Page 181 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists
P. 181
Chapter 6 Options for Creating and Controlling Motion 159
FIGURE 6-25 A transistor
current to flow from collector to emitter. We need a transistor here because even
though we can send timing signals to the motor directly from the 555 timer chip, we
can’t actually send the motor power through it. That would fry the chip (the chip can
handle only up to 200mA, and most motors use more than that). So we use the
transistor like an electronic switch to allow power to flow to our motor only when the
555 timer says it’s okay.
Shopping List:
• DC toy motor with wire leads
• Corresponding battery (9V used here) and snap or holder with wire leads (like
RadioShack 270-324)
• Breadboard (like All Electronics PB-400)
• Jumper wires (like SparkFun PRT-00124) or hook-up wire to make your own
(see Project 6-4)
• On-off-on toggle switch (like SparkFun COM-09609) or other SPDT switch
• Four AA batteries and holder (like SparkFun PRT-00552)
• 555 timer chip (SparkFun COM-09273)
• TIP120 Darlington transistor (Digi-Key TIP120-ND or Jameco 32993)
