubleshoot in the field

Footprint is the standard MDE size: 118 × 110 × 29.5mm, rail/pin-mount.

Isolation and protection

Input-to-output isolation >1500VDC, input-to-case >1050VDC, output-to-case >500VDC. Five protections: input undervoltage, input overvoltage, over-temperature, output over-current (120% limit), output short-circuit. Field devices see dust, humidity and voltage swings that a cabinet never does — these protections are the baseline.

Where it belongs

• Remote IO stations and field control boxes: 12V for comms/sensors, 24V for actuators

• Vehicle and mobile equipment: 12V for onboard electronics, 24V for control

• LED displays and lighting: 12V for the strip drivers, 24V for the controller

• Industrial comms terminals and outdoor monitoring boxes: 12V for the main board, 24V for the external I/O

• Any field device needing both a 12V signal rail and a 24V drive rail

In the MDE 100-300W lineup, the MDE175-24D12&24 is the 24V-input, 12&24V dual-output model. The series also offers MDE175-24D05&24 (5&24V). Custom dual-voltage combinations available.

Samples and datasheets: Guangdong Mingzinc, +86 400-019-3997, shturl.cc/wirR.

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