ESC – Electronic Speed Controller
Here are a few tips I have picked up while researching which ESCs to put on my quadcopters.
The Basics
On a quadcopter, the flight control board’s firmware monitors measurement devices like gyros and accelerometers along with pilot stick inputs and sends signals to the ESCs attached to each the four motors. The ESCs use these inputs received from the flight control board to deliver the power required to control the speed of the motors. Each ESC has a processor, firmware and other electronics that manage this task by rapidly switching the power to the motor on and off. Continue reading for some tips on choosing the right ESC…
Max Amp Rating
Brushless ESCs are used to control brushless motors that are used on most quadcopters. The maximum amperage an ESC can handle needs to be greater than the motor/prop combination will draw. If the amperage rating is not high enough, it could overheat and die.
Other Things to Consider
Since quadcopter flight control boards need to make exact and minute adjustments to all four motors within a fraction of a second, off the shelf ESCs may not do the best job of stabilizing a quad. Two possible problems with off the shelf ESCs are:
- Not handling fast refresh rates
- ESC firmware that is not optimized for quadcopters / multicopters
Handling Fast Refresh Rates
Signals are sent from flight control boards to ESCs at rates of 400Hz or more. This translates into 400 or more updates per second. Some older ESCs may not be able to handle these update rates. The faq on the MultiWii wiki page states:
However, according to this post by Timecop at rcgroups.com, many modern day ESCs have this capability. So, while some ESC vendors advertise that they have update rates of 400Hz or greater, it appears many cheaper ESCs accept these speeds too. Whichever ESC you choose, ones that accept faster refresh rates are a better choice for a more responsive and stable quadcopter.
ESC Firmware
Even ESCs that can process high refresh rates probably have firmware that is not optimized for quadcopters. Luckily, a fellow named SimonK has written firmware that is optimized for quadcopters and it can be loaded on to many common ESCs. This requires that the ESCs be reflashed. Since flashing requires some skill, tools and effort, it may be best to purchase ESCs that have been flashed by someone familiar with the process. Here is an rcgroups post that lists a few folks selling ESCs flashed with the SimonK firmware.
For those brave enough to try it themselves, the rcgroups thread on reflashing and the open pilot wiki on flashing are two excellent sources of information about flashing ESCs with SimonK’s firmware. Beware, if it doesn’t work, the original firmware is gone forever unless you have a copy of the original code. Also, SimonK has different versions of his firmware for different ESCs and it is important to use the correct version.
Summary
ESCs should be chosen that will handle the maximum amperage drawn by the motor and prop it will drive. ESCs that accept fast refresh rates should be chosen and many inexpensive ESCs have this capability. Flashing ESCs with firmware that is optimized for multicopters is a good option to get maximum stability. However, the process of flashing requires the right tools and firmware and there is probably no going back if it doesn’t work.
[...] Présentation des composants de la carte et guide pour les débutants Une review de la CRIUS lite Un article sur le rôle des ESC sur un quadcopter [...]
I just did a short course on Embedded systems (I am a first year college student )so I am pretty new to all this stuff. I am interested in building my own quadcopter
For starting I was thinking of not using any special controller and just use Atmega 16 along with a rf transmitter to manually control the 4 motors.
As i am a starter, i am just interested in lifting off the quadcopter (not too interested in flying it around at the moment or making it stay mid air)
I was wondering whether I would be able to accomplish this basic Liftoff with using a special flight controller ?
(
incase my liftoff is successfull then I would thinkin of upgrading the quadcopter with a suitably well flight controller with gyro and all)
also I plan on using the combination of motor,ESC and battery that you have provided.
thanks
i guess you can do it without gyros etc, but it would be very hard to control. are you going to implement pitch/roll from the TX, or just throttle at first? if just throttle: all motors and ESCs etc aren’t exactly 100% the same, so it’d require tweaking on each motor motor speed(pwm) so that they all provide equal thrust. if you implement pitch/roll, this tweaking could be done by “trims” as they are called on normal RC transmitters.
of course it will lift off, but not very well. with gyros it would be way better.
let me know if i answered this right.
great site–this is so helpful. i’m interested in building a quadcopter. right now i’m having difficulty choosing a motor/esc combination. based on your advice here, i’m planning on buying these motors:
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=18151&aff=588847
and also based on your advice, i’m thinking about these esc’s:
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=4312&aff=588847
but i’m confused about the firmware/flash thing people are talking about. are there esc’s that i can buy without having to worry about having to do that? i’m a beginner, so i’m not too worried about performance right now. thanks
Thanks! That combination has worked well for me. You might want to order 1 extra as a backup. There is no reason to flash them. The standard firmware is fine. Mine aren’t reflashed and they work great. Also, the new ones come with sillabs processors and I don’t know of any alternative firmware that works anyway. Just get this programming card:
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=2169&aff=588847
What flight controller are you going to use?
Hi Britt,
What ESC’s are you using with your Naza? I finally got my quad together today and low and behold…I can’t arm it. I calibrated my dx8 in the assistant, attitude and manual modes are set etc. I spent some time on the phone with Tom from Hoverthings…he thinks my Naza is bad and said he would send a new one (Awesome service) but I’m not convinced it’s the Naza. I went the cheap route and bought 4 Hobbyking ss series 18-20a esc’s (HK-HW20a). Do you have a list of compatible esc’s for the Naza? I would much rather have plug and play esc’s too…but at a decent price. I’d rather not shell out $120.00.
Also, do you power your VC first before powering the esc’s? Do your receiver plugs from your esc’s that plug into the motor ports of the Naza have power coming from them and into the Naza?
Hope you can help. Thanks again for the great site…it was good to watch your flights.
I am using these:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=4312&aff=588847
and they work fine.
I have read about some ESCs not working and having to power them separately, either before or after the controller. I have some Dynam ESCs that didn’t work with my Naza. I never tried powering them separately. But, when I tried the same ones flashed with the SimonK code they worked.
I have no power going to the Naza from my ESC BECs. I pulled the red wires from the BECs and put heat shrink on them.
There are some posts on RCGroups on how to wire and power the ESCs seperately. I think the instructions are somewhere in this huge thread:
http://www.rcgroups.com/forums/showthread.php?t=1536553
britt,
Thanks for the help. I was able to get my quad in the air…the naza is rock solid!!!
I had to power up the naza first and then the esc’s…they seem to be working real good…considering I paid $7.62/pc.
Glad it worked. Sometimes this stuff can be a little frustrating. I am doing FPV now and I just counted five batteries that have to be charged and connected before I can fly, ha.
can we make our own (DIY ) ESC kit? have you a schema of cheap ESC
I don’t know anything about pcb manufacturing.
Colin, I had a multiwii board like that but found the multiwii firmware a little hard to configure and tune. I like a board that is more plug-and-play. The comparison chart shows features, but doesn’t really speak to how well the firmware works or how easy it is to use. The best way to get a feel for that is to read through some of the forums and see what others say about them.
Yes, the programming card is just to change settings for the esc. This post from rcexplorer shows how to use the programming card:
http://rcexplorer.se/projects/tricopterv25/tricopterv25.html
Thanks,
Britt
this one, i think:
http://www.goodluckbuy.com/mwc-multiwii-se-standard-edition-4-axis-flight-control-board-quadx-w-ftdi-basic-breakout-.html?&sl=en
according to your helpful comparison chart, it’s got good features and seems like a good starting price. at this point i’m not too worried about gps or waypoints. but gyro stabilization seems like it would be helpful.
about the programming card…i saw people comment about those, but i don’t understand what they are for. i thought they had to do with flashing the esc or changing its settings or something like that. thanks for your help.