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How to Make Any Light a Strobe Light Using Just Two Transistors

If you feel strobe lights very interesting but are disappointed by the fact that these wonderful light effects can be produced only through complex xenon tube then probably you are quite mistaken.

It is very much possible to make any light a strobe light if you are equipped with a proper driving circuit capable of handling different lighting devices to generate the desired strobe light effect.

The present article shows how a circuit as basic as a multivibrator may be modified in different ways and made compatible with ordinary bulbs, lasers, LEDs to produce spectacular light pulses.

A strobe light may be used for warning, scientific analysis or as an entertainment device, whatever may be the application the effects are simply dazzling. In fact it is possible to make any light a strobe light through a proper driving circuit. Explained with Circuit Diagrams.



Difference Between Flashing and Strobing

A light when made to blink or flash indeed looks pretty eye-catching and that’s the reason why they are used in number of places as a warning device or for decorations.

However a strobe light in particular may also be considered a flashing light yet is uniquely different from ordinary light flashers. Unlike them in a strobe light the ON/OFF pattern is so optimized that it produces sharp dazzling pulsed flashes of light.
There’s no doubt why they are mostly used in conjunction with fast music to enhance a party mood. Nowadays green lasers are being popularly used as a strobing device in party halls and gatherings and have become hot favorite among the new generation.
Whether it’s LEDs, lasers or an ordinary filament bulb, all can be made to flash or rather strobe using an electronic circuit capable of producing the required pulsed switching in the connected lighting element. Here we will see how we can make any light a strobe light using a simple electronic circuit.

The following section will acquaint you with the circuit details. Let’s go through it.

Pulsating any Light to Produce Strobing Effect

Through one of my previous articles we came across a nice little circuit able to produce interesting strobe effects over a few of the connected LEDs.

But this circuit is only suitable for driving low power LEDs and thus cannot be applied to illuminate big areas and premises.

The proposed circuit allows you to drive not only LEDs but also powerful lighting agents like incandescent bulbs, lasers, CFLs etc.

The first diagram shows the most basic form of a multivibrator circuit using transistors as the main active components. The connected LEDs can be made to strobe by suitably adjusting the two potentiometers VR1 and VR2.

transistor strobe light circuit

The above circuit forms the base for all the following circuits through some suitable modifications and additions.

Using a Flashlight Lamp as Strobe Light

For example if you want to illuminate and pulsate a small torch bulb using it, you would just need to do the simple modifications as shown in the second diagram.

Here by adding a PNP power transistor and triggering it through the collector of T2, a torch bulb is easily made to strobe. Off course, optimum effect is achieved only through proper adjustment of the two Pots.

strobe circuit with motorcycle bulb

As already discussed already in the previous section, green laser pointers are pretty popular nowadays; the diagram illustrated shows a simple method of converting the above circuit into a pulsating green laser pointer strobe light.

Here the zener diode along with the transistor works like a constant voltage circuit ensuring that the laser pointer is never supplied with a voltage higher than its maximum rating.

This also ensures that the current to the laser can also never exceed the rated value.

This the zener and the transistor functions like a constant voltage and also an indirect constant current driver for the laser.

laser pointer strobe light circuit

Using AC 220V or 120V Lamp as Strobe Light

The next diagram shows how an AC mains lamp may be used as a strobing light source using the above circuit. Here a triac forms the main switching component receiving the required gate pulses from T2’s collector.

Thus we see that through the above circuit designs it becomes very easy to make any light a strobe light simply by doing the relevant modifications within a simple transistor based circuit as exlained in the above examples.

Parts List

R1, R4, R5 = 680 Ohms,

R2, R3 = 10K

VR1, VR2 = 100K pot

T1, T2 = BC547,

T3, T4 = BC557

C1, C2 = 10uF/25V

Triac = BT136

LEDs = as per choice

Police Strobe Light Circuit

police strobe light circuit

For the slow astable use the following parts:

R1, R4 = 680 Ω
R2, R3 = 18K
C1 = 100 μF
C2 = 100 μF
T1, T2 = BC547

For the Fast astable use the following parts

R1, R4 = 680 Ω
R2, R3 = 10K
preset = 100K
C1 = 47 μF
C2 = 47 μF
T1, T2 = BC547

SHARING IS CARING!


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!



71 thoughts on “How to Make Any Light a Strobe Light Using Just Two Transistors”


  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. hello sir, thanks for your effort so far . i went through the second diagram concerning where the gate should be connencted is in between R1 AND R4 or before R1 and R4 . the link you shown me about increasing the frequency, i scean through it yet i didn’t figure out anything. pls i really need your help on this few question above.

    • You can change the capacitor values to change the frequency. The mosfet does not need to be Darlington. Mosfet gate can be connected directly to the collectors.

      since you have already tested the circuit with LEDs, the circuit has to oscillate and the transformer will make a low buzzing sound that will confirm its oscillating.

  3. sir pls don’t be bore with my question. 1. so the gate of the mosfet will be connected to the output of this circuit where the Led bulb is .2. like you mention darlington iRf540 should be used can’t iRf3205 be use for the job. 3. the circuit was built with 9v battery, so what if one use 12v battery won’t it blow the whole circuit .4. what and what can be change in other to increase the frequency, because what i use is fixed resistor which 100k. 5. the diode you mention which side will be connected to the gate nor the source. 6. how will i know that the transformer is oscillating. I’m waiting for Ur respond

  4. sir i build this first circuit and it work, so how can i use it as an inverter. sorry to quote you . I would recommend you to first build a basic astable circuit with LEDs as shown in the first diagram from this article and then apply it or the inverter function: don’t use VR1, use 100K for the base resistors initially so what next to do thanks.

    • Youngking, if you have confirmed with LEDs, so now you can link the Darlington power BJT or mosfet with the two halves of the astable. I would recommend IRF540 which can be directly linked with the collectors of the respective BJTs. Make sure to attach protection diodes across the D/S of the mosfets.

      After this switch ON power and you’d find the transformer oscillating at the set slow rate, may be 1Hz. Now you can gradually increase the frequency to 50Hz and get the required results.

    • You can use any resistor between 1K and 10K since the TIP122 is a high gain transistor. I have not shown resistors for the LEDs, assuming they are 12V rated or they have their own internal protections.

  5. Hello sir, I cant get a 100k pot in our local market. I got a rotary switch having six fixed similar resistors (switch used in small emergency led light pack as dimmer). Can I use this switch as a pot buy replacing all six resistor with 15k resistor (each step will increased by 15k ohm as switch rotate) for above circuit???

  6. Does anyone have a good place to get the parts in order to make this? Also, approximately how much would the parts to make this cost? I was thinking more of the 120V version. The 120V version would allow me to take a bank of LEDs that is connected to 120V plug I plug into the wall…and in theory if I plug it into this circuit then this device into the wall, would cause that bank of LEDs to flash rather than be on steady, right?

    • Hi Wesley, In India the cost of the parts would be less than a dollar, not sure about other countries. Yes the last circuit would allow you to illuminate lamps specified to work with 120V AC

      You can buy the parts from any online electronic spare parts store, although the shipping charges could be 20 times higher than the actual cost of the parts

  7. Sir,

    I have successfully built the 2nd circuit i it works but how can i make it blink slower and i have set the VR2 in maximum and its still blinking fast. Do i have to increase the 100k pot? thanks..

    Paul

  8. Hello,

    Which of this circuit well power 12v LED to use as signal blinker for a motorcycle? And as replacement for my broken flasher in my motorcycle?
    Thanks..

    Paul

  9. Hi Sir, I am a begginer in this and don't even know about the symbols or short forms of parts used in the schematic diagram. So, please kindly help me in this. I am interested in making a simple Led strobe with simple parts. So plz sir kindly send me circuit diagram with full names of parts and their values. Bcoz i can't understand above circuits of strobe lights.I will be very thankful to you for helping me.

    • Hi Anshuman, here's the parts list for you

      Parts List

      RESISTORS, 1/4 WATT

      R1, R4, R5 = 680 Ohms,

      R2, R3 = 10K

      POTENTIOMETER

      VR1, VR2 = 100K pot

      TRANSISTORS
      T1, T2 = BC547,

      T3, T4 = BC557

      CAPACITORS (ELECTROLYTIC)

      C1, C2 = 10uF/25V

      Triac = BT136

      LEDs = as per choice

  10. Hii sir, I am interested in using your circuit for speed measurement( Application of Stroboscope) so will it work for flashing light at high frequency and provide sharp light pulses at variable rate I.e at 0.5 ms to 100 ms? Please It'll be so kind if u can help me…

    • Hi Yakub, yes it will definitely work…you can try the second design from top….make sure to connect a 1N4007 diode in series with the emitter of the PNP transistor to ensure total switch OFF of the connected lamp

  11. Hi! i´m try to use this for an OFF/ROAD led cubes in my vehicle andmanage to make it work eleminating "R4" but still the leds do not illuminate to their maximun capacity and sometimes they stop being strobes, these led cubes are 12v but do not specifies the watts, Iknow they are hig wattage, could you please help me with this dilemma? thanks in advance

    I use 1/2w resistance

  12. I've noticed that some strobe circuits are better than others. Better, I mean sharper transient response. I'm looking at the kind used in the strobascope applications. https://en.wikipedia.org/wiki/Stroboscope

    I've created art using this concept and tried various strobes. The conventual novelty units work best, cell phone stobe apps do not. They seem to blur the visuals the conventual are crisp.

    Can you tell me why and also point me in the direction of concept to make a working circuit with sharper transient response?

    Thanks!

    • Did you try a simple PWM IC 555 based stroboscope circuit? or you can also try a NAND gate PWM circuit for generating absolutely sharp turn ON/OFF strobe effects

  13. Hey i tried 1st one and works perfect on 9v battery and if i connect them in my bike the bc547 gets heated and no blinking in bulbs..

  14. Thanks and it worked great..how to make them to blink twice one and twice other if we connecting them on other arm as you said above in comment?

    • For blinking it twice on each channel you may have to build another identical circuit, but without the collector resistors.

      connect the collectors at the junction of the respective resistor and LED of the on each channel of the previous circuit.

      adjust the new circuit to blink faster so that two blinks are injected on the LeDs.

    • …make sure the resistor of the LED is connected with the positive and the LED with the collector for implementing the above integration.

      if you have the LED connected to positive and resistor to the collector, just swap the positions.

    • led strips rated to work on 12V can be connected with the above circuit, change the transistors and check again, it seems the transistors are blown, replace them with 2N2222 or 8050

    • Yeah u r ryt it blown out…now works perfect as per ur diagram but brightness is low wt to do for it?i hv replaced two led and 680ohms into led strip..whats advantage of 2n2222 and 8050?how to check blown transistor? Btwn thnkz a lot finally my bike blinking:-)

    • LED strips already have internal resistors so may be R1, R4 can be eliminated from the circuit.

      2N2222 or 8050 are have higher current rating will not become warm or get damaged with higher current or voltages.

    • …..2N2222 or 8050 have higher current rating therefore will not become warm or get damaged with higher current or voltages.

    • R1too it won't affect ics?btwn does it is reduce the brightness of the led due to less current? I already removed r4.. Does it works on 24v circuit too? Thnkz for the kind reply 🙂

    • sorry No, if you are using only the R4 channel then you should NOT remove R1 otherwise T1 will blow off.

      yes you can 24V also but only if the strips are also rated at 24V

  15. Hi, the third circuit would perfectly suit your need. LS1 may be replaced with the LED,
    T4 = 2N2907
    T3 = TIP32
    R6 = 0.6/0.5 = 1.2 ohm it's the current limit for limiting the current to 500mA
    rest everything would be as per the given parts list.

  16. I'm an amateur with dc electrical circuits but quite fascinated and eager to try. I have been throwing around the idea of trying to build an electric fence charger. I think your strobe circuit would work. Would you agree? I need a constant on/off/on/off power source capable of delivering a high voltage shock while still not being strong enough to deliver permanent damage. These are the specs on a 2 mile fence charger.

    Item Specifications:
    115 volt, 60 cycle
    AC input/output
    0.5 joule output
    Pulsed output
    Output voltage no load is 2300 volts
    2 mile range

    I would like to build a tiny fence charger that would energize only about 50 ft. What do you think…is it possible?

  17. I got a few questions for you. I am a volunteer fireman and I'm thinking about using your design here for some emergency lighting for my jeep. How could i wire in 2 strips of LEDs both containing 6 LEDs, and make them alternate? Also can this circuit work on a 12v DC circuit?
    If you can email me about this I'm very interested in learning more.

    • The above circuit will work with 12V supply.

      You can use the first circuit with the following mods:

      Connect LED on the other arm also but use three LED in the series.

      You can accommodate another series of 3 on each arm with separate individual series resistors as done with the previous series, in this way you have six LEDs on each side.

      If you have readymade strips with the above series built in, you can simply connect each strip directly between the collector and the positive of the transistor on each arm..R1 and R4 will not be required in that case.

      he parts list would be:

      R1, R4(for the first option) = 150 ohms
      R2, R3 = 68K (the VR1/2 are not required, you can remove them and connect R2 R3 directly with the positive rail)
      Capacitors = 10uF/25V

      Transistors = BC547

    • Hi, I followed your first circuit diagram on a breadboard and it worked perfectly. I'm truing to make a 12v circuit using 12 festoon LEDs with inbuilt resistors. I can't quite work out from your written description what to do. Can you draw it?

    • Hi, if the LEDs are rated to work with 12V, you may connect 6 of them in parallel across each transistor collector arm, they should work, but the transistor may need an upgradation and may be replaced with 8050

    • Hi Swagtam, OK, getting closer. My previous post probably didn't accurately describe what I'm trying to do. I have a vehicle 12v festoon LED bulb that I want to rapidly blink. I originally didn't understand what you meant by connecting between collector and positive (I thought you meant the positive base of the transistor, and blew it up) but understand now that you meant the positive rail at the top of the circuit.

      OK, so I have removed R1 and R4. R2 and R3 are still the original 10k ohm resistor and the trim pots are still there at 100k ohm. I wired in the 12v LEDs where the original 3v LEDs are in the 1st circuit. Now I get the LEDs to light up, and dim slightly with a tweak of on of the trim pots, but no blink.

      Should I take out R2 and R3? Should they be replaced with a smaller ohm resistor? One last piece of info is that the 12v festoon LEDs measure 88.7 ohms across.

      Any help would be appreciated.

      Adam

    • Adam, yes making R2/R3 smaller will produce faster blinking rates so you can try replacing them with 1k resistors.

      If the LEDs are not completely shutting off, the reason could be leaky caps or wrongly connected cap polarity.

      If the caps are OK, you may try adding a series 50 ohm resistor with the LEDs to eliminate the issue or put 1N4007 diodes in series with the emitters of T1/T2

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