Diorama: Power Supply Completed

The main power supply circuit board has been completed, following some experimentation. The supply is soldered to a piece of copper perf board and will be mounted on the back of the facia where the power supply is plugged in.

Key features are that the power will enter the diorama via a 2.1mm × 5.5mm power socket. A bridge rectifier is used to enable both centre positive and centre negative supplies to be used.

The power supply drives a red LED that is mounted above the power socket.

A voltage regulator is used to provide a 5V supply that will be used for the microcontroller and to power the LEDs. There are output pins making available 7.9V (voltage after the bridge rectifier) and 5V, along with associated ground pins.

Here is a composite photo of both sides of power supply circuit board:

Composite photo of bottom and top of power supply circuit board

The following photo is a composite photo showing both sides of the power input panel, with the power supply circuit mounted on the rear. Note the panel wiring and the power supply board are not yet connected in this photo:

Composite photo of both sides of the power input panel

The pins shown in the rear photo are, from left to right:

  1. A pair of polarity agnostic 9V input pins. The power supply socket above the circuit board will be wired to these pins in the finished version.
  2. A pair of pins to connect the power indicator LED (7.8V and GND). The control panel LED will be wired to these. Note that the LED's current limiting resistor is wired directly to the LED. It is hidden under heat shrink.
  3. A pair of 7.8V power pins for connection to other circuit boards that may require this voltage. Note that 7.8V is the maximum available rectified voltage. (9V is dropped by 1.2V by the bridge rectifier diodes.)
  4. A rank of five GND pins for connection to other circuit boards that may require them.
  5. A bank of three 5V pins for connection to other circuit boards that may require them.

The schematic diagram of the power supply is shown below:

Power supply schematic diagram

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