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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Every now and then, I feel like designing something really simple and basic. Blinkies are my go to circuit for the simple LED joy. Just ten parts and the two LEDs blink back & forth…
However I always find powering the circuit a bit of pain – if I use battery, I’d have to change the battery all the time. But using an AC adaptor is kind of messy. Then I realize that USB ports are everywhere – on my computer, on the side of my keyboard, phone chargers, etc. Being able to just plug a blinky into any of USB ports around would be fun.

So here it is, USB Blinky. I used thicker PCB material so that the PCB will fit into USB port nicely making the simplest possible USB plug.

- view detailed technical info and assembly instructions @ instructables

- purchase USB Blinky

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I was doing some clean up and found some old works from years ago…

The one above is a multi-purpose PIC pad using PIC16F627. This was an exercise of multiplexing 7 segment LEDs and button matrix using the same set of I/O pins. I wrote code to make it work as a timer and organ (more like a beeper with notes). 2 AA battery holder was connected to it, but obviously lost.

This was done in April of 2003. Before Arduino and all that good stuff was available. Home etched and hand drilled PCB. What’s amazing to me now is that I designed the PCB in Adobe Illustrator! I did not have a CAD software.

> PCB Layout

Next up is my very first LED project using PIC microcontroller, which was done right around the same time as the pad above.

> Schematic
> PCB Layout

I used four microcontrollers on this one. three controlling LEDs, and another one controlling them. The center one is the “master”, sending command to the other controllers to orchestrate the animation. The three “slaves” are just controlling the LEDs as they are commanded. The setup seems more complicated than my recent projects, but back then I was literally applying “divide and conquer” method to the circuit design.
When I first envisioned this one, I had no knowledge of microcontroller. I had some electronics experience and knew how to use logic ICs, however it quickly became clear that what I wanted to do was too complicated to accomplish with logic ICs. So that prompted me to look around, which led me to BASIC Stamp. BASIC Stamp, for those who never hard of it, it’s kind of like a pre-Arduino. You can write the code in BASIC language and upload it to the chip over serial cable. It was easy to use, but the processor was very slow.
Faced by the limitation I decided to learn to code PIC microcontroller directly. It took me a while to get into, but I managed.

I made a revision of the same circuit, multiplying the number of LEDs by using a complementary drive approach. (July 2003)

> Schematic
> PCB Layout

After this prototype, I decided to move on up to manufactured PCB. Found a free PCB design software (called Osmond PCB – which I still use), and start having my PCB made by a factory. This enabled me to design with fine traces and more precision.

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This is the simplest circuit to make two LED blink back and forth. The technical term for this circuit is “astable multivibrator”.

It’s really easy to put together, with only 10 parts.

[Part List]

• 2 x LEDs – any color. Red, yellow, green, blue…
• 2 x NPN transistors – just about any small transistor. I used PN2222A, but you can use 2N3904, 2N4401, etc.
• 2 x Capacitor – around 10 – 22 uF, 6V or higher than power supply voltage. Electrolytic capacitors are the easiest to find. The larger the capacitance the slower the blinking.
• 2 x 220 ohm resisters – anything from 200 to 1k ohm of any type should work.
• 2 x 47k ohm resisters – anything from 22k to 100k ohm should work. Value of these changes the timing of blinking (larger the value, slower the blinking).

You can easily obtain the parts from your local Redioshack.

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