View Full Version : Airtronics M8 fix for ESC Arming - Tip

12-06-2008, 04:06 PM
A while ago I bought a used Aritronics M8 with a Spektrum Module. This was to use in addition to or as a replacement for my Spektrum Dx3. The M8 has ten model memories and looks really cool so I was looking forward to using it.


To make use of a different transmitter on whatever RC rig that I had previously used with my DX3 I had to bind the new transmitter to the receiver. Simple enough, it worked fine once I remembered how to work the bind buttons.

This is when the trouble started. The Mamba Max wouldn't arm. I read through the instructions then tried several times to calibrate the ESC but it wouldn't work. I set the throttle end points out as far as they would go as suggested in some forums, but I still couldn't get it to work. Then I had a look at the throttle trigger. This seemed strange. The center position is not really at the center of its entire throw. It is more like at about 20% of the throw. I suppose that this makes for much more control or resolution for your throttle when you are going forward. To recap, about 80% of the throttle control movement is used for the forward direction and 20% for reverse.

What does it mean when we are calibrating or arming an ESC?

The ESC needs to know three things for it to work. It needs to know when your finger is off the trigger, when you are at full throttle and when you are at full brake. When you do the calibration procedure for your ESC it has you go into each of these modes so that it can store these settings internally. If you calibrate your ESC for a particular transmitter and then use another that has its end points and trim set slightly differently, it might just take off on you or maybe give you less than full throttle when you call for it.

Well, at this point, I have a really cool transmitter but my Mamba Max refuses to work with it. I did some investigating. I plugged a servo into the throttle channel of my receiver and watched what sort of motion I could get from the throttle.


This picture shows the range of the throttle control when the Airtronics M8 transmitter was used. I'm not an artist, but you get the idea I hope. I show three servo horns. The servo sits at Noon when the throttle is at rest, at about 11 o'clock when in full reverse and at about 2 o'clock when in full forward.

Next I connect the Spektrum Dx3 and tried again. This shows that when in full reverse, the servo is deflected a lot further. The full swing looks more like a Timex watch commercial with the hands pointing at 10 and 2.

So now I think I am on to something, but what can I do about it? I took apart the M8 to see if I could somehow modify the trigger to give more swing in the reverse direction or maybe just move the "rest" position more towards the center but it looked more complicated to modify it in that manner than I was willing to do. So I went back into the M8 menu system some more and moved the reverse end point out more and tried to move the sub trim to get the "rest" position more in the center and it helped slightly, but not enough to get the Mamba to arm.

Fixed it electronically!

The throttle control is just a potentiometer. What I did was put another pot across it and used it as an extra trim control. This allowed me to get the rest point more in the middle of the total servo swing and then the Mamba calibrated! :luxhello:

This is what the servo swing looked like after installing and adjusting the pot.

Next time I have the transmitter apart I will post a pic of the pot that I installed in parallel with the throttle.

Sorry this was a long rant to get to the point, but hopefully it gives you some idea of things to try if you are having trouble getting your ESC to arm.

12-06-2008, 07:16 PM
ya i had this problem big time..i was ready to light my hair on fire..lol i couldnt get 2 different mamba,s to fire up..yet i,ve had this radio for some time and it never was an issue before..this is some good info here..i think it cant find neutral, 1 fix might also be to advance your throttle trim up a bit so it finds nuetral which is not were it would be in a 50/50 trigger setup good research Al:rock:

12-06-2008, 07:30 PM

I tried the throttle trim but it just couldn't get it close enough. The extra trim pot I soldered internally took care of it.