Hello,
I am hoping to limit the current into a Nixie tube tube via this device.. (LR8)
View attachment 191535
I am really hoping I can make it digitally adjustable too. My project goal is to be able to cycle through the numbers and change the brightness via a smartphone/bluetooth. So my nixie tube is an IN-17 which has a current rating of 1.5mA to 2.5mA. With this device, that means R needs to be between 480 and 800. The first thing that comes to my mind is a 1k digital potentiometer, since at 0.0025A there would only be 2.5 volts at those pins (where the maximum is ~5.5v). Unfortunately, all these pots are 20% tolerance and not ideal for this situation. The 1% tolerance digital pots seem to go no lower than 20k either.
I could perhaps use the 1026 step, 1% 20k d-pot from steps 13-29 to keep the pot in the 380-800 realm. But then I need to ensure that the pot is in "performance mode" and it just seems like it's becoming way overly complicated to do this.
Is there a better solution? This is meant to be a battery powered application so I primarily wanted to minimize wasted energy over the typical anode resistors. I am super open to suggestions, such as perhaps a high-side BJT setup? I keep reading how those can be unreliable though.. I could toss the brightness adjust-ability idea, but I am hoping not to lose sight of my design goals.
Thank you for any input you have on this!! I'm at a loss at what to try next.
-Chris
I am hoping to limit the current into a Nixie tube tube via this device.. (LR8)
View attachment 191535
I am really hoping I can make it digitally adjustable too. My project goal is to be able to cycle through the numbers and change the brightness via a smartphone/bluetooth. So my nixie tube is an IN-17 which has a current rating of 1.5mA to 2.5mA. With this device, that means R needs to be between 480 and 800. The first thing that comes to my mind is a 1k digital potentiometer, since at 0.0025A there would only be 2.5 volts at those pins (where the maximum is ~5.5v). Unfortunately, all these pots are 20% tolerance and not ideal for this situation. The 1% tolerance digital pots seem to go no lower than 20k either.
I could perhaps use the 1026 step, 1% 20k d-pot from steps 13-29 to keep the pot in the 380-800 realm. But then I need to ensure that the pot is in "performance mode" and it just seems like it's becoming way overly complicated to do this.
Is there a better solution? This is meant to be a battery powered application so I primarily wanted to minimize wasted energy over the typical anode resistors. I am super open to suggestions, such as perhaps a high-side BJT setup? I keep reading how those can be unreliable though.. I could toss the brightness adjust-ability idea, but I am hoping not to lose sight of my design goals.
Thank you for any input you have on this!! I'm at a loss at what to try next.
-Chris