This module is part of my Eurorack series. It is the necessary dual voltage power supply for every synthesizer! I use it in all my projects. The PSU delivers -12V, +12V and +5V.
Buy kit or PCBs in my storeKey features#
- dual voltage -12V and +12V
- additional +5V
- 12V AC/AC 1A-2A wall wart power supply needed
- 16-pin IDC Eurorack power connector
- easy to build, all through hole components
How it works#
The power supply is based on the 78xx/79xx linear voltage regulators. The current that it can deliver depends on the used regulators, the wall wart adapter, and the cooling of the regulators. It is important that the wall wart adapter’s output is AC; DC won’t work! The kit comes with 1A regulators, and you need an 1A-2A wall wart adapter in addition. See also variations
Dimensions: 115mm x 65mm
Video#
Eurorack power system#
There are two types of power connectors in the Eurorack world. The 10-pin IDC connectors have pins for -12V, ground and +12V. The 16-pin IDC connectors have +5V, CV and a gate signal in addition. With this, control voltage and gate signals can be hard-wired between modules if supported. A lot of modules only have the 10-pin connector, and that’s why the 16-pin to 10-pin adapter cables are needed. Usually, the connectors and sockets have an arrow or marking to identify the -12V rail. This should align between the bus board, cable and module.
Assembly#
Begin with the components with the lowest profile and work your way up. All components have a fixed designator and a component value printed on the board. Additional information on the parts can be found in the BOM below. If you use heat sinks, make sure to screw them to the voltage regulators before soldering. Do not fix the regulators to one big heat sink, this will end in a short circuit! R1 and R2 are load resistors for the voltage regulators and can be left out, unless you have problems with the start-up of the power supply (*). There are two options to connect the power supply to the wall wart adapter. There is a barrel jack and a 2-pin screw terminal, which can be used to wire it up inside your casing.
Take great care while assembling the power supply! Double-check the orientation of the diodes and capacitors before powering it on for the first time. Measure the output voltages before connecting any module to it.
See the Component Basics guide for help identifying parts.
Variations#
There is a 78Sxx voltage regulator series which delivers 2A. Please note that the AC/AC adapter needs to be bigger as well if used. Make sure to use proper heat sinks or even a fan when drawing much current!
There are buck converter replacements for the 78xx regulators which can deliver up to 3A and are much more efficient. I have good results using those with a 12V AC/AC 5A wall wart adapter.
The design can also be used for a 9V or 15V dual power supply. Just replace the voltage regulators and use the according wall wart supply. Make sure the caps have a proper voltage like 35V or more.
BOM#
| Reference | Value | Footprint | Description | Qty |
|---|---|---|---|---|
| C1-C6 | 3300uF | Capacitor_THT:CP_Radial_D18.0mm_P7.50mm | electrolytic, 35V | 6 |
| C7, C8, C11 | 1uF | Capacitor_THT:CP_Radial_D5.0mm_P2.50mm | electrolytic, 35V | 3 |
| C9, C10, C12 | 100uF | Capacitor_THT:CP_Radial_D6.3mm_P2.50mm | electrolytic, 35V | 3 |
| D1-D8 | 1N4004 | Diode_THT:D_DO-41_SOD81_P10.16mm_Horizontal | 8 | |
| D9 | LED | LED_THT:LED_D5.0mm | LED 5mm | 1 |
| J1 | Barrel_Jack | Connector_BarrelJack:BarrelJack_Horizontal | 1 | |
| J2 | Connector_Generic:Conn_02x08_Odd_Even | Connector_IDC:IDC-Header_2x08_P2.54mm_Vertical | IDC 16-pin | 1 |
| J3 | Conn_01x02 | Connector_Wire:SolderWire-1sqmm_1x02_P5.4mm_D1.4mm_OD2.7mm | optional | 1 |
| R1, R2 | 3k3* | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | * only populate if you have problems with PSU start-up | 2 |
| R3 | 330 | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | 1/4W 1% resistor | 1 |
| U1 | L7812 | Package_TO_SOT_THT:TO-220-3_Vertical | 1 | |
| U2 | L7912 | Package_TO_SOT_THT:TO-220-3_Vertical | 1 | |
| U3 | L7805 | Package_TO_SOT_THT:TO-220-3_Vertical | 1 | |
| Heat sink | max. size 30mm x 13 mm | eg. SK 145/37.5 or SK 145/20 (see notes) | 3 |
Notes#
- Heat sink 20mm: https://www.reichelt.de/de/en/shop/product/heat_sink_20_mm_aluminum_15_k_w_to-220-228066
- Heat sink 37.5mm: https://www.reichelt.de/de/en/shop/product/heat_sink_37_5_mm_aluminum_12_k_w_to-218_to-220_to-247_to-24-228069
Schematics#
References#
http://musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/WALLWARTSUPPLY.php
