Typically 6.3V (AC or DC) at 300mA to 600mA to warm the CRT cathode. Note: The filament must often be floated at a negative potential relative to the main ground to prevent cathode-to-heater insulation breakdown. High Voltage (HV) Generator
Building a CRT clock involves several core subsystems that must be integrated into your schematic:
A string of high-wattage, high-value resistors (typically 1MΩ) forms a voltage divider. Potentiometers placed within this ladder allow the user to manually tune the focus anode and grid voltages. Crt Clock Schematic
, build the deflection and Z-axis first and test using an oscilloscope in XY mode. Then add the HV supply. And always – one hand in pocket when probing live circuits.
The beam is always moving. If it fires while moving from the end of "1" to the start of "2", you will see a diagonal retrace line. The turns the beam off during these movements. Typically 6
: These circuits take the low-voltage signals from the DACs and amplify them to the levels (often 100V+) required to physically move the electron beam across the screen.
+5V +12V | | [MCU] [555]--[Flyback]---> +HV to CRT Anode | | I2C GND [RTC] | [DAC]---[X-Amp]---(X plate left) (X plate right) [DAC]---[Y-Amp]---(Y plate bottom) (Y plate top) Potentiometers placed within this ladder allow the user
Maintain adequate physical spacing (creepage and clearance) on your PCB design between high-voltage sections and low-voltage digital microcontrollers.
A complete CRT clock schematic is divided into five distinct functional blocks: