Hiya, ITS MAKE IT FRIDAY!!
Yep, Fridays are awesome and even more so when its Sunny and I have lots of time to work on my latest Make It Project.
Things are getting exciting now, all four propellors/motors on my drone are connected and working.
However to run 4 motors – even though these are tiny – requires a decent amount of current.
In this video, you’ll see that I’ve programmed them to turn very slowly and even that is a struggle for the batteries that I’ve currently got hooked up:
You’ve probably noticed that the batteries are 3.7v lipo batteries, which is what most flying toys and robots use right? So what’s the problem?
There are few things you need to consider when choosing batteries for your application.
First and most obvious is voltage. We know from my previous post that these motors are happy receiving between 3 and 3.7v. So the battery I’m using is fine.
The current they draw is around 200 milliamps each and my battery is rated at 1000 millamp hours – mAh, i.e. 4 motors should last for an hour (this is only a very rough guage)
So what is the issue?
There is also another feature you need to understand and check when buying lipoly batteries.
They have something called a discharge rate. This is how fast they can supply the current that is needed.
The batteries I currently have would be perfect for a mobile phone, a keypad lock, a small lighting system etc. because these kind of systems use current at a slow and steady rate.
These kind of batteries are rated at 1C or 2C. Meaning they discharge current fairly slowly.
With drones and other moving robots where the current used is high and regular, a battery with a higher discharge rate is necessary.
This is usually the point where I face-palm myself and wish I had ordered something sooner so that I have a proper make it day. However, I’ve just remembered something. Last year, when I first became fascinated with making something that flies (flys?) I took apart a toy helicopter and guess what??
Yep, I still have the battery for it, in fact, I have 2! (remember what I said about being organised? lol, it pays off!)
I’ve taken the battery out of my current bought drone, a small parrot one, which is what my own one is based on.
You’ll see that it has discharge rate of 15C and is rated at 550mAh. This drone usually flies for around 5 – 10 mins.
The batteries I have are rated at 20C and 680mAh, this means flight time might be more. But I will be using two of these batteries in series as that will allow me to run all of the logic side – i.e. the microcontroller and motor drivers from one power source.
I am conscious of the fact that this drone is going to be heavier than the parrot drone…I’m looking forward to finding out whats going to happen…
My next step is to connect the batteries together and sort out that terrible mess of wiring on the controller board…see you soon!