The VFD and PWM drivers:

For the management of VFD tubes, I used a specialized circuit: The MAX6934.

It allows controlling up to 32 grids / anodes via a serial interface.

It allows to use a voltage going from 8 to 76V. It is possible to put several in series.

For this application, all outputs are used (4 x 7 anodes + 4 x 1 grid).

There are circuits with fewer outputs in the same family of components at Maxim integrated.

The tubes are mounted on small supports which are perfectly suited for their mechanical support and to compensate for the height of the LEDs.

These are spikes that I recovered several years ago and I can’t find the same ones. If you have a source please let me know  

For the management of RGB LEDs, I chose to use a PCA9685 circuit from the manufacturer NXP.

I have already used this circuit in several projects: The RGB clock and the Christmas tree.

It can control 16 LEDs in 12-bit PWM via an I2C bus. In this application 15 outputs are used (5 LEDs x 3 colors).

The LEDs are coupled to a MOSFET transistor.

This allows the LEDs to be supplied with 12V and does not increase the current consumption at the output of the 5V regulator.

Warning ! The LEDs are in common anodes.

The seconds LED was mounted on two LED supports. These are the same ones I used on the RGB clock. They had been bought on ebay.

The sensors and their amplification:

The clock has two sensors: a light sensor and a temperature sensor.

The light sensor makes it possible to detect a drop in light and to be able to turn off the LEDs at night (to avoid light pollution).

A setting option allows the management of the LED lighting. Three modes are available (see video).

The light sensor used is a photoresistor. It is mounted on a voltage divider bridge then amplified via a non-inverting AOP circuit.

The non-inverting assembly has a gain of 2.

The output of the assembly is connected to an ADC input of the microcontroller.

I’m going to add a setting to the clock so that I can adjust the detection level because it depends on where it is located.

The temperature sensor used is an LM35.

It has been placed opposite the power supplies to avoid disturbing the measurement in case the power supplies heat up.

The non-inverting assembly has a gain of 4.9.

The output of the assembly is connected to an ADC input of the microcontroller.

The sensor output voltage is proportional to the temperature (10mV per ° C).

This assembly can therefore be used for a temperature range from 0 ° to 100 ° C.

The sensors have been mounted with an LED support for their mechanical support. I used the same as on the seconds LED.

 The PSTN circuit:

The RTC (real-time clock) circuit allows real-time clock management. It stores hours, minutes, seconds …

The circuit chosen is a PCF8563 from the manufacturer NXP.

You May Also Like

Leave a Reply