Hi Guys,
I hope someone here can help me. I made up a time delay (RC) circuit which switches a relay via a pass transistor like this:
It works fine and gives me about 1.3 seconds of delay before the capacitor is charged enough to meet the minimum contact voltage of the relay.
Now, the thing I need some help with is this:
The voltage being passed to the relay coil increases over time. It starts at 0V, then climbs to the point where the relay contacts will close, then it will continue climbing up to nearly 12V. When the relay engages initially at the lower voltage, it sounds like it isn't engaging well. What I mean is: If I put connect the same relay directly to the 12V line it gives a very solid click. With the time delay circuit it is a much softer sound.
I want to use this relay in an application where some heavy current may flow through it, so I need a good solid connection when it engages. I have been thinking about a way to make the pass transistor activate only once the voltage reaches some pre-defined minimum like 10V or something along those lines, but have thus far not been able to get that working. I am certain the solution will contain a zener diode, but for the life of me I can not figure out how.
Please help me if you have any ideas around how to do that? If possible I prefer to use discrete components - not some fancy chips or things for this. Additional transistor, caps, resistors, zeners, etc are all fine.
Kind Regards,
Ian.
I hope someone here can help me. I made up a time delay (RC) circuit which switches a relay via a pass transistor like this:
It works fine and gives me about 1.3 seconds of delay before the capacitor is charged enough to meet the minimum contact voltage of the relay.
Now, the thing I need some help with is this:
The voltage being passed to the relay coil increases over time. It starts at 0V, then climbs to the point where the relay contacts will close, then it will continue climbing up to nearly 12V. When the relay engages initially at the lower voltage, it sounds like it isn't engaging well. What I mean is: If I put connect the same relay directly to the 12V line it gives a very solid click. With the time delay circuit it is a much softer sound.
I want to use this relay in an application where some heavy current may flow through it, so I need a good solid connection when it engages. I have been thinking about a way to make the pass transistor activate only once the voltage reaches some pre-defined minimum like 10V or something along those lines, but have thus far not been able to get that working. I am certain the solution will contain a zener diode, but for the life of me I can not figure out how.
Please help me if you have any ideas around how to do that? If possible I prefer to use discrete components - not some fancy chips or things for this. Additional transistor, caps, resistors, zeners, etc are all fine.
Kind Regards,
Ian.
