General Purpose Timer for Faller 16vAC Motor

Aim of Project:
To produce a General Purpose Timer for use with Faller's 16vAC motor.
The circuit board will use off-the-shelf components - no user-programmable chip will be needed.
The circuit will contain two potentiometers that can be adjusted to switch the motor "on" for up to 230 seconds (approx.) and an "off" for up to 70 seconds (approx.).


The Faller 16vAC motor


Flow Diagram


Stripboard Layout (approx. size: 55mm x 45mm) - copper tracks cut where marked with X

Shopping List:

Bridge Recifier: W02M
Capacitors: 3 x 100nF, 2 x 100uF, 1 x 220uF
Diodes: 2 x 1N4001
Potentiometers: 500k, 1M
Relay Switch: 5v SPDT
Resistor: 10k
Single-core wire: eg. 1/0.6mm
Stripboard: 23 x 17 (55mm x 45mm approx.)
Multi-core wire: eg. 10/0.1mm
Timer Chip: NE555 + 8-pin IC socket
Transistor: BC337
Voltage Regulator: 7805 1A

Key Component Value Notes
BR1 Bridge Rectifier W02M Converts AC to DC.
C1 / C3 / C6 Capacitor 100nF
C2 / C4 Capacitor 100uF
C5 Capacitor 220uF
D1 / D2 Diode 1N4001
J1 / J2 Input Power Connections 10/0.1 12v - 16v AC power from transformer
J3 / J4 Ouput Power Connections 10/0.1 12v - 16v AC power supply to AC motor.
K1 Relay 5v SPDT To control flow of AC to motor.
NE555 Generic Timer Chip NE555
P1 Potentiometer 500k To vary the "off" time period.
P2 Potentiometer 1M To vary the "on" time period.
R1 Resistor 10k
VR1 Voltage Regulator 7805 Converts input DC to 5vDC






Additional Notes:
1. The "on" period can be varied by using a small screwdriver to turn the dial on Potentiometer P2, the "off" period can be varied by adjusting Potentiometer P1. It should be noted however, that adjusting P1 also has a slight effect on the "on" period, so P1 should be set first before making adjustments to P2.
2. The "timing" works by charging and discharging the 220uF capacitor. During the discharge phase, the capacitor is not completely discharged before the charging phase begins again. The downside to this is that when power is first connected, it takes time to build up this residual charge - this results in the first "on" period being about 50% - 75% longer than subsequent "on" periods. To get consistent results, the first on/off cycle needs to be completed before attempting to adjust the Potentiometers.

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