Monday, April 06, 2015

Enable Relay

Today I glued up the top of one of the tanks.  Then while the glue set I worked on designing the relay wiring for the SBT enable.

 I found the paperwork for it, a Square D 8501 RSD4 P14  the D means DC   RS is Relay Switch  P14 is the indicator LED and the 4... I guess because it has 4 contacts?
 After studying the paperwork, the emails from Robb, and this website http://www.how-to-wire-it.com/how-to-wire-a-relay.html  I drew up the power wiring diagram.  The thick red lines are the high amp power wiring.  The thin black lines are lower amp enable wiring.  In the first case the machine is completely off, the master power is open.
 First we close the master power, but nothing will happen, the enable needs to see 24V also.
 Because the board is funny and 0 voltage is full throttle (not shown) we need a push button test of enable to make sure the machine will not run away.  If it does run the finger will fall off the push button and it will open and machine will stop, then we can fix the problem, usually the radio control did not sync, and try again.
 After a successful test enable we can push the button for full enable, this energizes the relay coil and switches the 4 switches.  Only two of the switches are used here, free parts...
 Then we let go of the start push button and because the 9-5 contact of the relay is now feeding the coil the 12-8 switch stays closed and enable is activated.
At least until the fuse goes, the master power is cut, or I press the stop button.

And there we have it.  Physically the 4 switches and the fuse is tucked under the side of the SBT.  Easiest to reach is the master power, then next is the test, and tucked behind the test is the start.  The stop button is an emergency button on top of the machine.

No comments: