Download Electronic Component Ordering R32C Web Server

adequate for a micromotor), a 7805 voltage
regulator generates a stable 5-V operating
voltage. This voltage is used to power the
other ICs in the circuit. A second voltage
regulator (an LM317) is used to reduce the
voltage to 1.5 V, since the windings of the
micromotor require a relatively low operating voltage.
The frequency of the three-phase drive signal is controlled by a 555 configured as a
square-wave generator whose output frequency can be adjusted by a potentiometer
over the range of 60 to 600 Hz. This signal
is fed to the clock input of a CD4018 presettable divide-by-N counter. The Q1, Q3 and
Q5 outputs of this counter drive the motor
windings via a set of BC517 Darlington transistors with 33-Ω series resistors to limit the
motor drive current. The CD4018 is configured to operate as a divide-by-six counter
by connecting pin 6 to pin 1. The signals on
the Q1, Q3 and Q5 outputs drive each of the
windings in sequence with a certain amount
of overlap, which creates a well-defined
rotating magnetic field in the motor.
Figure 10. Schematic diagram of a micromotor drive circuit.
With suitable modifications to a few component values,
this circuit can also be used to drive larger motors with three windings.
shown in Figure 4. The rotor consists of a
very small magnet (5) that is eroded and
ground to the right dimensions and has a
hole for the attachment of the shaft (6). Two
tiny plates with cutouts (7) act as the upper
and lower portions of the motor housing.
Figures 8 and 9 show the complete assembly. The winding are glued in place between
the upper and lower plates, so they effec-
tively form the rest of the housing.
If you want to experiment with your own
DIY motor, you can use the schematic diagram shown in Figure 10. This is the original circuit that Jos used to drive his micromotor. The design is simple but very effective. Starting from a 9-V supply voltage
(provided by several penlight cells in a battery holder or a single 9-V battery, which is
If you want to use this circuit for your own
projects, you can modify the frequency and
voltage of the winding drive as necessary.
Bear in mind that the BC517 transistors have
a maximum rated peak current of 1 A, so a
larger type must be used if higher currents
are necessary.
(090499-I)
Advertisement
Prototype & small series PCB specialists
ice
serv
e
p
y
t
proto
PCB
w
e
N
Instant online pricing and ordering
Low order-pooling prices - 1–8 layers
Full options service On demand - 1-16 layers
Deliveries from 2 days
Stencil service
Call us: 020 8816 7005 Email: [email protected]
www.eurocircuits.com
62
- 2 boards in 2, 3 or 5 days
- No tooling charge
- Low PCB-Proto prices
E.g. 2 x 100 x 80 mm: 2 layers 38.12€ each*
4 layers 77.23€ each*
- Immediate online ordering
- No minimum order charge
*excluding transport and VAT
11-2009
elektor