Hi ive got a bit further on my project but ive just noticed a problem when wiring the motor to the relay outputs on my plc . It works until i ad the reverse wiring which shorts the battery .
I know its basic electronics but does anyone know a solution using just theplc relay outputs ?
1. Unless it is a very small motor it is not a good idea to hook its power leads directly to the PLC relay outputs.
2. Assuming you still want to hook directly to the PLC outputs you will need to use a second bank of relay outputs which have a common which is isolated from the common of the first bank.
Bank 1
Common - Power Minus
Output 1 - Motor '-'
Output 2 - Motor '+'
Bank 2
Common - Power Plus
Output 1 - Motor '+'
Output 2 - Motor '-'
Forward - Bank 1 - Output 1, Bank 2 - Output 1
Reverse - Bank 1 - Output 2, Bank 2 - Output 2
IMPORTANT #1
Be absolutely sure to provide internal logic to prevent both outputs (1 and 2) on any bank from being on at the same time.
IMPORTANT #2
If you have the motor turned on in one direction and wish to reverse you must:
1. Turn off the current direction
2. WAIT UNTIL THE MOTOR STOPS!!! - this may be by some type of movement sensor a merely a timer set to the time it takes the system to stop.
3. Turn in the opposite direction
If you only have the output bank you illustrated you will have to use external relays to perform the direction switch.
