Relay making a whining noise

i have a 250 ohm coil, .5 amp contact relay that im activating from a 555 timer in monostable mode. when not active, the realy made a high pitched whining noise, like a capacitor charging, only decreasing in pitch. after a while, the circuit stopped working. i tried replacing the timer. no luck.

thank you for any suggestions!

Do you Know if the Relay Contacts Are Chattering or is the Coil Humming?

i have no idea which it was

i would describe it as humming though

is there a way to tell?

The humming can be caused by a number of things.

1) Poor filtering on Power Supply.

2) Oscillation from Timer Circuit (also Called Ringing)

3) Poor Ground Connection

4) Negitive Pulse with a negitive Common lead on the Relay

5)Low Voltage from the output Pulse causing the Relay to Barely hold.

You may need to Run the relay with a Transistor to stop the Humming.
Check the voltage of the Timing Pulse.