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
Stripboard Layout (approx. size: 55mm x 45mm) - copper tracks cut where marked with X
|BR1||Bridge Rectifier||W02M||Converts AC to DC.|
|C1 / C3 / C6||Capacitor||100nF|
|C2 / C4||Capacitor||100uF|
|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.|
|VR1||Voltage Regulator||7805||Converts input DC to 5vDC|
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.