That might be difficult with a PM motor rewound/repurposed as a generator.You should be regulating the field or excitation rather than the output!!
Max.
That might be difficult with a PM motor rewound/repurposed as a generator.You should be regulating the field or excitation rather than the output!!
Max.
Not surprising. Unless the LEDs have closely matched forward voltage (Vf) characteristics, one will hog all the current. That's why it's generally bad practice to connect LEDs in parallel.If I add another LED in parallel, the second LED never lights up.
It can take up to 80 volts, but it works down to the LED drop (say 3 volts) plus 2 volts. So in your case 5 volts minimum. Then it holds the current steady at 20 ma even if the voltage increases. That's why it is called constant current.Thank you.
I looked at the link you gave for the controller, and it says voltage output is 80v. If my current is regulated, do I care what the voltage is?
I'd like to try some of these... here come the rookie questions: If I run 2 LEDs (maybe more) that need 20mA @ 3.2V, do I want a 20mA driver?
I am working with a wind-powered generator that only needs to light up some LEDs when the wind blows.
I rewound my generator to make enough voltage at low RPM, but as expected, it provides too much as the wind speed picks up.
I figured a voltage regulator would cure the problem, but I can't seem to get it to work. I get it dialed in at a certain shaft speed, but then as the speed rises, so does the output. I'm using a simple LM317 adjustable regulator.
Isn't the regulator supposed to supply a constant output regardless of input? What might I be overlooking?
It really doesn't. wallaby is powering LEDs. The input is the wind. At maximum input the loss is (40-6)*0.03 = 1W. That's 25°C above ambient. No big deal. More importantly, what were you going to do with the extra power you save? Spin the generator faster? Save on wind?This implies very poor efficiency at high speeds i.e. overheating.
wallaby, get it working with the linear regulator first. A switch mode is far more complex and unlikely to gain you anything.Your best option is to use switching mode regulator.
Petkan:I first thought parallel would be best in case one light failed. LEDs don't like this, I guess.
I am thinking of ditching the fancy blinking light controller. At a minimum, I would be happy with 2 LEDs that come on when the propeller turns at a reasonable speed.
The problem is that I need RED and GREEN lights... and the red always requires less power than the green.
I managed to find a pair of high-flux LEDs where the red and green colors have identical ratings. But they have 4 pins. They give a diagram showing the anode and cathode, but are there two of those, or the other two pins are dummy.
These LEDs (both red and green) take 3.2v and 20ma.
My generator makes 2.8v at 28 rpm
4.8v at 48 rpm, 7.7v @ 77rpm, etc . So I have enough to light up the LEDs when it's spinning at the speed of a record turntable. As I add regulators, it takes nearly double the speed to get the lights to come on.
I am just trying to find the least power-robbing way to keep the LEDs happy.
Assuming firstly there's no current regulator, use a potentiometer in your voltage regulator feedback circuit so you can adjust the output voltage. Start at about 4V to be safe, and increase from there while monitoring current. Do not exceed 20mA. In fact, don't go above about 15mA to allow for variation over temperature, component tolerance and voltage sharing. Will probably be about 6V, but beware that it will be far from linear - a small voltage change can cause a big current change. To improve voltage sharing between the LEDs, you could add a parallel resistor of say 1K to each one but it's a balancing act.I am about ready to mock up this circuit on a breadboard. My LEDs are rated at 3.2v, 20mA. I am starting with just 2 of these LEDs.
If I wire them in series, what should I set my voltage regulator at? and what setting for current regulator?
Petkan:Assuming firstly there's no current regulator, use a potentiometer in your voltage regulator feedback circuit so you can adjust the output voltage. Start at about 4V to be safe, and increase from there while monitoring current. Do not exceed 20mA. In fact, don't go above about 15mA to allow for variation over temperature, component tolerance and voltage sharing. Will probably be about 6V, but beware that it will be far from linear - a small voltage change can cause a big current change. To improve voltage sharing between the LEDs, you could add a parallel resistor of say 1K to each one but it's a balancing act.
Now assuming you've got your current regulator hooked up, set the voltage regulator high enough to keep the current regulator happy (probably at least 7V) and set your current regulator at 20mA.