Closing a circuit with a capacitor

[daniel_i_l]

I have an electromagnet that I want to be activated for two seconds as soon as I turn the power on. I think that this can be done by connecting the electromagnet to the power source in a series with a capacitor and a resistor. As soon as the power is turned on the EM would work until the capacitor gets charged up and cuts off the circuit. Is that true? If so, how do I calculate the sizes of the resistor and capacitor that I need?
Thanks.

 

[TurtleMeister]

I don't think the capacitor idea is a good solution to your problem because the current will gradually decrease as the capacitor charges. I'm assuming you would prefer to have the electromagnet have it's full power for the duration of the time interval. Also, you would need to have a safe way to discharge the capacitor after power is removed. A better solution would be to use a normally-closed, timed-open, relay.
http://www.allaboutcircuits.com/vol_4/chpt_5/3.html

 

[oswaler]

Yes, it is true that using a capacitor in series with the electromagnet and power source can create a timed activation for the electromagnet. This is because when the power is turned on, the capacitor will initially act as a short circuit, allowing current to flow through and activate the electromagnet. However, as the capacitor charges up, it will eventually reach its maximum capacity and act as an open circuit, cutting off the flow of current and deactivating the electromagnet.

To calculate the sizes of the resistor and capacitor needed for this circuit, you will need to consider the desired time duration of the electromagnet's activation, the voltage and current ratings of the power source, and the resistance of the electromagnet. Using the formula for the time constant of a RC circuit (T = RC), you can determine the appropriate values for the resistor and capacitor to achieve your desired time duration. It is also important to choose components that can handle the voltage and current levels of the circuit to ensure safe and reliable operation.

I would recommend consulting with an expert in electronics or using online calculators to determine the exact values for your specific circuit. Additionally, it is important to carefully test and adjust the circuit to ensure it is functioning as intended before implementing it in any practical application.