Arrma Diff Brain with Spektrum

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Arrma RC's
  1. Infraction
I have the Spektrum DX4S and an SR310 receiver. Here's how I got it working with the Diff Brain.

RX Setup:

White plug from Diff Brain goes to Aux1.

TX Setup:

Assign your preferred switch on the controller to Aux1 3P.

Set Aux1 travels to 150%.

Set Dial (knob) or another switch to Aux1 Trim+

Set Trim Step on Aux1 to 20.

That's it! The Diff Brain should now be functional by using the Aux1, three position switch to cycle through the modes. The center position will make a servo chatter until the knob or trim switch is set to max trim in either direction.


IMPORTANT! Disconnect the motor leads before testing the modes.

Position 1 should be Blue. All diffs unlocked.
Position 2a (Dial anti-clockwise) is Green (Wheelie Mode) Center diff locked.
Position 2b (Dial clockwise) is Yellow (Drift mode) Rear and Center diffs locked.
Position 3 is Red (Climb mode) All diffs locked.

Connect the motor leads and test it off the ground. Run through all the modes and make sure it allows you to run them at max speed.

Extra bits:

I tried a trim mix on a separate 2P switch to select between green and yellow modes with a single button press in either direction but it was not reliable after cycling power. The knob works best for me.

And if that's not enough, I made a video too. :watching:

Have fun out there!
nice!! now I need to get a dx4s I was looking at my dx4c a few days ago wondering if I could get title to work somehow.... I just got a bunch of spektrum recivers almost all my trucks run on them now....
I also have a Spektrum DX4S, and SR410 receiver. I came up with a different way of using the diff brain to where you don't need to use the trim knob to adjust. Just another option, I'm not saying there is anything wrong with the way that MetalOne did it, use whatever works best for you. The one problem is that this method will use up both Aux channels to make it work, so if you were looking to use AVC, this may not work for you. I guess you have to choose your poison. My first car came with AVC and it was winter time here in the Pacific NW, so the streets were really wet most of the time. It definitely helped me as a new driver, but I was quickly turning it down as I got better at controlling the throttle and steering on my own. After a couple of months I completely turned off AVC, got the Spektrum DX4S and just added in some expo to the steering for high speed runs and haven't driven anything with AVC since. I like being able to drift my cars when I want to

For my setup, I happen to be using Switch A and Switch F to control the Diff Brain. You can use whichever ones you want, I just found this convenient for me.

Travel Setting:
Set both AX1 and AX2 to 150%

Switch Setting:
Set Switch A to AX2 2P, (sets Switch A to a 2 position switch). (I also reversed AX2 channel to get the switch direction the way I wanted it)
Set Switch F to Mix A

Mix A:
Set Master To AX2
Set Slave To AX1
Set A Value to 100% 100%
Set B Value to 32% 32% (You toggle between A & B by hitting switch F, the button next to the roller)

That's It.

If you go to the Monitor screen you can watch the value on AX1 to see what mode you are in. The Bar Graph will give you a quick indication as well.

-2000 = All Diffs unlocked
Hit button F
-664 = Center Diff Locked
Hit switch A
664 = Center and Rear Diff Locked
Hit Button F
2000 = All Diffs Locked

If you play around with it, you can get the feel for how to move between the different settings.

Hope some of you find this useful.
Very nice! As I mentioned, I tried to get a mix working for a second toggle but I couldn't make it reliable after cycling power. I didn't mess with it much after I got the knob working. That is awesome!
hi there , do u think its also possible with the spektrum dx4r pro.

many thanks
Yep. The LHS uses a DX4R with their Nero.

There's a DX5R now. Gonna sell for $299. I want it!
This post helps me out big time as my diff brain and other micro servos are arriving today and I will be tackling the install with my DX4S this weekend. I built/building my Nero from parts so working with what I have already so no tactic controller to begin with and only was running one micro servo on the center diff so far on aux1 directly. Can't wait to try out the methods above and test out the various beast modes. Love the knowledge and helpfulness of the members on this forum!
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