The LCDuino-1 display I/O processor

Preface

The LCDuino-1 can be used in many applications and configurations, it's not possible to document every case. This section covers the most common usage, namely, as a controller for the δ1 stereo attenuator and δ2 stereo input/output selector boards in an audio amplifier; and as the controller for the γ3 DAC.

The internal layout of your enclosure is an important factor to good performance. The placement and orientation of the boards and routing of wires must be carefully considered.
  • LCDuino-1 does not emit a strong RFI, but it is prudent to keep a good distance between the digital and analog circuitry. Since LCDuino-1 with its display module will typically be mounted on the front panel, it is therefore logical to locate the analog circuitry toward the rear of the enclosure, close to the input and output jacks. The δ1 and δ2 have snap-apart digital control and analog board sections to help in tight situations. The γ3 backplane board is likewise designed to be located against the rear panel.
  • The power transformer(s) should be placed far away from analog circuitry to prevent hum, preferably in a separate enclosure.
Most connections in the LCDuino-1 system use Molex KK 254 connectors. The Molex KK 254 crimp housing and terminal accepts wires up to 22 AWG. You should use 22 AWG stranded hookup wires for all power, ground, and potentiometer motor wiring. For all other LCDuino-1 wiring, 24-28 AWG stranded hookup wire is sufficient. Please do not use solid wires as they may become fatigued and break.

J7 and J8 on the LCDuino-1 board are currently unused. They are for future expansion.

System wiring for LCDuino-1 with δ1 and δ2

The following is a wiring diagram for an unbalanced system using one δ1 stereo attenuator board and one δ2 stereo input/output selector board. A balanced system will require two δ1 and two δ2 boards. Virtually all connections are done via Molex KK 254 connectors for easy disassembly. You will need to build the wiring harnesses first.

Notes:
  • J3 is normally used to supply power to the LCDuino-1 system. Only pins 1 through 3 are used for this purpose. However, this connector is also used for flashing new firmware. To do so, you must unplug J3 and insert the 6-wire FTDI TTL-232R cable instead (See Compile and flash the firmware for details). The δ1 and δ2 boards are powered through the I2C/PWR/GND harness from the LCDuino-1 board.
  • If you are building the α10 stereo pre-amplifier, the α10 backplane board takes the place of some of the wiring. Please see the α10 website for details.
  • Do not connect the J4 (I2C/PWR/GND harness) to the δ1 and δ2 boards and power up the system, unless the LCDuino-1 has the Atmel MCU pre-flashed with Volu-Master firmware!

System wiring for LCDuino-1 with γ3

The following is the wiring diagram for the LCDuino-1 in a γ3 DAC. For easy disassembly, virtually all wire connections are done with Molex KK 254 connectors on both ends.

Notes:
  • The LCDuino-1 gets its power from the γ3 backplane board via the J4, the I2C/PWR/GND connector. J3 is therefore unused for normal operation. However, this connector is also used for flashing new firmware. To do so, be sure to first disconnect the LVDD power supply from the γ3 board, then insert the 6-wire FTDI TTL-232R cable into J3 (See Compile and flash the firmware for details).
  • If you are using the ε31 bridge board, it takes the place of most of the wiring. Also, some connectors used on the LCDuino-1 and γ3 boards are different. Please see the ε31 forum thread for further information.

Motorized potentiometer wiring

The potentiometer wiring detail for the Alps RK16812MG099 is shown below. Click on the image to see a larger version. The potentiometer's body should be grounded to the metal chassis via its panel-mounting nut. If your panel is non-conductive, then you should add a ground wire.

Power supply wiring for LCDuino-1 with δ1 and δ2

It is assumed that you have a "constantly-on", regulated 5V DC power supply for the LCDuino-1, δ1 and δ2 boards. A good candidate would be the σ25 power supply. See the overview page about power supply requirements.

Note that there are two power transformers. The T2 power transformer (powered as long as the AC cord is plugged in) feeds a σ25 power supply with 5V DC output, providing power to the LCDuino-1, δ1 and δ2 boards. The solid-state relay, controlled by LCDuino-1, switches the AC mains power to the T1 transformer, which supplies power to the amplifier circuit.

Power supply wiring for LCDuino-1 with γ3

It is assumed that you have a "constantly-on", regulated 5V DC power supply for the LCDuino-1 board. This power supply will also provide power to some circuitry on the γ3. A good candidate would be the σ11 power supply. See the overview page about power supply requirements.

Note that there are three power transformers. The T3 power transformer (powered as long as the AC cord is plugged in) feeds a σ11 power supply with 5V DC output, providing power to the LCDuino-1 and a portion of the γ3. The solid-state relay, controlled by LCDuino-1, switches the AC mains power to the T1 and T2 transformers, which provide power to the γ3 DAC analog and digital circuitry.



AMB's reference γ3 used an R-core transformer with multiple secondary windings for a combined T1 and T2, and a separate toroidal transformer for T3. As with the reference γ3, it is recommended that you use a separate chassis for the power supply, to eliminate any potential hum due to transformer magnetic field interference.


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