Make: Volume 93

idea (learn more at makezine.com/go/laser-eye-

safety). Also be aware that powerful lasers may

be regulated by federal agencies. Search for

“laser regulations” to learn the details.

THE CIRCUIT

Now, how is this going to work? Check the block

diagram in Figure

G

.

First you set the number of pulses in your

message, using the rotary switch at far right,

then you press the Start button. Simple — but

the circuit must deliver the complete number of

pulses even if you let go of the button. Therefore

a latch sustains the high output, which enables

a pulse generator (a 7555 timer). It sends pulses

to the laser, and also to the clock input of a

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