[ index ][ back ][ site search ] [ acronyms ] [ discussion ] [ mail to a friend ] [ post message ]

Simple light bulb flasher

This circuit is possibly the simplest way to make a mains powered light bulb to flash. This circuit is an inexpensive way to make light to flasd for example in small parties and similar occasions.

Circuit features

Circuit diagram

LIVE ------+
230VAC     |
      (500mA slow)
      lamp starter  
       light bulb

Circuit operation

The circuit is simply a fluorescent lamp starter wired in series with a normal light bulb. The starter kicks in and out on a (sort of) random basis causing the lightbulb to flash on and off in a flickering sort of way.

Basically you can just wire a fluorescent light starter just simply in series with a normal light bulb but going this simpel way has it's risks. If somebody screws in too powerful light bulb you will burn out the starter (propably fire danger). This circuit uses a fuse in series to protect the circuit against serious overload or short circuits.

This circuit is designed for 5-60W light bulbs. This is what most fluorescent light starters will hanlde without problems. It is best to select a starter which has enough power rating capacity printed to it's case (many list power rating up to 60W, but some might only be designed for lower power lamps).

I have used this circuit successfully with 20W and 40W light bulbs. You can get quite nice flashing effect if you build two of this type of circuit and attach them to different color spotlights. Both of the bulbs will then flash at different rate and you will get nice multicolor semirandom flashing effect.

Componet list

NOTE: The starter should be a cheapo bi-metalic bulb type that would normally make a fluorescent light flick a few times before it lights. The electronic starters won't work for this application.

Notes on the circuit

You should try a range of values (FS-2 - FS-4) of fluorescent starters and bulb wattages (5-30W) to vary the amount of flicker. Depending the starter type and bulb rating, the flas rate and randomness varies.

Some disadvantages however are bursts of RF noise generated as the neon lamps switch. The starters typically have some kind of filtering capacitor in them, but this alone usually does not RFI may affect any radio mics or some sensitive audio equioments in the vicinity.

The starters tend to burn out rather quickly as they are not intended for this constant duty. Fortuantely those starters are cheap, so rpleacing them is not that expensive unless the circuit is intended for constant long time use.

Tomi Engdahl <Tomi.Engdahl@iki.fi>

Published by ELH Communications Ltd. all rights reserved.