Wiring a safety Warning alarm bell for a crane.


Senior Member
Retired EE
Hello, Okay, so, we have a 20 ton Overhead Bridge crane that has a Bridge, Trolley, Hoist. I am installing a remote control pendant but I will also need to add a warning light and an audible warning device when the bridge is traveling. I am not too familiar with relays but am wanting to get it in my skill set. I need the bell to only go off when you are either traveling (FWD) or (REV) In order to do that I am sure I need at least one relay in-line with the contactor (motor starter). For anyone unfamiliar, if I don't have a way to close the circuit from the direction not being used, it will back feed and most likely blow a fuse or an overload. If I had reversing contactors with a physical interlock, I could make that work, but I do not. This is a very old crane. Using Nema 1 -- 3 phase starters. The coil is 120v
Anyone who can draw me a schematic gets a cookie. :D I have looked around other websites and can't find a forum with Overhead Crane installation or maintenance experience. Thank you.... Logan



Based on your criteria that says:

1. Pendant remote control
2. Warning light with optional audible alarm
3. Use one relay
4.Safety interlock (electrical not mechanical)
5. Alarm only when bridge is moving in either direction.

Above is an schematic diagram without control relay.


The schematic diagram differs from your pictorial style diagram. . . which I'm sure you are familiar with.
It is more of an engineering oriented but as skilled as you are . . . .you shouldn't have any problem.
You can accomplish the same functionality with a single relay-- that I didn’t include here. Industrial components for the push button contacts are available from Allen-Bradley.

Use caution when deploying on actual machine. I recommend trying the completed assembly on the bench first. The scheme is based on accepted engineering practices. I'm not familiar with your technical skill so, I can only assume you can do it.
Things of this nature could result in property damage or injury-- even death if not done properly.

Good luck