Yes, I missed that part, but it was still a bit over complicated.
I would use two comparators with open collector outputs, each would have different reference voltages and some hysteresis. The LED would have three series resistors at its ground connection, I would use the comparator outputs to short the appropriate resistor when it gets too dark, I canl draw to a diagram if you don't get me.
yes, that's a good one - basically my 3rd option, if you hadn't noticed. though I think hysteresis isn't necessary.
by the way, while it's kind of silly for a mower. some autos have tri-level instrument lighting based on ambient light. it's backwards from the intent here but it makes sense - bright lighting when it's bright, middle during "tween" times and dim when it's dark.
Silly it may be, but quite a bit of applications! LG TVs use this for ambient light controlled Brightness/contrast, with an enhanced cost, ofcourse.
Also in many instrument/annunciator display lamps to save battery power during day-light hrs.
"Silly" might mean " Whatever-for in a Lawn mower?!" kind of thing.
But this thread has helped many, as I can see.....for many other applications.
It's been used by a great many TV's over the years, the first I can recall were some Pye sets from the 1950's, but that's not to say they were the first?. However, it's always been a really useless feature - but it's very cheap to do!, and it's an extra gimmick - just make sure you can turn it off.
Yes, a photos resistor is the same thing as an LDR. (It's resistance lowers with increasing light levels, right?)
I think the circuit with the resistor, LDR, and LED use the least power just because it has less components(plus it also adjusts brightness automaticall). I also think the relay circuit only has on/off and no "middle" brightness level.
No, it's a wasteful 'circuit', because it uses MORE current when the LED is dark than when it's lit - it's also not likely to work very well, and not at all unless you can get a really low resistance LDR, most will be too high to work. There's not much to admire about it at all, except it's lack of components - which probably isn't a good thing?.
Well if the relay is closed, doesn't that create a straight path for current to flow down the right branch from +6V -> relay -> transistor ->GND. This would only happen if the gate voltage was pulled high, but since no current will flow through the right branch, I can't figure out whether or not the gate potential will be at GND or +6V to switch the transistor on to cause the short.
Well if the relay is closed, doesn't that create a straight path for current to flow down the right branch from +6V -> relay -> transistor ->GND. This would only happen if the gate voltage was pulled high, but since no current will flow through the right branch, I can't figure out whether or not the gate potential will be at GND or +6V to switch the transistor on to cause the short.
A relay isn't a short circuit, it's a solenoid that moves a mechanical switch, and the solenoid has resistance - which is listed in the specifications of the relay - some can be quite high. But no matter what it's resistance, it's designed to work at it's rated voltage - so why should placing the relay across it's intended supply cause a short?.