8.1 12 V DC power (PWR-DC12)

PWR-DC12 is the power interface of nominal 12 V DC. Its rules apply to the products that have an entry or an outlet of it, and to the cables between them:

a module with a rear DC entry;
a DC entry panel or a bus board with PWR-DC12 outlets that feeds several modules from one entry;
an enclosure with a case DC entry;
a power supply that takes 12 V DC and delivers the bus.

The 12 V DC comes from an external adapter, outside EIS, or from a power supply with PWR-DC12 outlets (SUP-009). It enters at a DC entry and feeds a DC rail, one +V and −V pair that each product filters or regulates locally (Terms). The DC rail is separate from the bus (6.4); the rules common to both power interfaces are in 6.1 to 6.3.

A product's filtering, the connectors of its outputs that are not PWR-DC12 outlets, ripple at PWR-DC12 outlets beyond what a power supply publishes (SUP-001), and the adapter it ships with are product documentation, not EIS. The rules for the person fitting a DC entry are in 9.3. The tables are in data/dc_12.json.

DC entries

A product shall publish its DC entry variant: DC-BAR21, DC-BAR25, DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 (DC-001), and the minimum and maximum DC input voltage its DC entry accepts (DC-002). It publishes the current it takes at its DC entry, and the current it delivers at each PWR-DC12 outlet, at 12 V (PWR-001, PWR-002).

The variants are of two kinds:

A module DC entry, DC-BAR21 or DC-VH2, takes the rail for one module, usually from a PWR-DC12 outlet.
A case DC entry is defined by its role, not its connector: it is a DC entry that takes an external adapter's output for a row: any DC entry of an enclosure, a power supply, or a bus board, or of a module with PWR-DC12 outlets or row wiring outputs. DC-BAR25, DC-DIN4, DC-MF6, and DC-MF8 are case entries only; DC-BAR21 serves both, a small case on a 2.1 mm adapter among them. It sits on an enclosure, which then has a PWR-DC12 entry, on a power supply, or on a DC entry panel: a module with a PWR-DC12 entry that feeds the supply, the bus board, or its own PWR-DC12 outlets, and then also keeps the outlet rules. The wires from a case DC entry to what it feeds are row wiring (6.1).

A product with a case DC entry shall publish whether its 0 V is bonded to the chassis at the entry, and where (DC-014): in a system fed from an adapter the case DC entry is where the one chassis tie belongs (6.3). EIS recommends that it make the bond, in PWR-008's form, and carry an M4 CHASSIS terminal for straps to the case's other panels.

A DC entry and each PWR-DC12 outlet shall be marked beside it with its polarity, a barrel by its polarity symbol and a multi-pin entry by its +V and −V pins, its nominal voltage, and its maximum current, and a DC entry also with the minimum and maximum input voltage it accepts (DC-011). The trade marks every DC inlet this way, so an adapter or a cable is chosen at the port.

A DC entry shall not use the pinout of a Eurorack 10-pin or 16-pin power header (DC-003). A barrel DC entry, DC-BAR21 or DC-BAR25, shall be center positive (DC-004).

Variant	Pin × barrel (mm)	Typical continuous (A)	Notes
DC-BAR21	2.1 × 5.5	2.5	Also a PWR-DC12 outlet to a module (DC-009). Jacks for a 2.1 mm plug are rated 2.5 A to 8 A by their makers.
DC-BAR25	2.5 × 5.5	5	Higher current, from an adapter, 5 A to 7 A by the jack; never an output to a module (DC-009). A DC-BAR25 plug enters a DC-BAR21 DC entry but makes unreliable contact (ASM-004).

DC-VH2 is a 2-pin JST VH wire-to-board header, rated 10 A with 16 AWG wire and its terminals, that takes power from a PWR-DC12 outlet. Above 5 A, EIS recommends DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 rather than a barrel: a through-hole jack for a 2.1 mm plug is rated 2.5 A to 8 A by its maker (Same Sky PJ-002A 2.5 A and PJ-002AH 5 A, both with a 2.0 mm pin that a 2.1 mm plug takes; PJ-063AH 8 A) and a 2.5 mm jack 5 A to 7 A with a standard plug, and the product publishes its own figure (PWR-001).

EIS recommends that a DC entry accept at least 10.8 V to 13.2 V, ±10 % of 12 V. A 12 V adapter regulates to about ±5 %, and a reverse-polarity diode, the protection of an outlet, a lead, and a jumper cable each take a few hundred millivolts on the way to the module; a product with PWR-DC12 outlets publishes the voltage it delivers at its rated current.

A product with a DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 DC entry shall implement the pin functions tabulated for that variant (DC-005). The receptacle and plug named are reference parts; an interchangeable part rated for the published current may be used.

Variant	Product side (reference)	Cable side (reference)	Rated continuous (A)	Rating basis
DC-VH2	JST B2P-VH or B2PS-VH	JST VHR-2N	10	1 contact per pole × 10 A with 16 AWG wire (JST VH)
DC-DIN4	Kycon KPJX-4S-S	Kycon KPPX-4P	15	2 contacts per pole × 7.5 A (Kycon KPJX-4S-S)
DC-MF6	Molex 39-30-1060	Molex 39-01-2060	24	3 circuits per pole × 8 A at 18 AWG (Molex PS-5556-001, 4 to 6 circuits)
DC-MF8	Molex 39-30-1080	Molex 39-01-2080	28	4 circuits per pole × 7 A at 18 AWG (Molex PS-5556-001, 7 to 10 circuits)

DC-VH2 pins

Pin	Function
1	+V
2	−V

DC-DIN4 pins

Pin	Function
1	+V
2	−V
3	−V
4	+V
5	shell (optional)

DC-MF6 pins

Pin	Function
1	+V
2	+V
3	+V
4	−V
5	−V
6	−V

DC-MF8 pins

Pin	Function
1	+V
2	+V
3	+V
4	+V
5	−V
6	−V
7	−V
8	−V

Modules with a DC entry

A barrel DC entry, and every case DC entry, shall tolerate reverse polarity without damage (DC-006). A computer supply's 8-pin EPS12V cable is a Mini-Fit Jr 2 × 4 like DC-MF8, with its +12 V on the other row: it may mate a DC-MF8 entry reversed.

A module may have both a power header and a DC entry. The rules of 6.1 and 6.3 cover it: it does not require both entries connected at once (PWR-003), and the installer connects one (ASM-003); it does not feed its DC rail onto the bus (PWR-004); and its DC rail's −V is its 0 V (GND-001). While the DC entry carries the load, its published bus currents (PWR-001) state what it draws from the bus, which may be nothing.

Cables

A straight DC barrel cable shall connect tip to tip and sleeve to sleeve at both ends (DC-007). A cable for a DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 DC entry shall connect each pin to the same pin and function at both ends (DC-008).

Distribution to modules

A product with PWR-DC12 outlets to modules, a bus board, a DC entry panel, or a power supply (SUP-009), shall feed them only through DC-BAR21 jacks or DC-VH2 headers, never DC-BAR25 (DC-009). A product with PWR-DC12 outlets to modules shall protect each output separately and shall publish the current at which the protection acts (DC-012), so that one shorted cable takes down one module and not the rail. Its own DC entry shall tolerate reverse polarity without damage and shall not pass the reversed voltage to its outlets (DC-013). Its outputs to a supply or a bus board are row wiring on M4 terminals (6.1), not outlets to modules.

A cable from a PWR-DC12 outlet to a module shall end in DC-BAR21 plugs or DC-VH2 housings and connect +V to +V and −V to −V, tip and pin 1 being +V (DC-010).