I have a fan in my house, It has an electronic PCB that responds to a remote control. The PCB has a voltage dropping capacitor so, I think it is supplied with a very low voltage such as 9 or 12 volts. There is no relays on the PCB nor inside the fan, How can the PCB control the 220 volts AC induction motor ?
How to control 220 volts without using relays
controlcontrol systemfanpower supplyrelay
Related Solutions
Your Arduino output ports can't supply the kind of current needed by your motors. Worse, they are not prepared to take the inductive spikes that can be caused by brushed DC motors.
The solution to both problems is to use either a relay, or an H-bridge (with kickback diodes). Unfortuantely most H-bridges are not optimized for 6V, most prefer 12V or higher. For low currents you might check an LD293D, although it won't do that well at 6V.
If you use a relay note that you can't connect a relay directly to the Arduino pins. There are plenty of relay boards for Arduino that combine a relay with a transistor and the kickback diode (which is now needed for the relay coil).
Note that it might not be a good idea to use the same power for both the motors and the Arduino. Start with two separate battery sets. If you get everything working you might try combining the batteries, maybe with some spike suppression. If anything goes wrong then you know the likely cause.
When we look at the internal circuit diagram of the relay it looks like the following:
I have also added one motor to show how the connections are to be made.
Vcc is the signal given by the microcontroller (one of the output pins from the Arduino). When this signal is given the SPDT switch changes state to NO. This completes the circuit and the motor will rotate.
Note Vcc is just a 5v signal if from the microcontroller (Assuming this is the rating of the relay). But Bat2 needs so supply the required voltage and current for the motor to run.
Now moving onto what you want to achieve in your project, the description is vague. You are running 2 pairs of motors with 4 Relays. I presume each pair is controlled by 2 switches. One for moving forward and one for moving backward. The same for the other pair.
The circuit diagram looks like the following:
Truth Table: U1 - M1 and M2 Forward
U2 - M1 and M2 Backward
U3 - M3 and M4 Forward
U4 - M3 and M4 Bakcward
U1 and U2 - Nothing
U3 and U4 - Nothing
All other combinations can be inferred as M3 and M4 are isolated from M1 and M2. You have to make sure your battery can handle running all 4 motors at once though.
Best Answer
A triac or alternistor is the normal way to control relatively high current AC (other than relays). Alternistors are similar to triacs, but behave better with inductive loads where regular triacs can fail to commutate (turn off). For example, the BTA12:
The triac can be used to switch windings (discrete speeds) or for phase control. Here is a Freescale app note showing a ceiling fan speed control design using phase control.
The transformer and opto-isolator shown are for safety reasons and could be omitted in a carefully designed and manufactured commercial product (to save money).