I wish to operate a 5 volt DPDT relay with a 555 timer. Based on suggestions on the internet, I figured that the output of the 555 timer is connected to one pin of the coil of the DPDT relay through a diode and the other pin of the relay coil goes to ground. Is this correct?
But when I am physically connecting the output of the timer to the relay (whether through a diode or not), something strange happens. The relay switches on as soon as the output of the timer goes high but after that it remains switched on and the output of the timer also remains constantly high. I have checked the relay and the timer separately and they both seem to work fine. The timer produces the output pulse (goes high and low) at specific intervals as expected when not connected to the relay... I am even able to drive a flashing LED setup with it, but when I connect the output of the timer to the relay it doesn't work as expected.
The relay is a non-latching DPDT type, connecting and disconnecting the coil pins directly to the power rail causes it to close and open as expected.... its only when I am connecting it to the output of the timer it behaves this way.
I am using a 9V power supply. The voltage at the end of the diode as it reaches the coil becomes constantly +6.5 V when connected to the relay and shifts between +16V and +4.5V when not connected to the relay. The timer output when the diode and relay are disconnected is a constant pulse of +7.6V and 0V. The timer is running in astable mode with the time interval of 4 seconds with 50% duty cycle.
What am I doing wrong? Can someone please help me figure this out?
But when I am physically connecting the output of the timer to the relay (whether through a diode or not), something strange happens. The relay switches on as soon as the output of the timer goes high but after that it remains switched on and the output of the timer also remains constantly high. I have checked the relay and the timer separately and they both seem to work fine. The timer produces the output pulse (goes high and low) at specific intervals as expected when not connected to the relay... I am even able to drive a flashing LED setup with it, but when I connect the output of the timer to the relay it doesn't work as expected.
The relay is a non-latching DPDT type, connecting and disconnecting the coil pins directly to the power rail causes it to close and open as expected.... its only when I am connecting it to the output of the timer it behaves this way.
I am using a 9V power supply. The voltage at the end of the diode as it reaches the coil becomes constantly +6.5 V when connected to the relay and shifts between +16V and +4.5V when not connected to the relay. The timer output when the diode and relay are disconnected is a constant pulse of +7.6V and 0V. The timer is running in astable mode with the time interval of 4 seconds with 50% duty cycle.
What am I doing wrong? Can someone please help me figure this out?
Last edited: