Science Buddies: "Ask an Expert"

Can someone point me in the direction on how (or if) I can easily build this circuit? We have a wind turbine project that we would like kids to measure their lung power with. We have used the string and weight and measured the distance. Now we'd like to add electricity to the mix. We have magnets and coils attached to the turbine to generate the electricity. Now we'd like to show the strength in a more fun way than measuring with a voltmeter. We were thinking building an LED bank of 10 LEDs where the more power generated, the more LEDs light up. Any idea if there are some sort of devices - transistors or ICs - that we could use to do this? Any ideas would be appreciated. Thanks

kalipt - There are simple IC's that will do the analog input (voltage) to 10 LED display drive capability. The National Semi 3914 is an example. Attached URL is a good explanation of how it works. A few things to consider. The output of your generator is probably not going to be linear, so trying to relate actual power generated to the output voltage (or number of LED's that light) won't be accurate. You mentioned magnets and coils as part of your generating mechanism. This sounds like you will be producing an alternating current (AC) output. This circuit wants to see a DC input voltage. You might consider using a cheap DC motor as your generator rather than rectifying the AC. The LED you are driving now requires DC, so you are just seeing it light during the half cycle when the polarity is correct.

http://www.electronics-project-design.c ... phLED.html

Rick Marz