i need help figuring our the values for the resistors and capacitor in this circuit.
It's easier if I just reproduce the question here:
A white LED lamp (L) operates at 2.4 V, 10 mA. Its energy is supplied from a capacitor, C. The lamp should operate for at least 30 minutes before needing to be recharged. To charge the lamp, it is connected to a 5 V supply through resistor R1 and terminals aa. When the lamp is docked to be charged, the switch is automatically flipped to the left position (disconnecting the lamp) and it is restored to the right side when the lamp is undocked. Charging should take less than 30 s (now you see why it uses a capacitor, not a battery). What values of R1, R2 and C would you recommend.
I think I have figured out R2 by subtracting 2.4 V from 5 V to get 2.6 V and then using the LED current to figure out the resistance. I got 260 Ohms. Does that sound right? I'm not sure how to proceed on to the next step. Do I need to figure out a time step for the capacitor?
Thank you for any help with this.
It's easier if I just reproduce the question here:
A white LED lamp (L) operates at 2.4 V, 10 mA. Its energy is supplied from a capacitor, C. The lamp should operate for at least 30 minutes before needing to be recharged. To charge the lamp, it is connected to a 5 V supply through resistor R1 and terminals aa. When the lamp is docked to be charged, the switch is automatically flipped to the left position (disconnecting the lamp) and it is restored to the right side when the lamp is undocked. Charging should take less than 30 s (now you see why it uses a capacitor, not a battery). What values of R1, R2 and C would you recommend.
I think I have figured out R2 by subtracting 2.4 V from 5 V to get 2.6 V and then using the LED current to figure out the resistance. I got 260 Ohms. Does that sound right? I'm not sure how to proceed on to the next step. Do I need to figure out a time step for the capacitor?
Thank you for any help with this.
Attachments
-
7.1 KB Views: 112