Hi, I'm trying to build a Nixie Clock but I wanted to add brightness control trough PWM.
I'm not great with elecronics but I thought that connecting 170VDC and the PWM signal to a MPSA42 might do the trick.
Currently, I drive the Nixies with K155ID1 drivers and PCF8574 expanders.
The problem is that I don't know if other components are needed like pull down resistors.
Thanks.
From datasheets I saw on google for K1551D1, no outputs are turned if you put 0b1010 to 0b1111 on the inputs (numbers outside of 0 to 9).
So write your code to send one of those codes briefly every 25mS, how long you send it for will determine how dim the display gets.
CrossRoads:
From datasheets I saw on google for K1551D1, no outputs are turned if you put 0b1010 to 0b1111 on the inputs (numbers outside of 0 to 9).
So write your code to send one of those codes briefly every 25mS, how long you send it for will determine how dim the display gets.
That's an interesting idea! Will it be fast enough?
Thanks.
Who knows? Depends on what the rest of your code is doing.
I would think it's better than trying to switch 10 170V lines on & off after the Nixie driver chip.
The outputs on the K1551D1 or the 74141 is able to handle approx. 65 volts. By "blanking" the chip the outputs will see a higher voltage and the tube will glow, not turn off as you want.
Simply, you cannot blank using this technique. You need to blank them with an anode-transistor.
// Per.
If you have 170V or whatever on the common pin of the tube, and you stop pulling the individual pins low, then both sides of a digit will be 170V and the digit will be off.
The driver has an open collector output, not a 170V high drive output. Can add pullup resistors (to 170V) if you want to really ensure they are high when not driven. I don't think that is commonly done tho.
Hi, I tried to drive the anode with an MPSA42 at 285Hz but it doesn't reduce the brightness when I change the duty cycle. Do you have any tips?
Generalardj:
Hi, I tried to drive the anode with an MPSA42 at 285Hz but it doesn't reduce the brightness when I change the duty cycle. Do you have any tips?
Show us a schematic.
// Per.
I tried this one:
Instead of using the ne555 to generate the pwm I use the digital output 9 with modified frequency.