Simple Light Switch





Introduction: Simple Light Switch

In building Simple Bots, we are going to use a series of photo-coupled devices called modules. But, before we can do this, we need a good photo-couple to use as a light-activated switch. To make one of these switches, we will be using a special OSRAM-brand photo transistor and any standard NPN transistor (like a 2N2222, 2N3904, BC546, etc.). These switches will allow the motor to spin in direct correlatoin to how much light it senses. In other words, the more light, the faster the motor goes and the less light, the slower.

Step 1: Go Get Stuff

You will need:

(x1) OSRAM-brand photo transistor
(x1) NPN transistor

Step 2: Line Up

Lay the phototransistor atop the NPN transistor such that the base of the NPN transistor aligns with the emitter (longer leg) of the phototransistor and the collector of the NPN transistor aligns with the collector of the phototransistor.

Step 3: Twist

Twist together each lined-up pair of NPN transistor and phototransistor leads.

Step 4: Solder

Solder together the connections of each twisted pair of transistor leads.

Step 5: Trim

Trim the middle pair of wires such that it is shorter, but the connection between the base of the NPN transistor and the emitter of the phototransistor remain soldered together.



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    will this work to power leds?

    I would guess it should. Not 100% sure though.

    Any other substituent for osram based phototransistor? Thanks

    it is so helpful to me!!!
    now i know more on sensors

    Wow. I hate to see what this would look like if I did this. SOLDER BLOBS IN MEH EYES!

    very clean. while I like circuit boards for organization, free-form circuitry is always really cool when you can pull it off.

    If I make this light switch, which lead would I attach to the load and which would I attach to the power?

    Randy, this is very interesting, but lacks some explanations for those as me, that are almost absolutely ignorant in electronics. Please add a circuit of how it is connected to activate a motor.

    How many volts can it handle? How many watts?

    When I redo my solar cooker, this can be a very simple device to keep it aligned with the sun. The cooker will have equatorial mount, so with only one movement, only one motor, it will be aligned.  That can be done easily putting your light switch into a black tube, or behind a black screen for when clouds hide the sun for a while.

    Don't expect too much current handling for to92 packages. The most usual are 100-200mA (to92 with metallic can reach 800mA). Voltages are variable, usually around 40V in C-E.
    But they are hard to be cooled and these parameters usually are the maximum.

    More flexibility can be achieve with the to220 packages, usually TIP series, for example... there're many different types of transistors for resuming here xD

    Thanks for the data, gomibakou. I want use it to feed a 12V motor with reductor, those used in car glass lifts. I think the intake is not so high.

    Do you suggest to replace the Phototransistor? Forgive my ignorance.