Need help with a top secret project!

Good morning!

I work in the UAV/RPA industry as a pilot and engineer. I’m currently working on a payload project developing a working prototype for demonstration next month.
Believe it or not it is top secret but I will give you what information I can:

The end goal is to have a 12V DC motor run in pulses one way and smoothly in the other (i.e. pulse forward, smooth reverse). The pulse width needs to be manually adjusted between approximately 0.5seconds and 5 seconds and the on/off phases can be equal (e.g. 1 second on/1 second off).
Actually switching the unit on and off will be done remotely. I’m not 100% sure how yet but it may be via a small PWM signal from a payload activation cable.

So, whilst I’m great at the concept stuff my electronics skills isn’t quite where it needs to be to make all this happen!

Any ideas greatly appreciated…


Hi Mike,

Thanks for dropping by! While the onboard controller for your UAV is likely programmable, it might (will) be easier to instead use a dedicated board for this bolt-on project. Perhaps something such as the Arduino Mini / Teensy along with a motor driver, stepper motor and 12V step-up (if you don’t have a solid 12V rail already).

You’ll need either a 3.3V or 5V rail for whichever microcontroller you go with. I’m guessing you will have one of each available on the flight controller board.

The microcontroller can interpret a couple of the many spare channels that most flight controllers have, so you can bind switches on your radio to control things.

Anyhow, lots of options!

Hi Graham,

Thanks for the reply (I think we’ve met before at Newcastle FPV races).

Looks like I need to learn some Arduino stuff! It will have to be a dedicated board as the whole unit will need to be a plug-and-play solution as it won’t be a permanent fixture on the UAV.
The on-board flight controller is a sealed unit controlled through a telemetry downlink to a laptop ground-station. At the moment the only payload control I have from this GCS is a waypoint triggered on/off command (really intended to trigger camera/scanning equipment).

To give you a better idea, this is what it is attaching to: Pulse Aerospace Vapor 55

At the moment I have the prototype running on a mechanical 3-way switch that is controlled manually via a DX9 radio. This is fine for the prototype demo and to prove the concept but I definitely need a more elegant solution for the end product!

That’s more than likely! I head down to catch up with Pete at almost every event.

If you do get into Arduino stuff (well, any sort of programming) then the easiest way to connect with flight controllers is via spare servo channels. The short story; code a routine that waits for a rising edge, and then count the number of cycles (time) until that edge falls. You’ll be easily able to determine switch positions from this.

I’m not familiar with the Vapor 55, although there are some specs on that product page that are very suggestive that it has a few channels to dabble with. Side note, they list the control frequency as 900Mhz, hopefully that’s configurable between 915 MHz to 928 MHz for use in Australia.

Your DX9 is likely a 2.4Ghz device, however. you could bolt on an AR9020 for payload control.