Shopping List: Experiments 6 Through 11
42 Chapter 2
Components
Pushbutton
Momentary-on, SPST, sometimes referred to as OFF-(ON) or (ON)-OFF
type. Must be PCB- or PC-mount, meaning is extremely small with thin
spiky contacts on the bottom. Quantity: 1. See Figure 2-11.
Examples are part number AB11AP by NKK, part MPA103B04 by Alco-
switch, or part EP11SD1CBE by C&K. If you have a choice, buy the cheap-
est, as we’re going to switch very low current.
Switches
Toggle switch, single-pole, double-throw (SPDT), sometimes referred to
as ON-ON type. Quantity: 2. See Figure 2-12.
Model S302T-RO by NKK is ideal; it has screw terminals that will eliminate
the need for alligator clips. Other options are catalog item MTS-4PC from
All Electronics or part 275-603 from RadioShack.
We won’t be switching large currents or high voltages, so the exact type of
switch is unimportant. However, the terminals on larger-size switches are
spaced wider apart, which makes them easier to deal with.
Relays
DPDT, nonlatching, 12v DC. Quantity: 2.
It’s important to get the right kind of relay—one whose configuration
matches the pictures I’ll be using. Look for parts FTR-F1CA012V or FTR-
F1CD012V by Fujitsu, G2RL-24-DC12 by Omron, or OMI-SH-212D by Tyco.
Avoid substitutions.
Potentiometer
1 megohm linear potentiometer, Part number 271-211 from RadioShack,
part number 24N-1M-15R-R from Jameco, or similar.
Transistors
NPN transistor, general-purpose, such as 2N2222 by STMicroelectronics,
part PN2222 by Fairchild, or part 2N2222 from RadioShack. Quantity: 4.
See Figure 2-13.
2N6027 programmable unijunction transistor manufactured by On Semi-
conductor or Motorola. Quantity: 4.
Capacitors
Electrolytic capacitors, assorted. Must be rated for a minimum of 25 volts
and include at least one capacitor of 1,000 μF (microfarads). If you search
on eBay, make sure you find electrolytic capacitors. If they’re rated for
higher voltages, that’s OK, although they will be physically larger than you
need. See Figure 2-14.Figure 2-11. The terminals protruding from
this tiny pushbutton are spaced 0.2 inches
apart, making it ideal for the “breadboard”
that you’ll be using.
Figure 2-12. This relatively large toggle
switch made by NKK has screw terminals,
which will reduce the inconvenience of
attaching it to hookup wire.
Figure 2-13. Transistors are commonly sold
either in little metal cans or sealed into
little lumps of plastic. For our purposes,
the packaging makes no difference.
Figure 2-14. An assortment of electrolytic
capacitors.