A simple TTL modulated diode laser

Posted on Feb 5, 2014

Measuring distances using a modulated laser. The circuit I created (see above) is very simple and does not need many explanations. The first part consists of a fixed voltage regulator 7805 to derive a stable +5 V source. This is followed by a LM317 adjustable voltage regulator since the diode laser module I found in my spare parts requires exactly 3 V -

A simple TTL modulated diode laser
Click here to download the full size of the above Circuit.

everything above this will kill the module immediately. Since I want to be able to modulate the laser beam by a TTL input signal, the circuit contains a 7607 non-inverting open collector driver IC which controls the laser module. The TTL input stage has a simple diode to protect the 7407 if a positive input voltage larger than +5 V is applied to the input jack. The picture on the right shows the front plate of the completed device. In the middle the laser diode module is visible which I glued into the metal enclosure by epoxyd glue. This was necessary since the frame of the diode module is at +3 V potential while the outer metal enclosure is at ground potential, so it is necessary to insulate the diode module from the frame. On the left the laser diode module can be seen which was originally part of a cheap laser pointer. The blue wire is ground while the yellow wire is +3 V. To the right of the module the 7407 driver can be seen. The picture on the right shows the component side of the circuit board I built. On the far right the 7805 voltage regulator can be seen while the LM317 is located left to the yellow ten turn potentiometer which is used to adjust the +3 V supply. The driver circuit 7407 is on the far left. The rear side of the completed device can be seen in the picture on the right. The four pole connector on the lower left side is the power connector - the BNC connector on the upper left is the TTL input for the...

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