Lectro's Answer Desk

Hi! I'm Lectro. I fix the worn-down circuitry in the space station, and build some electronic gadgets, too. If you have a question, drop one in my inbox and I'll answer it ASAP.

[ask-lectro-the-kacheek]

Ouch... my ears hurt...

I set up the countdown device and tested it, and ended up making my ears bleed.

Well, that’s what you get for using a super loud siren on one of your projects...

[ask-lectro-the-kacheek]

Sorry, can’t tell you my favorite thing to build. I have none.

I do enjoy tinkering with those neon gas discharge readout tubes that everyone loves to use in their projects. But I must be careful, as my bench power supply can’t supply the voltage it needs, and I need a significantly high voltage to use the device. The supply only goes up to 60V, while the tube needs 170V to light, and 145V maintaining voltage.

To fix that problem, I built a high voltage power supply to supply the tube with 170V. I added a 10K resistor in series with the anode before hooking up the high voltage to limit the current going in.

Here’s the symbol for the tube:

The long line inside the oval is the anode. Connect that through a 10K resistor to +170V.

The hollow circles (numbered in this symbol) are the cathodes. Ground one of these with the anode connected to +170V to make the tube glow.

The dot in the oval indicates a gas in the tube, denoting a gas discharge tube.

I hope this helps if you decide you’re going to tinker with such a tube someday!

[ask-lectro-the-kacheek]

Sorry about the hiatus, everyone. I was building a bunch of different circuits for myself and others, some of which involved me working with voltages above 50V (which are very dangerous).

I even tinkered with some miniature 2.5V bulbs and tried to get them to flash using transistors. I seem to have managed it somehow, but I forget the schematic...

Anyway, for the upcoming New Year, I built a countdown timer with a very loud 125dB siren for its alarm. The schematic is based off of mister_rf’s shot clock design, but with a preset of 60 seconds, a larger display, and a boost converter to drive the 12V siren.

The whole system will be driven off of a 5V power supply per the specifications of the 74- series logic ICs.

[ask-lectro-the-kacheek]

If we compare AC and DC in the pain test Wally and I did together, AC is much worse.

The reason is the body has capacitive properties that allow AC through, and block DC.

Don’t try this at home; you’ll possibly kill yourself trying it.

[ask-lectro-the-kacheek]

Got any questions? Leave them in my inbox.