I'm making an irrigation control system with 24VAC valves, 12vDC relays and 9vDC Arduino controller.
When I cut the 24vAC "in half" with a single power diode and smooth with a capacitor I read 40vDC.
I've bought a series of voltage regulators hoping to cascade down the voltage (all TO220)
MC7824CT (24v out, 40v max input)
LM10851T-12 (12v, 3A out, datasheet says 18v max input
LM7809
Both the 24v and 12v regulators get hot to touch when running with no load. (EDIT correction - it is drawing 80mA when driving Arduino with 9v)
I could add heat sinks.
But would the 24v regulator perform OK if I omitted the capacitor, i.e. used un-smoothed half wave input?
In any case this seems a clumsy setup (I thought I'd simply get 12v with the single diode). Perhaps I'm better to go to a separate power supply but that's clumsy in a different way.
Edit again... If it's "too hard" I'm tempted to replace the 24v transformer with a multi-tapped one to get the lower voltages.
When I cut the 24vAC "in half" with a single power diode and smooth with a capacitor I read 40vDC.
I've bought a series of voltage regulators hoping to cascade down the voltage (all TO220)
MC7824CT (24v out, 40v max input)
LM10851T-12 (12v, 3A out, datasheet says 18v max input
LM7809
Both the 24v and 12v regulators get hot to touch when running with no load. (EDIT correction - it is drawing 80mA when driving Arduino with 9v)
I could add heat sinks.
But would the 24v regulator perform OK if I omitted the capacitor, i.e. used un-smoothed half wave input?
In any case this seems a clumsy setup (I thought I'd simply get 12v with the single diode). Perhaps I'm better to go to a separate power supply but that's clumsy in a different way.
Edit again... If it's "too hard" I'm tempted to replace the 24v transformer with a multi-tapped one to get the lower voltages.
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