A toy's small DC motor can be used to mount a liquids shaker. The shaker
can be used in chemical experiments to mix substances quickly and efficiently.
The circuit is powered from the power supply line (to avoid the expense of
batteries), but there is no shock hazard because an isolation transformer is
used. Of course, for fieldwork you can also power your mixer from common
AA cells.
The transformer is chosen according to the motor voltage. A four-AA-cell DC
motor requires a 6+6 volt x 500 mA transformer (a 6-volt center tapped transformer). A two-AA-cell DC motor requires a 3V x 500 mA transformer.
Secure the motor into a small cylindrical plastic box. Use a long shaft to attach a small plastic screw propeller.
Figure l shows the schematic diagram of the electronic part of the circuit: a
power supply. The diodes are common 50V x 1A silicon rectifiers, and C1 is
not critical. C1 should be in the range between 100 and 1,000 uF.
Figure 2 shows a mechanical view, using a small terminal strip as chassis.
The fuse is important to avoid severe troubles if shorts occur.
Rl is a current-limiting resistor and can be altered according to the motor.
Vafues between 4.7 and 100 ohms can be experimented with for better performance.
Position of the polarized parts, such as the diodes and electrolytic capacitor,
should be observed. Remember that the motor rotates clockwise or not according to the voltage polarization.
Parts List - Liquids Shaker
D1,2 - 1N4002 silicon diodes
T1 - Transformer: 1 17 VAC: 6+6V x 500 mA - see text
S1 - SPST slide or toggle switch
F1 - 500 mA fuse
C1 - 220 uF, 16 WVDC electrolyticapacitor
R1 - 15 ohm, 2W,SYo resistor
M - small DC motor (3 to 6 volt)
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