Variations on Nixie Power Supply Design
Since I started tinkering with Nixie and other Neon tubes, I found the need for simple (read: inexpensive) high voltage power supply capable of generating over 170V from 5V DC.
After a bit of research I found that most of the high voltage power supply designs use boost converter driven by a PWM controller IC such as MC34063, with a high voltage MOSFET switching an inductor. (Here’s an example of the design.)
Those designs looked a bit overkill to me, so I started designing my own from scratch.
Since I’m familiar with transistor based blocking oscillator circuit to boost voltage (i.e. Joule Thief), I wanted to see if I can use a similar circuit. The switching transistor has to withstand the output voltage of 180V so I picked some high voltage transistors and experimented. Turned out that typical high voltage transistors (C-E breakdown of more than 200V) were too wimpy for the purpose, and the simple two transistor circuit that I was using was not capable of very high duty cycle demanded by high input/output voltage ratio (over 90%).
One way to reduce requirement for the boost converter is to add voltage multiplier at the output. I added a 3 stage voltage multiplier to a circuit using pretty ordinary (inexpensive) transistors. This circuit was able to provide required voltage (about 170V) and up to around 3 to 4mA of driving current to medium sized Nixie like IN-12.
After building a couple of prototype Nixie clocks using this circuit, I found a very nice transistor capable of handling 100V and 1A current.
With this new transistor, I can now reduce the voltage multiplier stage to only one, since the boost circuit itself can produce up to 100V (ok, with safety margin, more like 90V). This circuit outperformed the prior version, producing about 8mA at 170V.
Super simple HVPS using only two transistors. 180V output capable.
Simple two transistor HVPS on a Nixie clock controller PCBA. (Inside yellow rectangle – fits in 12mm x 32mm)
While I was happy with this design – especially the size and cost – and built a couple of Nixie clocks and IN-13 Neon indicator tube projects with it, I still wanted to make it better (mostly wanted more power).
If I can find a transistor capable of withstanding over 200V with a reasonably low loss, I can forgo the voltage multiplier. However the only options that I can find were MOSFETs.
After checking the prices of high voltage MOSFETs such as IRF740, I concluded that it can be more cost effective if I can make it work, since I’ll be removing two diodes and capacitors from the voltage multiplier.
After a bit of experimentation, I got it to work! Here’s the MOSFET based circuit. Note that this design needs at least 9V of input voltage to work (due to the MOSFETs gate voltage). So for the 5V powered projects, I’d still use BJT based design.
Super simple HVPS using only two transistors. 240V output capable with 12V input.
This MOSFET based design is capable of delivering at least 50mA at 200V.
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Are Nixie Tubes cool again?
I’ve been playing/designing with Nixie tubes for some time now. I found Nixies very fascinating as the numbers inside them glow just magically.
There are many Nixie Clock designs available on the net. They are usually two types; AC main powered clock without MCUs, or low voltage DC powered with MCUs. I prefer low voltage variety because of the safety reasons, as I like exposed PCBAs.
All of the low voltage designs have some kind of high voltage (180V typical) generation circuit – and I noticed that all of the designs that I see use a pretty hefty MOSFET driven by a PWM controller IC. Somewhat complex and not so small. I kept thinking – there has to be a simpler solution.
I’m sure many people reading this are familiar with Joule Thief circuit. It’s a simple blocking oscillator based boost converter. I have done some work with two transistor variation of Joule Thief extensively, and thought I should be able to use that circuit for Nixie power supply.
Looking at the basic circuit I realize that the output voltage is limited by the breakdown voltage (Vceo) of the switching transistor. So I tried testing with high voltage capable transistors. The result was not so good – you can get the voltage, but could not deliver the current Nixies needed.
So I decided to add voltage doubler to the circuit, which looked promising. After many tries with different transistors and voltage doubler or tripler combinations I was able to come up with a supply that can deliver about 7mA of driving current into a medium sized Nixie. The circuit only uses two transistors, a not so big inductor and a few diodes and capacitors. It is much simpler and smaller than all of the Nixie power supply I have come across.
It’s not as strong (only 180V and 7mA driving current as opposed to 200+V with 10+mA) and voltage regulation is not so good. However it’s more than good enough for small to medium sized Nixie tubes. It can also work with input voltage as low as 2.4V when you don’t need much output current (i.e. miniature Nixies like IN-17).
I have designed a couple of Nixie clocks using this power supply. I will follow up with some descriptions of each stage of the designs.
More Products Available at Maker Shed
I’m so excited to announce that my wearable items – A12, R48 (all colors), and USB Li-Ion Charger are now available at Maker Shed!
You can find them here.
Maker Shed also sells Color Organ Triple Deluxe II and Colour Night Joule Thief Kit.
Rustybolt.info mention of JT Blinker
Mr. Watson of Rustybolt.info blog wrote about the LED blinker circuit using Joule Thief. I’ve sent him a PCB of my prototype, named JT Blinker – multivibrator and Joule Thief combined to blink LEDs with one 1.5V battery.
He had designed a similar circuit years ago, and has some insights about this type of circuits…
Wave JT – LED chaser with Joule Thief
Wave JT is a multi-function LED chaser/scanner/sequencer. Wave JT incorporates Joule Thief to power the LEDs, so it operates on just a single AA battery.
Wave JT has over 16 sequence patterns, and speed can be adjusted by double/triple tapping the button. It’s the most compact yet versatile LED chaser.
Sequence patterns include many variation of the classic “Larson Scanner” from “Knight Rider”, random sparks, fade in/out, flashing, etc.
Even though there is only one button switch on Wave JT, you can control many things with it.
Wave JT – Kit and PCB
Wave JT is a tiny LED sequencer or “Larson Scanner” on steroid. It has over 16 sequence patterns, and speed can be adjusted by double/triple tapping the button. It’s the most versatile LED chaser.
Unlike other LED chasers, Wave JT controls each LED in smooth 7 bit (128 levels) brightness levels. The brightness curve is gamma-corrected like Aurora series, so the fades are visually pleasing.
Not only Wave JT versatile, it’s also energy efficient. Wave JT runs on a single AA battery, and the battery lasts for days!
Please view technical details and assembly instructions at instructables.
Wave JT is made with 100% through hole parts. No surface mount parts!
Kit Contents
8x 3mm or 5mm Super Bright LED of your choice
1x 4.7k ohm (R1)
1x 100k ohm (R2)
8x 39 ohm (R3-10)
1x 10pF Ceramic Capacitor (C1)
1x 0.1uF Ceramic Capacitor (C3)
1x 33uF 10V Electrolytic Capacitor (C2)
1x 47-100uH Axial Inductor (L1)
1x Schottky Diode (D1)
1x 5.1V 500mW Zener Diode (D2)
2x MPS2222A or equivalent NPN BJT (Q1-2)
1x PIC16F1823 or PIC16F1824
1x Tactile Switch (SW1)
2x Battery Clips
Note: As of Oct. 1, 2012, all Wave JT kits are shipping with preprogrammed PIC. You do not need a PIC programmer to assemble Wave JT kits!
*** Purchase Here ***
Joule Thief Kit
I’ve created this Joule Thief design back in September 2011. Now sadly I found that there’s a knock-off of my design being sold by Eastern Voltage Research. Although their kit doesn’t have a light sensor (has a switch instead), the “look & feel” of the physical design is strikingly similar to mine.
While I did not invent the circuit, I did work hard to come up with a one piece design that integrates the battery holder. I also worked hard to make it look nice.
- I’d love to know what you think of this. Please leave comments. -
To be honest I feel cheated. Things of this nature is not good for the creative community. We all strive to create something great, and when you come up with something that people like or love, one should deserve the recognition. My contacting the company failed to produce a positive result. They neither deny or acknowledge the possibility of referencing my design. Even though there are few unexplainable identicality in our designs;
- two holes at the end of the PCBs to accomodate the hook up of paper clip battery holder (The photos on their site is now photoshopped to hide these)
- The two transistors on their PCB are named Q2 & Q3, mysteriously skipping Q1, which is the ambient light sensor amp transistor in my design replaced by a switch in theirs.
Hours after contacting them, photos on their website were retouched to hide the obvious clues (mentioned above), and the manual was revised. I can only see this as acknowledgement of them copying my design. (and an effort to avoid possible legal issues…)
This isn’t about money, but it’s about giving credit where it’s due…
Colour Night Joule Thief kit Back in Stock
Thank you for your waiting. Colour Night Joule Thief kits and PCBs are back in stock.
Colour Night Joule Thief kit
Colour(Color) Night Joule Thief kit and PCB are available. Please use the buttons below to purchase.
Detailed information and building instructions are here: http://www.instructables.com/id/Colour-Changing-Night-Joule-Thief/
*** Purchase Here ***
“Colour Night Joule Thief” LED Mood Light
Detailed information including building instructions: http://www.instructables.com/id/Colour-Changing-Night-Joule-Thief/
Night Joule Thief – LED Night Light Kit
Joule Thief circuit is combined with an ambient light sensor – Night Joule Thief is a little night light that keeps going with just one battery for weeks! Two white LEDs light up surprisingly bright.
* This is the original version of Night Joule Thief that uses white LEDs – not to be confused with the new color changing version.
Please view the instructables for technical info and assembly steps.
*** NOTE: The color of the PCB will be green instead of purple shown in some of the pictures. ***
*** Purchase Here ***
“Joule Thief” LED Night Light
“Joule Thief” circuit is an inductor based voltage booster circuit to light LEDs with low supply voltage. The circuit was published in 1999 and has been quite popular. You can see the principle of the circuit here: http://en.wikipedia.org/wiki/Joule_thief
My version is a variation that uses single coil inductor, to make the inductor easily obtainable. I design the circuit using readily available parts only, to make it an ideal DIY project.
Please see the full article on Instructables (http://www.instructables.com/id/Joule-Thief-LED-Night-Light/)
