cyclic timer

[alexander]

Now I'm planning to do automated feeder for the fish. i'm using cyclic timer to control the time. how am i going to control the mechanical gear with the circuit? 1 more thing, there's transformer on the circuit, what is the function of the transformer? how am i going to use it? ???

[ante]

Alexander,
Welcome to this forum.

It

[Kevin Weddle]

Are you going to use the motor to control a valve? The motor can be caused to turn slightly by applying a small voltage. You want the small voltage to change polarity so I would use a two polarity supply. The logic will will supply a high or low when you need the motor to turn. It will have one output to control one direction and the other ouput to control the other direction. So you will have the motor turning one direction and then the other. Now you have to apply the voltage. Use an NPN in series with the motor with the collector to the voltage source. Use a PNP in the same manner so that it is in parallel. Now you need to feed the base with each input. Use a special circuit called a pushpull amplifier. This amplifier will take the logic and deliver the correct voltage. A push pull is constructed using two NPN's with a phase splitter transistor. Bias it to give you 0volts on the ouput. When you apply the logic through a resistor you will come up with the required voltage. So then you should have your motor turning one direction an then the other. The time will be short but it will occur at the time your logic dictates.

I don't want to retype this but the idea is the same. You can use your pushpull amplifier to deliver to the motor. You don't even need the NPN and the PNP. Just drive the pushpull with the logic to the motor. The only thing missing is the time span. You want to turn the motor in one direction and then the other. The logic will dictate what time this occurs, but not the duration. So you need the logic to deliver the duration. This can be done easily. The output from the logic circuit will be a high or low at the given time. You need tristate capabilty to keep the motor from turning when you don't want it to. Your logic output will need to go high and then low to send the motor in both directions. This can be accomplished using logic feedback. In other words you will have it go high at a particular time, the motor will go in one direction, and the the high will go low sending it in the opposite direction. Then you are done. Just remember that there exists this time when the motor must go out and pull back. This is the short duration that the logic will have to provide.