IN-13 driver circuit resistor power rating

[Zachary]

Hi, does anyone know what are the minimum required specifications of the resistors R3 and R4 for this IN-13 driver circuit? The voltage rating obviously needs to be >150V but what about the power rating? 2W and 1W seem very high. I'm trying to make small PCB sockets with only SMD components but potentiometers above 0.5W are very big.

[gregebert]

These tubes draw quite a lot of power. I've only worked on the IN-9, and I recall it needed close to 20mA to get a full glow, so 1-2 watts is the right ballpark. R1 & R2 will be around 100mW worst-case, so 0805 should work.

SMT resistors put a lot more of their heat onto the PCB than a traditional thru-hole resistor because of direct contact , so be sure to measure the temperature carefully. Most PCBs (FR-4) have a glass-transition temp around 130 degrees C, so you want to be well below that for reliability.

[Zachary]

The IN-13 is only 4mA to fully light up. I think the formula for R3 and R4 is P=(I^2)(V) since they're in series and that gives less than 0.1W for both. So I could use a 0.25W resistor for them. Does that sound right or am I using the wrong formula?

[Mac Doktor]

On May 6, 2024, at 10:44 PM, gregebert <greg...@hotmail.com> wrote:

These tubes draw quite a lot of power. I've only worked on the IN-9, and I recall it needed close to 20mA to get a full glow, so 1-2 watts is the right ballpark. R1 & R2 will be around 100mW worst-case, so 0805 should work.

An always useful graphic:

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

"Would you like to see the relevant data?"—343 Guilty Spark, Halo 2

[Mac Doktor]

Forgot to include this. It may be helpful or it might simply confuse you even more:

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980

[gregebert]

4.5mA wont be a problem for a 1.5K (or smaller)  SMT resistor, because the power is 30mW (or less). I guess the 3-terminal IN-13 has a much better behavior than the 2-terminal IN-9.

[Mac Doktor]

On May 7, 2024, at 9:05 PM, gregebert <greg...@hotmail.com> wrote:

4.5mA wont be a problem for a 1.5K (or smaller)  SMT resistor, because the power is 30mW (or less). I guess the 3-terminal IN-13 has a much better behavior than the 2-terminal IN-9.

It's the "improved version". Here are some articles that delve deep into the IN-13:

https://www.saltechips.com/lab/

Very interesting.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

[Zachary]

Yes that does in fact confuse me even more. However I looked at the component list from the source of the image you sent ("M. Moores' Nixie Thermometer Kit") and he does use 1/4W resistors and not >1W like the Russian datasheet indicates so that's good.

Here's the circuit I currently have which is a mix of what I could find online. So far all of the components fit on a 25x20mm PCB (I intend on making small individual sockets). I'm using an I2C DAC (MCP4706) so that I can drive more than 6 bargraphs with an Arduino Uno (which can only do 6 PWM at once) with fewer pins. This one has 8 addresses so 8 tubes.

I'm not sure what I need for Q2 however. Should I use a second MJD340 (which is the SMD version of the MJE340 I've seen on many existing design) or any transistor will do? Or do I need it at all? Many designs don't include it for some reason. My understanding is that it's there for because of this from the Russian datasheet:

> "To avoid braking the light column when switching abruptly, we recommend: When switching on, the main cathode should not be on, and there should only be current on the auxiliary cathode."

[Mac Doktor]

On May 7, 2024, at 9:55 PM, Zachary <zacharyl...@gmail.com> wrote:

Yes that does in fact confuse me even more.

I must be psychic.

However I looked at the component list from the source of the image you sent ("M. Moores' Nixie Thermometer Kit") and he does use 1/4W resistors and not >1W like the Russian datasheet indicates so that's good.

I have the thermometer. It's designed to only travel halfway up the IN-13. Seeing as how 140V x 4.5mA = 0.63W, perhaps Mike's playing it safe with the current. Or it may play nicer with "bad" ones.

I'm not sure what I need for Q2 however. Should I use a second MJD340 (which is the SMD version of the MJE340 I've seen on many existing design) or any transistor will do? Or do I need it at all? Many designs don't include it for some reason.

Mike seems to be a fan of discrete circuits so there must be some magic going on here. You should ask him.

My understanding is that it's there for because of this from the Russian datasheet:

> "To avoid braking the light column when switching abruptly, we recommend: When switching on, the main cathode should not be on, and there should only be current on the auxiliary cathode."

I'm not sure that I've ever seen it actually done that way.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

"Every kid starts out as a natural-born scientist, and then we beat it out of them. A few trickle through the system with their wonder and enthusiasm for science intact."—Carl Sagan, Psychology Today, 1996

[Zachary]

Does anyone know what is the thickness of the leads on the IN-13? I haven't received the ones I ordered yet so I can't measure it and I couldn't find anything online.