Neon Lamp Project: Continued

Continuing the Neon Lamp Project that I started a few months ago, I’ve put some more thought into it. I’ve decided to merge the Neon Lamp project with my Chronulator project. I’m planning to sell Chronulators constructed in vintage wood boxes with antique panel meters at SteamCon III in October this year and need to actually finalize my designs somewhat.

The stock Chronulator kit doesn’t include any output for the seconds. I want a seconds indicator, so I first designed a circuit which would alternately drive the neon flash tubes in a flip-flopping manner from a low voltage control source:

By using a pair of solid-state relays, one normally open and one normally closed, I can alternate between two 0A3 neon bulbs using a single control signal. The Chronulator doesn’t output a timing pulse of any kind, but it’s open source so I could change the code to make one. I’m taking over an unused PWM output and will be driving it either 100% full-on, or 0% full-off. Defining the PWM pin and setting a variable for it:

#define METER_S OCR0A 

 ISR(TIMER2_OVF_vect) {
 METER_M = meter_m_value;
 METER_H = meter_h_value;
 METER_S = flipflop; 

 tick_tick(); 

 update_power_mode(); 

 debounce_buttons(); 

 if( sleepModeCausesSpuriousTimer2Interrupts() ) {
 waitForTimer2CycleToEnd();
 }
 }

Start full-on, and switch between on and off each call:

static unsigned char flipflop = 255; 

 void flip_second_indicator() {
 flipflop ^= 255;
 }

and finally, in the code segment that keeps track of the seconds, a call to the actual flip-flop code:

void tick_second() {
 if( second < (secondsPerMinute - 1) ) {
 second++;
 } else {
 second = 0;
 tick_minute();
 }
 flip_second_indicator();
 }

Now, the Chronulator pushes its unused pin high and low. The Atmega168 chip powering the Chronulator can push 3V @ 20mA, which is just barely enough to actuate the control relays. I may need a small voltage amplifier of some kind to raise the 3V control signal up to a 5V level as 3V solid-state relays are a bit more expensive.

Next steps: build the Chronulator on a proto-board, then see about adding the neons to it. I also might need to add a tiny infrared emitter inside any of the boxes I build, as the neon tubes are subject to the photoionization effect and might not strike reliably in darkness if they’re mounted low in an enclosure. I’ll work out those details during prototyping.

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