i use the Classic Clock and use the hv-output to drive one or two ins-1 tubes as seperator. this works fine. but when the clock runs in dimming-mode by low daylight the ins-1 runs still with the same power and shines to bright.
is it possible to connect the hv-output to the dimming?
I've taken a look into Ian's Classic Clock Rev4 Schematics: I assume the dimming is done on the anode side. So I see the following options that would require no code changes:
1. Generate the new signal on the low voltage side
You OR the six anode signals together and feed them into another EL817C. This could be a wired OR with diodes (you should then take care not to overload the controller's outputs when driving two photocouplers in parallel). Or if you dare to do this modification you may disconnect the cathode side of the photocouplers (pin 2) from GND, connect them together and to the anode side of an additional EL817C (pin 1) of which you connect the cathode to GND then. You need to adapt the resistors then for the additional voltage drop of 1.2..1.4V. This additional EL817C should then provide you your required HV.
2. Generate the new signal on the high voltage side
Same idea - build a wired OR of the outputs of the photocouplers with fast Si diodes and use this new HV output. But take care - you most likely will need another type of photocouler then because of their maximum collector current rating.
Hi Sven and Torsten,
I'm pretty sure the "Tick" LED or Neon dimming is controlled on the cathode side. In the case of neons the anode is connected to 170v, and in the case of LED's the anode connects to unregulated Vin. My Classic clock has LED's and the separators dim with the digits.
What I suspect is the series current limiting resistor is not of high enough resistance to show any dimming with neon separators.
May I suggest trying a 220k - 330k series resistor with the neons instead of the suggested 56k - 100k resistor. I've found even the 100k resistor to be too small and cause dimming of the digits when the "Tick" neons reach full brightness.
Edit: 220k -330k seems to work well with IN-1 tubes but INS-1 may require some experimentation to determine the ideal value.
Just wanted to mention... INS-1s are notorious for behaving badly - flickering, dropping out suddenly, just generally unstable - when you try to dim them. So be careful what you wish for!
I agree that higher value resistors are needed. However, with INS-1 there is a fine line between "high enough - looks great" and "too high - instability ensues".
Edit: Yes the dimming is most definitely done on the cathode side by PWM. The anodes are tied directly to the HV supply. The HV supply voltage is NOT varied for dimming or anything else. Once the initial calibration is done (at first start-up after a factory reset) the HV supply voltage is always held constant.
Look into it later when the dust is clearing off the crater.
the origin idea was to get a hv-output which is dimmed similar the tubes, so i can use a INS-1 which will also be dimmed.
I was assuming there could be an "special row" added in the firmware or something.
Now i see its still a tap of the hv-circuit.
it was just a question of interest cause dome people asked about this point.
btw: 200 kOhm was fine to glow nice for the INS-1 without flickering.