Hi, I am wondering how can I correctly realize this small demo circuit for school using mosfets in place of switches [1..3].
I came up with this: I would lights some LED using main power and, when main power goes off, the battery should take over and keep lights on. When main power is restored I keep the lights on and I can also charge the battery without extra devices (fixed ON state for sw1, playing with PWM on sw1 and LEDs are PWM-dimmed too by sw3, no resistors for them).
Easy to say, straight to think.. less to realize. I'm focusing at the moment on the switches implementation (assumption: I'm not worried at all by programming the logic inside a PIC, I can read currents flowing along the three wires (uhm, insulated inductive sensor), and I can read voltages at the three main devices, PIC's power and (hypotetical) driver power is assured anyway) :
_ if I would use N-type mosfets, I could use a generic driver, (like ir2101 and similar), then I should generate somewhere 9+10[V] to power the gates to turn them ON/OFF (signals will be PWM like, I want to control CURRENTS, not just opening paths). But I need to generated this kind of voltage.
_ with N-type again, I could move the mosfets putting their source leg to ground, so they would became easyer to drive, but (from my feelings) I don't like cutting ground connection here and there..
Do you have any suggestions? example and direction on how to think about it? I cannot find a lot of explanation on how to dispose and drive mosfets without the look and feel of "black" magic art..
Thanks!
[absurdity]If I would use relays in place of the 3 switches, and directly control them..but they won't keep up with the PWM! [/absurdity]
I came up with this: I would lights some LED using main power and, when main power goes off, the battery should take over and keep lights on. When main power is restored I keep the lights on and I can also charge the battery without extra devices (fixed ON state for sw1, playing with PWM on sw1 and LEDs are PWM-dimmed too by sw3, no resistors for them).
Easy to say, straight to think.. less to realize. I'm focusing at the moment on the switches implementation (assumption: I'm not worried at all by programming the logic inside a PIC, I can read currents flowing along the three wires (uhm, insulated inductive sensor), and I can read voltages at the three main devices, PIC's power and (hypotetical) driver power is assured anyway) :
_ if I would use N-type mosfets, I could use a generic driver, (like ir2101 and similar), then I should generate somewhere 9+10[V] to power the gates to turn them ON/OFF (signals will be PWM like, I want to control CURRENTS, not just opening paths). But I need to generated this kind of voltage.
_ with N-type again, I could move the mosfets putting their source leg to ground, so they would became easyer to drive, but (from my feelings) I don't like cutting ground connection here and there..
Do you have any suggestions? example and direction on how to think about it? I cannot find a lot of explanation on how to dispose and drive mosfets without the look and feel of "black" magic art..
Thanks!
[absurdity]If I would use relays in place of the 3 switches, and directly control them..but they won't keep up with the PWM! [/absurdity]
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