@colin55
The circuit in post #15 will need adapting to get a 30 sec fade period. It currently gives a 3-4 sec period.
Re Ohm's law, take a look at the stated voltage at point X in the schematic and work things from there.
Google for n-channel mosfets.
I'm not recommending any particular manufacturer, but here's a page selected at random https://www.vishay.com/mosfets/n-channel/to-220-package/
Just pick one with Vds at least 30V and Rdson less than ~ 0.05.
If i searched right I don't think digikey has any with this rating Mouser has it but digikey arrives a little faster and with the recent storm that hit TX might slow it down some.
If i were to try this I'd use an LM317 or 338 with a voltage divider and an RC component on the reference leg of the regulator. So basically you'd get a slow ramp up and down on the voltage which will translate into brightening and dimming of the LEDs via a dropping resistor. No other IC's or transistor drives needed. You will need a DC supply of about 1.5V over the target max voltage though.
I've used a PWM technique into an RC filter on such a regulator b4 to create control of a linear voltage for batt. charging.
going to use the IRF510 for the mosfet but I was going over the design and with those bjt's it would lower the gate voltage on the mosfet too much so I was going to omit them in the circuit.
The transistors make a good gate driver because they supply enough current to quickly charge and discharge the high gate capacitance. Without the transistors the Mosfets will ramp instead of switch and will get very hot unless you reduce the switching frequency a lot.
Don't you have a 12V supply? Then the Mosfets will turn on fine with a gate voltage of +11.3V.
I have a question about the switch in the post #11 is that needed because I had not planned to use a switch on the circuit since it's going to be on a walloutlet that the supply 12V is going to come from which is controlled by a switch.
Also my stuff arrived today but does anyone have a pinout for the CD40106BE
I can find one for the CD40106B but what changes does the (E) version have?