Nixie IN-14 Brightness

[Ardjan Doci]

Hi everyone, I'm new here. I'm trying do build a Nixie Clock with an Arduino, some I/O Expanders and Russina Drivers.
I would like to adjust th brightness with the Arduino but I don't know how to do it and what is needed.
Can someone help me? Thanks.

[SWISSNIXIE - Jonathan F.]

Yes this can be done by PWM, check for PWM Pins on your Arduino.

Here is schematic for it: "uC" would be the pin where you have to connect the Arduino PWM pin.

http://renaud.schleck.free.fr/images/anode_control.png

[Ardjan Doci]

Can I wire 8 Nixie lamps to the Nixie Anode? Should I have one of these modules for each nixie?
Thanks.

[SWISSNIXIE - Jonathan F.]

Both is possible, but personally i would do one of these for each.

[marta_kson]

The schematic on taht link is CRAP! You will blow some components if You try!

It is imperative to have a resistor between the collector of NPN and base of the PNP. Otherwise it will end up in a short circuit when the NPN conducts. Google around for high end nixie drivers and You will find correct schematics.

Use one high end driver for all the tubes if You don't intend to multiplex them. Each driver puts load on the HV and is bad. Releases heat and puts extra strain on the HV-supply. The total current for 6 tubes and two small neon bulbs will be well below the limit for the transistor. Select a resistor at least two times what saturates the transistor according to worst case on it's data cheet. If left unsaturated it will become quite hot and break.

Use a fairly low PWM frequency. Without mux 100Hz is more than enough. Too high just makes the driver hot.

[SWISSNIXIE - Jonathan F.]

You say you want to use arduino? So the frequency of the pwm will be 490Hz or 980Hz. It is possible to change that, but be carefull, chaninging the pwm frequency may mess up functions like millis().

[Ardjan Doci]

Sorry for the late response but I'm afraid i can't follow you. I searched for high end nixie drivers but I couldn't find it (or I missed it).
Can you explain what you wrote in an easy way? Thanks.

[David Forbes]

Ardjan,

The common term for this is 'anode driver'. The anode driver controls the tube
anode, so it needs to operate at +180 volts relative to the Arduino. Designing
such a circuit is tricky.

I made some clocks many years ago that used a Motorola microcontroller instead
of an Arduino, but the hardware is basically the same. The anode drivers are Q1-Q12.

http://www.cathodecorner.com/nc600ab.gif

You can substitute MPSA42 for the ZTX458, and MPSA92 for the ZTX558.

Also, ignore the power supply. It was built with a custom-made transformer that
I used in my scope clocks.

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[John Rehwinkel]

Sorry for the late response but I'm afraid i can't follow you. I searched for high end nixie drivers but I couldn't find it (or I missed it).
Can you explain what you wrote in an easy way? Thanks.

One simple approach I use often is a device known as an optocoupler for the anode drive.  These work by containing an LED (which is operated by your controller) shining on a phototransistor.  They provide solid isolation between the high voltage and your CPU, they're easy to drive (like any other LED), and can even provide current gain.  They tend to turn on and off a little slowly, so they're not useful for very high speed multiplexing, but for ordinary multiplexing and PWM dimming, they're fine, and the slower edges can reduce both electrical and audible interference.  You need to choose units that can withstand your anode supply voltage, and carry enough current for the tubes they're switching.  One suitable candidate is the Fairchild FOD852, which is easily available, costs 80 cents (US) in single quantities, is housed in a breadboard-friendly 4-pin DIP package, and is good for 300 volts and 150mA.  Note that the minimum guaranteed current gain is only 10, so you shouldn't count on driving a lot of large tubes at once with just one of these, but for most purposes it'll be quite sufficient.

- John

[Roddy Scott]

Here is part of a schematic of a PV Electronics FunKlock showing opto isolators in use. You could adapt your circuit as previously said to drive the opto isolators and minimise loading issues. I am no electronics expert but it would seem to be a possible solution to your issue.

Drawing is on general release and is for information only.

[Ian Sparkes]

I also like the Opto-Isolator anode drivers. It's super simple and I've never had one fail.

I use high speed multiplexing (with an inner loop of 1000 counts in code) for dimming and tube management, and it works well.

If you want to have a look, you can find manuals here:

http://www.open-rate.com/Manuals.html

and code here:

https://github.com/isparkes/ArdunixNix6/tree/master/ardunixFade9_6_digit

I'm selling these, and after many hundred sold, the design has turned out to be robust.

Questions welcome!