Hello All,
This is my first post on this forum. I am in a science competition next month and have to create a electric, propeller-driven car that travels a meter in an amount of time that won't be divulged until after our vehicles are impounded by the judges. Therefore, we must be able to adjust the car on the fly at launch time. We have tried a million things and haven't had a lot of luck. We used a rheostat to adjust the voltage to the motor. We adjusted the air intake area of the propeller and even the angle of the propeller relative to the car but the results aren't near as constant as we need, sometimes varying by 30% between runs. We had an epiphany last night but don't know how to implement it.
At full speed, our car can travel the meter in about 2 seconds. We thought we might be able to use an adjustable circuit (maybe an RC with an adjustable pot) to create a delay between cutting our car on (the timers start then) and when enough voltage is delivered to the motor to make it go (around 6.5 - 7volts). We don't have a lot of electronics experience so any help would be greatly appreciated!
Here are the details:
Time requirement: 5 to 15 seconds
Voltage: 9V DC
current: App 4A
Motor/prop: standard speed 400 brushed motor and 5" prop for small hobby planes.
NO ICs allowed (I guess that means we can use resistors, capacitors, inductors, diodes etcetera).
We tried studying up on simple RC circuits and even experimented a bit but we couldn't get the motor to turn for some reason. We built a simple series circuit with a 10 ohm resistor and 1000uF cap. We attached the motor in parallel with capacitor and calculated that it should've taken app 12sec to start the motor but the prop just barely turned. Again, we appreciate whatever you can do for us.
This is my first post on this forum. I am in a science competition next month and have to create a electric, propeller-driven car that travels a meter in an amount of time that won't be divulged until after our vehicles are impounded by the judges. Therefore, we must be able to adjust the car on the fly at launch time. We have tried a million things and haven't had a lot of luck. We used a rheostat to adjust the voltage to the motor. We adjusted the air intake area of the propeller and even the angle of the propeller relative to the car but the results aren't near as constant as we need, sometimes varying by 30% between runs. We had an epiphany last night but don't know how to implement it.
At full speed, our car can travel the meter in about 2 seconds. We thought we might be able to use an adjustable circuit (maybe an RC with an adjustable pot) to create a delay between cutting our car on (the timers start then) and when enough voltage is delivered to the motor to make it go (around 6.5 - 7volts). We don't have a lot of electronics experience so any help would be greatly appreciated!
Here are the details:
Time requirement: 5 to 15 seconds
Voltage: 9V DC
current: App 4A
Motor/prop: standard speed 400 brushed motor and 5" prop for small hobby planes.
NO ICs allowed (I guess that means we can use resistors, capacitors, inductors, diodes etcetera).
We tried studying up on simple RC circuits and even experimented a bit but we couldn't get the motor to turn for some reason. We built a simple series circuit with a 10 ohm resistor and 1000uF cap. We attached the motor in parallel with capacitor and calculated that it should've taken app 12sec to start the motor but the prop just barely turned. Again, we appreciate whatever you can do for us.