Hi guys,
I've got a little project with a solar kit, that came with a solar panel and a small engine. The specs for the panel say it outputs 0.9V at approx. 400mA.
I want to replace the solar panel with a battery or a cell phone charger. Now, I've used a multimeter to measure the voltage the panel was generating, and I'd say a good "slow" spinning speed would be at 0.2V, while a good "fast" spinning speed would be at 0.6V. I want to use the pot to modify the voltage supplied to the engine by the battery, using those two values as minimum and maximum.
So, if I want to use a 1.5V battery as the power source, I'd need a resistance of (1.5-0.2)/0.4=3.25ohm for the slow speed and (1.5-0.6)/0.4=2.25ohm for the fast speed, right? This leads me to conclude that I need a low resistance pot or otherwise the "slow" and "fast" settings would be too close together.
I looked at pots at RadioShack, and the lowest they have is the 25ohm, 3W. But a 25ohm pot in this case would need to handle (0.4^2)*25=4W, right?
Would using other voltages (say, 9V) make it easier? I think I'm missing something here...
I've got a little project with a solar kit, that came with a solar panel and a small engine. The specs for the panel say it outputs 0.9V at approx. 400mA.
I want to replace the solar panel with a battery or a cell phone charger. Now, I've used a multimeter to measure the voltage the panel was generating, and I'd say a good "slow" spinning speed would be at 0.2V, while a good "fast" spinning speed would be at 0.6V. I want to use the pot to modify the voltage supplied to the engine by the battery, using those two values as minimum and maximum.
So, if I want to use a 1.5V battery as the power source, I'd need a resistance of (1.5-0.2)/0.4=3.25ohm for the slow speed and (1.5-0.6)/0.4=2.25ohm for the fast speed, right? This leads me to conclude that I need a low resistance pot or otherwise the "slow" and "fast" settings would be too close together.
I looked at pots at RadioShack, and the lowest they have is the 25ohm, 3W. But a 25ohm pot in this case would need to handle (0.4^2)*25=4W, right?
Would using other voltages (say, 9V) make it easier? I think I'm missing something here...