pic: Vex fan powered :D



It's a Vex with a high powered lightweight fan and a Msonik RV15 speed contoller that I wired myself (thankfully it didn't fry). It is capable of going 14 MPH. go to:
http://www.arkorobotics.com/images/SC.JPG
and
http://www.arkorobotics.com/images/1.jpg

you can see more images there

How fast does it go?

How does it turn? You should put a servo on the super grippy wheel there and that would be really cool.

it cant turn… this is a prototype. Next one will have an omni wheel with a flap on the back :smiley:

Which ESC are you using to drive the fan motor, and what motor are you using?

I have an entirely different project that I will be using a similar ESC to run an old RC car motor on and was wondering how well that ESC is working.

Seeing how you are using something other than the wheels to drive this thing have you considered adding pontoons so it can drive on water?

Where’s the fun if your limited to just land… :smiley:

My best guess is that it’s an Mtroniks. Perhaps the RV15 model?

EDIT: Whoa, no way. I just now read the picture description and it lists the ESC in there, and I totally guessed right. I guess I’m just WAY too into this stuff. :smiley:

Nice guess :slight_smile: , Yes it’s an Msonik RV15 ESC , It is supposedly a forward and reverse speed controller, but for some reason on the VEX set it doesn’t go backwards. That is the sort of problem you get when you take something that isn’t designed for the other and put them together… but hey where is the fun in not experimenting things like that? :smiley:

I hope I can help here.
I did some research into small ESC’s a couple months ago searching for one that would go from forward to reverse without going through a “breaking” mode first. I need it for a self balancing robot. What I found is that there are VERY FEW models out there that will do this. Most of the small units had some form of “intelligent breaking”. The unit, while running in forward, would then proportionally turn on a “breaking” FET if the control was moved to reverse. Once the ESC sensed that the motor had stopped, and the control returned to neutral, it would then go into reverse if the control was again moved into the reverse position. So, if in fact, that is how the RV15 operates, you would have to be running forward, move the stick into reverse until the motor stopped. Return the stick to neutral then into reverse again for it to run the motor backward.
The other possibility is that the ESC needs to be “calibrated” for it to know how to operate based on the signal sent to it. Many of the smaller ESC do a “self calibration”. When the ESC if first powered, it measures the PWM signal and “assumes that value to be neutral. Then it continues sampling the PWM and records the Maximum PWM it sees as “Full Forward”. The sampling continues until it sees “Neutral” again and then it records the “minimum” PWM value it sees as “Full Reverse” until it sees “Neutral” again. It is now calibrated.
So, if the cycle it sees actually goes as follows: Neutral, Full Forward, Neutral, some forward value, Neutral, it is quite possibly not providing a reverse range because it never received a " Full Reverse” value. This is a guess so please verify by reading the details of the manual.
How would you correct this in Vex? Write the initialization code to output the correct range of values to the ESC during start-up.

Wow, thanks for that I will try and read up on that. I would program it but the problem is I dont have the Programmers set.