Danger

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Eurorack synthesizers need a linear bipolar power supply. In order not to have to work with mains voltage, a wall-wart adapter is used for power input. This power supply will provide +-15V/1A and 5V/1A. The current for +-15V is split, there is 500mA available on each rail. For the bipolar source, a 15V AC adapter is needed. The 5V source is generated by a 12V DC adapter. The circuit is largely from the MFOS Wall Wart Power Supply by Ray Wilson.

construction

The circuit is very simple. The 15AC input is half bridge rectified. The positive half is providing the +15V, the negative the -15V. The capacitors remove the ripple and the regulators provide a clean DC voltage. The 5V regulator circuit is taken directly from the datasheet. The 5V should not be used for audio circuits. It is meant to drive LED's and as input for regulators providing the power for a microchip.

Figure 1: Power Supply Schematics

Ribbon cables and IDC connectors are used to connect the modules. The IDC connectors are 10 pins in 2 rows and a spacing of 2.54mm. The pin configuration does not follow any standard. It is not possible to connect any other module to this power supply.

Figure 2: IDc-Header Pin Mapping

construction

Figure 3: Kraft Board

BOM

kraft

#	reference	value	description
6	C1 C2 C3 C4 C5 C6	3300uF	Aluminium Electrolytic Capacitor, 35V, D=12.5 mm, LS=5 mm
4	C7 C8 C9 C10	1uF	Aluminium Electrolytic Capacitor, 35V, D=5 mm, LS=2 mm
1	C11	0.33	Multilayer Ceramic Capacitors MLCC
1	C12	0.1	Multilayer Ceramic Capacitors MLCC
6	D1 D2 D3 D4 D5 D6	1N4004	Diode_THT:D_DO-41_SOD81_P10.16mm_Horizontal
2	J1 J2	PJ-102AH	DC Power Connector
15	J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 J13 J14 J15 J16 J17	IDC Header	Pin Header IDC, 10 Pos, 2.54mm
1	U1	L7815	Positive 1.5A 35V Linear Regulator, Fixed Output 15V, TO-220
1	U2	L7915	Negative 1.5A 35V Linear Regulator, Fixed Output -15V, TO-220
1	U3	L7805	Positive 1.5A 35V Linear Regulator, Fixed Output 5V

mount

#	reference	value	description
1	D1	LED (Blue)	LED 3mm low current
1	D2	LED (Red)	LED 3mm low current
1	D3	LED (Green)	LED 3mm low current
1	D4	LED (Yellow)	LED 3mm low current
2	J1 J3	IDC Header	Pin Header IDC, 10 Pos, 2.54mm
4	J2 J4 J5 J6	CT2224	Banana Socket
2	R1 R4	2k2	Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal
2	R2 R3	10k	Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal

There are also two wall-wart adapters needed. One must be 15V/AC, the other 12V/DC. Both adapters must have one Ampere capacity.

schema

kraft mount

PCB

kraft mount panel

gerber

kraft mount panel

Figure 4: Kraft panel stacking

usage

Plugin the Wall-Wart connectors to the kraft barrel sockets. Be careful and don't mix the inputs up, both connectors have the same size. The modules are connected with ribbon cables, use one socket per module.

References

MFOS Wall Wart Power Supply (+/-9V to +/-15V)