I used to ask PCB fab house to panelize my designs, but Altium Designer has a board array feature that makes panelization very simple. Also PCBWay, my go-to PCB fab accepts panelized gerbers the same way single board designs. So I have become comfortable panelizing my own designs.

This PCB was for JT Filament – the through hole design has been available as kits, but I started offering pre-assembled version as well, so I wanted to produce SMT version for that.

The panels and the stencil were produced in two days and delivered via DHL Total turnaround was only 5 days. This is crazy fast. (No rush fees paid. Note that it’s not always so quick, but sometimes you get lucky.)

Panels and stencil delivered. Oh and the holiday gift.

I ran the first batch of 4 panels as a test. Stenciling, pick & place, and reflow went without a hitch. I was very happy.

Stencil and the PCB Panels

Using low temperature paste for reflow – to protect the filament LEDs.

Assembled and reflowed panels

After testing each circuit on the panels, I went on to break them apart… That’s when it hit me – those V-scores are not snapping like I expected. After trying out some forceful ways to break the panels and only getting two boards successfully separated, I started to panic.

I talked to the support person at PCBWay and realized that my panelization had two problems;

1. The boards were too close together (the support between the V-score lines needed wider).
2. The inner cutouts left only thin strips next to the V-score line. This part can break or twisted during the depaneling.

#2 seemed to be the major issue, and since I can’t change the board design itself, I had to change the panelization. I decided to use tab-route instead of V-scoring. Which means I will have to file away the mouse bite residue after depanelization. Oh well…

I am now waiting for the delivery of the new panels (while keeping my fingers crossed). Will post the result soon.

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HV Generator open output voltage – limited internally to under 200V. The red LED lit up to indicate the voltage limit has reached.

The Pocket High Voltage Generator that I made a few weeks ago proved to be a very handy tool. I have been testing Zener diodes very often since I use many Zeners in 12V to 91V range.

However I wanted to give it a bit more power so that I can test Nixie tubes clearly – the previous design can only give less than 0.5 mA through most Nixie tubes, some digits don’t lit up completely.

I made some upgrades to the components to give it a modest 2 – 5 mA (depending on the voltage) output. While still keeping the same form factor.

Upgraded HV Generator can comfortably drive Nixie tubes at 1 – 2 mA of current.

Now this circuit has enough oomph to shock you if you accidentally touch the output! Not the dangerous level, but it IS shocking. Perhaps one can use this as an electric Jack-in-the-box…

I’m sharing the PCB design of this project. Which can be purchased or downloaded via OSH Park.

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After receiving many requests, I finally decided to publish/share the firmware source code of A60.

I was put off by the cheap clone made available, but I now think there can be something good in sharing the firmware, so that others might learn something from my code – not that my coding skill is that good, but the way you can use a simple MCU like a PIC24Fxx to directly control the individual brightness of 180 LEDs (60 x (R+G+B)) is pretty cool, because you can same money and space by not using PWM controller ICs.

You can find the code here: https://github.com/theledartist/A60

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- There’s an update to this post, including PCB design files. -

There are times you find yourself looking for a relatively high voltage (100V to 200V often in my case) but low current DC power supply. I have zener diodes that are higher than 30V, which makes the lab supply useless, and filament LEDs with forward voltage over 60V. When I need to test them quickly, I used to hook up a simple rectifier circuit to a variable AC power supply (nothing more than a slidac with isolation transformer). While this gets job done, the setup is capable of supplying much too high current (1A or more), so I was always very nervous and extra careful in handling the circuit. All I need is a little HV generator that gives me around 200V DC and only capable of supplying a milliamp or less. Realizing that I do have such design available – one of the Nixie supply circuit – I just decided to put one together to use.

Pocket HV Generator schematics

Quick & dirty build of the tool.

A single AA battery seems to be enough to generate over 200V on the output with no load. But the output quickly lowers when you draw 0.4mA. So it feels pretty safe to handle this casually, and I can only feel a bit of tingling, not electric shock when I touch the output terminals. The tool proved to be quite handy and useful in testing variety of things:

• Zener diodes (zener voltage)
• Switching diodes (reverse breakdown voltage)
• Filament LEDs (forward voltage)
• Regular LEDs (forward voltage – yes it’s ok to use this tool, since it’ll only give less than 1mA even at 2-3V)
• BJTs (breakdown voltages)
• Neon & Nixie tubes (not very bright, but you can tell if one works or not)

Pocket HV Generator testing a zener diode

Pocket HV Generator testing a Nixie tube

This is one of the most useful tools that I’ve made. And it only took a couple of hours to put it together.

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Added a new project to Instructables on headphone amp. This is something that I have made to improve my music listening experience during my subway commute.

- See the instructable

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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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Only part that needed developing was the high voltage power supply. I did not want to use mains AC as the power source, and ideally wanted to use 5V DC so that the clock can be powered from USB.

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. A large MOSFET switching a good size inductor. 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 wanted to see if I can use 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 (I’d estimate close to 99%).

One way to reduce requirement for the boost converter is to add voltage multiplier at the output. I added a 3 stage Cockcroft–Walton multiplier to a circuit using pretty ordinary (inexpensive) transistors. This circuit was able to provide required voltage and up to around 3 to 4 mA of driving current to medium sized Nixie like IN-12.

While this power supply was not quite powerful enough for larger Nixie tubes, I went ahead and designed a clock circuit to get my feet wet.

First design was a 4 digit clock using ATMEGA328 – I wanted to make the software easy to develop, so I loaded Arduino boot-loader. I also wanted to use the clock as a multipurpose numerical display so I added a V-USB port.

This prototype had some stupid bugs, but the basic functions such as multiplexing worked. I made a revision of this prototype right after.


Here I experimented with a tapped inductor to effectively double the boost converter output voltage and do away with voltage doubler instead of tripler.

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As a part of developing new projects, I make PCBs for prototypes. I usually use OSH Park to have my prototype PCBs made. They are great – sophisticated web ordering page compete with full preview of the PCB design, which has helped me notice the errors before ordering. Low, no-gimmick pricing – just $5/sq. inch for a set of three PCBs.

Since I don’t always use all prototype PCBs, I have a few PCBs laying around. Some of them contain errors (that’s the point of prototyping, right?), but most of them (lucky for me) are perfectly functional.

So I want to give away those good prototype PCBs. The schematics and BOMs are provided on this site or instructables already, so you can gather parts and build them!

The qualification is simple – give me/my site a mention and a link on your web site, or if you have made any of my designs, put up a project at instructables (with pictures or/and video). Let me know what you did by either leaving a comment here or email, and I will send you a PCB. (Free shipping within USA only – sorry, international shipping will cost $5.)

I have more than a few good PCBs for the published and unpublished designs. Offer is limited to while PCBs last.

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Here’s the new project that I’ve been working on.

Aurora 48 has 48 full-color/RGB LEDs, each individually controlled. Each and every 48 LEDs has 7 bit per channel = 2,097,152 possible colors. Like other Auroras brightness curve is gamma corrected so the fades are very smooth.

Using all SMT components, Aurora 48 is compact and low profile. 2.68 inch (68 mm) in diameter and only 0.137 inch (3.5 mm) thick.

Aurora 48 inherits most of its circuit from other Auroras before it. The controller is PIC24FV16KA304 (same as Aurora 18×18), however doubling the RGB bus by the help of a binary decoder chip (74HC238).

- Schematic-rev3a

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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…

> read the article at Rustybolt

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