Newbie needs help on a project involving HC-SR04 Ultrasone sensor

Using Arduino Sensors
1

Hi all,

I'm a newbie when it involves Arduino but would like to start a project using it.
It's for a retracktable landinggear for a DJI Phantom drone.
I would like to retrackt the landing gear using the HC-SR04 Ultrasone sensor and the Adafruit Trinket 3.3V Logic mini microcontroller. But it that even possible? Can I connect the sensor to this microcontroler and use it together for my project?
Perhaps I need the 5V microcontroler version of the Adafruit Trinket?

But most important is wil this project work?
What is my project: When my Phantom drone takes off and is at 1 meter above the ground..tabel....roof...whatever surface the landinggear retrackts. On a descend and the drone is again at 1 meter above a surface the landinggear folds down.
Don't know jet what motors/servo's to use for the folding up and down action. But I need to know if my plan will work....if it doesn't....I don't need to wurry about motors anyway :wink:
The landinggear is a stock gear made out off carbon fiber tubes.
The sersor and control board must weigh as less as posible. That's why I don't want to use the Arduino One R3. It weighs more then the microcontroler...that's fore sure.
As a power source I'm hoping to use a 5V Li-Po. If anyone has a suggestion....I'm all ears :slight_smile:

The reason why I would like this project is because the stock transmitter doesn't have a spare channel left. So retrackting and visa versa must be an autonomous action.

I hope you can help me make this project a reality!

With kind regards,
Mike Wellink

2

You could possibly dispense with a controller altogether with a pulse length discriminator.

However, all that moving air and spinning props is a tricky environment for ultrasound, so I'd carry out experiments if I were you.

3

Hi AWOL,

Is this pulse length discriminator a Arduino component? Is it a stand alone unit? And what can it do?

4

Think about your problem; you need to trigger a sonar unit at say 10Hz and measure the length of the return pulse.
If the pulse is shorter than a certain length, you need to generate a servo pulse of a particular value (or perform some other action that lowers the undercart).
If the pulse is longer than your threshold, your output pulse keeps the undercart retracted.

It doesn't need a microcontroller to do that, though for flexibility I'd probably use one, just maybe not a full Arduino.

You could even remove the controller from the sonar and piggy-back or even dead-bug a small board with a different controller on it and do the whole lot there. That's probably what I'd do, if I were really weight-concious.

5

Euh....sorry....don't know what "dead-bug a small board" means. I'm just heard from Aduino about a week ago and I'm a structural engineer.....not an electro technician :disappointed_relieved:

And what do you mean by "If the pulse is longer than your threshold, your output pulse keeps the undercart retracted"?
I think I need to do some serious testing on the moment the gear should fold up or down. But isn't that setting a value in the program and see when it triggers the motors/vervo's? And tweak it as long as it needs to get close to 1 meter?

But I realy want to do all that but I need help pikking the right components.
And the HC-SR04 Ultrasone sensor and the Adafruit Trinket 3.3V/5V Logic mini microcontroller would do just fine.
I only need to know if the microcontroller can handel the input from the HC-SR04 sensor and trigger the motors/servo's?
If so...I'll go and buy them and start the assembly and testing.

6

If it's a choice, go for 5V, but yes, I think that should have enough clout to do what you want, with the provisos about noise noted above.