Neon Bulb Chase Lite Kit

Available at my eBay Store:

(Click on photo, below, to view video):


This is essentially, an updated version of the old Radio Shack Science Fair / P-Box Neon “Goofy Lite” Kit. The difference being that this one comes with its own PCB, and the high voltage generator has been replaced, from a transformer dependent blocking oscillator, to an IC based boost converter. In modern times (after 1985 or so), the newer circuit, though more complex, is actually much less expensive.

The heart of the circuit, however, remains the same. Using only resistors (2.2M), capacitors (0.22uf), and neon bulbs (IN-3), this simple circuit sequences between the neons. Sequence order (clockwise, or counter-clockwise) is random upon power up.

Below, is the schematic of the circuit (click on drawing to enlarge):


The HV boost supply is based around the established MC34063, originally made by Motorola (now ON Semi). A MPSA42 transistor is added to allow boost voltages over 40V, but hooked up in the common-base configuration, as to take advantage of the MC34063’s faster speed. This supply can deliver an adjustable voltage from 90 to 200V, with a maximum current of 4mA (at 200V). So this supply can also be used to tests nixie tubes.

The capacitors (C1-C5) are hooked up in such a way, between selected neon anodes, as to charge in a manner that will create regular sequence between the neon bulbs. IN-3 neons are currently issued with the kit, but any neons will work, just as long as they are are all the same type. Note the star hook-up pattern.

Below are the parts in the kit. Only an external 12V DC source is needed. With this circiut that “12V” can be anywhere from 9V to 18V. If no further mods or loads are added, the true current draw on the 12V, will be under 100mA.


(Click on list, above to enlarge):

Here is the assembly guide for this kit (click on drawing to enlarge):


Note: how the IN-3 neons are to be mounted. I suggest that you keep at least 1/2″ (12mm) of lead space between the neon and its board pads. Try not to bend these leads too much. Especially near the bulb’s glass body, as they are very frail, and can easily break off.

This circuit can also be used as the base for driving brighter lamps, than simple neons. Below, is a mod that will drive AC line voltage (either 120V or 220V) incandescent lamps. (click on drawing below to enlarge):


There are tap jumpers labelled CH1 thru CH5 on the board. As shipped both pads, on all 5 jumpers, are at “circuit common” (aka “ground”, but not true ground) level. If these are to be hooked up to an external driver (such as an SCR, TRIAC, or transistor), the trace between both pads (per jumper), are to be cut, on the solder side. Then the driver devices can be installed.

Also shown on this drawing, is a simple way of getting HV DC, from the AC line, instead of using the 12V to HV converter.

3 Channel Modification:

(click on drawing to view video)


If you only want 3 channels, you can stuff the board, as shown below, plus the addition of one jumpering wire. In addition, to that, you can still opt to drive external loads, as shown before, by adding SCRs (or transistors).

(click on drawing, to enlarge):


Here is the 3 channel board with NPN transistors (2N4401) used to drive LED strips:

(click on drawing to enlarge):


Follow a similar procedure as with the HV SCR Mod, but still using just 12VDC, and NPN transistors, instead of SCRs. The positive (+,red) leads of the LED strips are connected to +12V (tapped off the power jack “tip” connection (very back terminal), and the negative (-,black) leads go to their respective transistor collector leads.


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