Model airplane power supply

I have a problem, I need a power supply for my model airplanes. I am learning electronics but it is difficult.
What I need is a power supply that uses capacitors to power a motor for up to 15 seconds. If I use a battery it could fly for 3 minutes, in which time it can get out of sight. The output smoothness doesn't matter as long as the device produces alot of power for 10-15 seconds. The motor is 1.5-3.0 vDC and has a 0.98A current draw at maximum efficiancy. This doesn't matter much because the power supply might fluctuate and I could run the motor at more than that. But idealy that is how the motor should be run.

I could also run a small rechargable battery and drain that very fast as long as it supplies the power I need. But i still don't know how to do it.

Any help would be greatly appriciated.

Where are you? In the USA, the national modelers club (AMA) has a section for indoor models and very light models for outside. They sometimes use supercapacitors for power. You might also want to consider CO2 power. If you are in another country, there are equivalent organizations, but I do not have contact information for them.

It sounds like you have very little experience with such models, which is why I recommend that you get in contact with others who have more experience.

John

henradrie said:

power a motor for up to 15 seconds.
The motor is 1.5-3.0 vDC and has a 0.98A current draw at maximum efficiancy.

Click to expand...

C = i (dT/dV), and in this case i = ~1A, dT = 15 sec, dV = 3-1.5=1.5v and so C = 10 Farads.

Powerstor makes supercaps that will work. Two of the 22F 2.5 volt units in series for 5volts at 11F will work nicely. Cost around 35 dollars.

The voltage of a discharging capacitor drops sharply and quickly. That is why electic model airplanes use Li-Po or Ni-MH batteries that keep the voltage and power high until they are almost dead.

Thanks guys for your help. I just found out that the motor is to underpowered for the job. I will keep the supercapacitor idea in mind though. I was wondering if I could use a small battery and drain it really fast. I read another post where someone used one AA to power a circuit that needed 2 or more AA's. The drain time is the problem here. Could I drain a small rechargable battery in 15 seconds?

Might be an idea to use a normal battery with a timer circuit.

Might be worth looking into, I've never seen any compact boost converter circuits out there for 1.5 volt cells except 'joule thief' designs which are for pulling the last few mas out of a dieing 1.5 cell. Try lithium polymer cells for micro RC helicopters perhaps, there you at least have 3+ volts to work with at the start. The switching losses aren't even an issue, but for logic, a single diode drop the power has to pass through is 1/6th of your total voltage, which is a LOT of power. FETs don't work so well at voltages this low without dedicated drive cirucuitry.