I found the following circuit at http://darrenyates.com.au/electronics/archives/44
My question is, how could I adapt this circuit to run at 34VDC? (More details below the image.)
The circuit needs to work with 34VDC because the power is supplied by a 24VAC transformer converted by a single diode and a 330uF capacitor. The circuit is needed to provide a short delay, maybe 1 second, before activating a 24VDC relay, then stay active until the power is cut. (The circuit should rarely activate, but I'm still a little concerned about 34V at the 24V relay coil. The good news is, it hasn't died yet!)
Right now I have a different system set up, using a buck converter and an ATTiny85 microcontroller controlling the relay. The point of trying to use the transistor delay circuit is to keep things a little more simple and inexpensive. Ultimately I will need to make this circuit 52 times.
One of my first thoughts is to use an 18V zener diode so the capacitor might only need to charge to less than 60% before activating Q1. The timing will also need to be adjustable. I'm guessing that adding a variable resistor before C1 would do it.
Any ideas would be interesting to me.
My question is, how could I adapt this circuit to run at 34VDC? (More details below the image.)
The circuit needs to work with 34VDC because the power is supplied by a 24VAC transformer converted by a single diode and a 330uF capacitor. The circuit is needed to provide a short delay, maybe 1 second, before activating a 24VDC relay, then stay active until the power is cut. (The circuit should rarely activate, but I'm still a little concerned about 34V at the 24V relay coil. The good news is, it hasn't died yet!)
Right now I have a different system set up, using a buck converter and an ATTiny85 microcontroller controlling the relay. The point of trying to use the transistor delay circuit is to keep things a little more simple and inexpensive. Ultimately I will need to make this circuit 52 times.
One of my first thoughts is to use an 18V zener diode so the capacitor might only need to charge to less than 60% before activating Q1. The timing will also need to be adjustable. I'm guessing that adding a variable resistor before C1 would do it.
Any ideas would be interesting to me.