# Blimp Project: Is it possible to control using 3 Motors and differential thrust?

A few friends and myself are currently working on an Arduino controlled RC Blimp.
We already have a hull (2,2 m long, 0,8 m diameter) that has a rough lifting force of 200 g.
The next Problem, that needs to be solved is how to control such a Beast. My current idea is an Arduino Joystick (like this: arduinolearning link) and a sliding potentiometer to get an x, y and Speed input, convert that to 3 motor commands to input to an L298N Dual-H-Bridge to control 3 motors. The first motor on the bottom left, one on the bottom right and one on the top. The current plan is to use an Arduino UNO as a remote, sending the motor commands to a 433 mHz transmitter and receiving it with a 433 mHz receiver connected to an Arduino Pro Mini which tells the L298N motor bridge what the output for the motors should be. As we are all just pupils with limited to no programming knowledge we need quite some help to write an algorithm which transforms the 3 inputs to 3 x 3 outputs (each motor needs two inputs for direction and one for speed). The rest of the code should be easy enough, so that we can learn it with tutorials and other project code.
One last thing is that we also don’t really have much electronics knowledge, so if there needs to be a resistance anywhere, tell me, please.

I will attach a schematic for the whole thing from fritzing.

200 grams? you didn't tell us about the battery to power all this equipment. Have you weighed the all the devices you are listing as needed?

Paul

Lesson #1: that's not a schematic. Fritzing can let you draw schematics, but you have to switch from "breadboard view" to "schematic view".

PaulRB:

Lesson #1: that's not a schematic. Fritzing can let you draw schematics, but you have to switch from "breadboard view" to "schematic view".

Well that's a small translation mistake and i beg your pardon for it.

Paul_KD7HB:
200 grams? you didn't tell us about the battery to power all this equipment. Have you weighed the all the devices you are listing as needed?

Paul

Yes, although the Latex Hull is alredy subtracted from that, so that would be 200 grams for Electronics and mounting.
I have not yet decided on what capacity battery to use, but it will be a single cell LiPo (3.7V) hobby accumulator (like in RC planes) as the Arduino Pro Mini i ordered is the 3.3 V version and the Motors are rated to be used with that voltage.

The L293 are poor choices for motor controllers with the 3.7V battery.

From the L293 datasheet

10 Power Supply Recommendations VCC1 is 5 V ± 0.5 V and VCC2 can be same supply as VCC1 or a higher voltage supply

Maybe something like this among others.

groundFungus: The L293 are poor choices for motor controllers with the 3.7V battery.

From the L293 datasheet

i saw that earlier too, but i couldn't find a better choice, can you recommend something? Also we are not sure if we shouldn't get bigger motors to maneuver this thing outside.

I edited my last post with a link. Pololu has other choices as well.

You might want to consider brushless DC motors (and compatible drivers [ESCs]) like are used on drones and quads. Higher power to weight than brushed motors.

groundFungus: I edited my last post with a link. Pololu has other choices as well.

thank you! But me being a German means i have to pay at least 18\$ shipping and wait for weeks if i order from them.

If I were conltolling a blimp with 3 channels, I would use 2 motors and a servo.1 motor on each side of the gondola mounted on a shaft that would let the servo turn the shaft, pointing the motors up, forward or down. Differential thrust on the motors for turning.

vinceherman:
If I were conltolling a blimp with 3 channels, I would use 2 motors and a servo.1 motor on each side of the gondola mounted on a shaft that would let the servo turn the shaft, pointing the motors up, forward or down.
Differential thrust on the motors for turning.

I have seen blimps being controlled like that, but as we are a group of students spending our free time with this project we also want to make something new, that you can’t buy in a store and that (to our knowledge) hasn’t been done before (obviously not the blimp idea, but the 3 motor thing)

rehreh: I have seen blimps being controlled like that, but as we are a group of students spending our free time with this project we also want to make something new, that you can't buy in a store and that (to our knowledge) hasn't been done before (obviously not the blimp idea, but the 3 motor thing)

Are you all not forgetting one important parameter that a blimp must control. It starts with the letter "B". How do you intend to control that function?

Paul

For this scale, the goal is anything close to neutrally buoyant. Then use motors to control flight direction including altitude.

vinceherman: For this scale, the goal is anything close to neutrally buoyant. Then use motors to control flight direction including altitude.

Neutral buoyancy is a phantom. As soon as the blimp warms, it will rise. You will have to release gas to maintain neutral buoyancy. If you fly it inside a large room, gymnasium perhaps. It will soon be at the ceiling with no way to get it down until the room cools.

Paul