Connecting multiple controllers

[Cyscrofer]

Hi guys.

A ? For all you brain boxes out there.

I'm building a project and the plan is to use 4 ds120 Rhino2 controllers on one vehicle.

Motor wise 24v 1500watt on each corner.

OK controlling them....

What do you guys suggest I do to control all 4 controllers all at once using a single wig wag type of control.

My only thought is using some dc to dc circuit that give say 0v to 5v maximum say at 3 amp output and use the voltage adjustment preset ore variable resistor like on a wig wag...say 10k.

My concern is tapping 4 controllers together.

Do I use signal diodes to stop feedback from each of the Rhino controllers?

Any hints tips or circuit designs would be a massive help

Cheers Chris

[Burgerman]

Motor wise 24v 1500watt on each corner.

How many times. 1500 watts tells us nothing at all. It doesent tell us the motor stall current. It doesent tell up the peak torque output or the maximum watts. IOr the free running current.
You need to know the stall current. And free running current. And the max torque you will get at the controllers max amp output. That will be MUCH less than the motors stall current if the motors are of a low enough impedance.

OK controlling them....

What do you guys suggest I do to control all 4 controllers all at once using a single wig wag type of control.

Yes.

My only thought is using some dc to dc circuit that give say 0v to 5v maximum say at 3 amp output and use the voltage adjustment preset ore variable resistor like on a wig wag...say 10k.

No idea what this means.

My concern is tapping 4 controllers together.

Do I use signal diodes to stop feedback from each of the Rhino controllers?

You are only connecting the BATTERY input. And the wigwag voltage swing input right?
What would the diode be for? Thats an input it has no output other than the 5V/0v that you will take from 1 controller.

[Cyscrofer]

Very sorry for being thick here...I've only 35years to fall back on so here goes.

24v 1500watts .....don't mean squat.
It doesn't have to.
62.5 amps max draw under full load.
That's about as much as you need.
Running 4 of these motors on 1 buggy ain't ever gonna draw max current unless I put it upto a Brickhill and try and push it over.

Stall current motor hysteries and all that technical waffle doesn't have anything to do with the question.

I'm planing on using 4 ds120 controllers.
1 for each motor.
That way I'm not gonna strain anything and bugger anything up.
Yes all the controllers connected to a pair of 75aH gel batteries

The main question is connecting 4 controllers together on the speed control side of things.

Electronics being electronics and since I'm not qualified on these type of circuits to state what's the right thing to do when joining 4 inputs together so for safety 4 diodes to block any feedback from each controller seems to me to be a safe idea.
The last thing I want is 1 controller to go down and effect the other 3 sending me off in to a hedge or something far worse.
A safety thought....thats all.

So if I just join 4 input together can I run then off one wig wag with no circuits needed?

[Burgerman]

Where are you planning to put this diode?
You cant put it on the voltage out to the pot as then your 5V will be 4.6 or 7. You cant put it on the wiper out as you will lose .7 ov a volt. Beats me..

Yes that wiper input is just looking for a SIGNAL voltage. Nowhere near your 3A supply. Its a tiny tiny current. Into maybe a 100k input. So take the 5V and the 0V to your wigg wagg. And take the wiper out to all 4 controller in a screened cable.

As for

24v 1500watts .....don't mean squat.
It doesn't have to.
62.5 amps max draw under full load.
That's about as much as you need.
Running 4 of these motors on 1 buggy ain't ever gonna draw max current unless I put it upto a Brickhill and try and push it over.

Thats nonsense. Your 1500 watt motors will try to draw maybe 300 plus amps as you accelerate. Or if a wheel os stalled. The 1500 watts thing is nonsense. They will have an impedance around 25 to 35mOhm. Add 24V and you get 800A according to ohms law. And thats around double what a wheelhair motor draws at 24V stalled. It cannot do that only because it is limited by the max current on your controller. This reduces torque by maybe 8x due to a 100? Amp limit. So if you plan on going up anything steep, or having a sensible acceleration rate, or not having the battery voltage collapse every time you gun it then your max speed better not be high. It will work OK at maybe 8 to 12MPH. Your battery range will be dismal.

62.5 amps max draw under full load.

My RC car has a 50A limit. My RC helicopter regularly sees 125A on a rapid climb. My quadcopter sees 85A every time I accelerate upwards. 62.5? Wher are you getting this?

This is the R-Net software. LOOK at the motor current on my TWO motors, as I turn in place on a wheelchair with 2x 350 watt motors. One is over 100A the other is 114A. You are talking about 1500 watt motors. With much higher current/lower impedance. 62A??? You are on another planet.

[Cyscrofer]

OK thanks
Control side perfect

Controller wise I'm very limited on my options.
Being very limited on what's right my grand idea which is getting more holes put in it every time I talk on here was to run motor I could actually get hold of
The 1500watt motors will never pack in although yes I'm never gonna get anywhere near running them at full power.
Ii used smaller motors before and burnt several out so this time plan on doing this only one more time.

I dont know all the stall currents and general running data on the motor gearboxes.
I'm having them custom built as we speak.
The company who make them use them on about everything they produce...wheelchairs to golf buggies so thought that's a good start.
There running into MnRV063 gearboxes with 5to1 ratio

They tell me on the diameter wheels I'm running I should get a decent top speed and if I use individual controllers then the current required for off road use should be fine.
I'll I can do is try...I'm sure when you first started build you buggered a lot of things up but over time you learn as you go.
So that's where I am.

Thanks for the help though at least you have cleared up the control question I asked.

[Burgerman]

Ii used smaller motors before and burnt several out so this time plan on doing this only one more time.

Why do you think that was?

(Amps! = heat) and you are overloading them. That motor watts thing tells you quite literally nothing useful.
I have a tiny motor in my hand that I use in a high speed model plane from my bench. It is 24mm (1 inch) diameter and 1 and a half inches long. It draws 125A in flight. And is rated as 700 watts. We actually run these at 1200 to 1500 watts.

How do I know? Measured!
And Ohms law. 125A X 12V (3S Li Poly) = 1500 Watts.

[Cyscrofer]

Wow....
I wasn't aware that it would be so great.
So what would yiu recommend I do.
I might still have chance to reduce the size of motors before they get shipped.

This is becoming a nightmare not a project.

[Burgerman]

There isnt anything you can do other than accep that you will need a relatively low top speed. That reduces motor current in direct proportion. It will load them less because you have 4. But it will still need a lot of current at 30mph. Wait till you try a hill. And seriously, 75Ah lead batteries will be destroyed in short order! They struggle to manage a simple 6mph powerchair.

The only alternative is to keep the short slow gearing, and so low current/high torque and use more volts to get the speed. As does every EV on the market.

Why do you think that things like the tesla car is not using 24V? They are around 400V. And porche EVs use 800V.

Why do you think that in order to get a 16MPH wheelchair I used 24V 8mph motors with double the voltage? Becase it retains the torque, and low current requirements of the 8mph powerchair at all speeds and yet it does 16mph. Theres no penalty. Had I used 24V and 16mph motors it would have doubled the Amps needed at ALL speeds. And that would have meant an overheated buned out motor, half the peak torque, etc. And half the range.

Have a read. Carefully. http://www.wheelchairdriver.com/BM-MK3- ... rchair.htm

As they say on the EV forums Volt up, gear down.

[slomobile]

https://www.dynamiccontrols.com/sites/default/files/2018-05/Rhino2-Installation-Manual-Issue-3_0.pdf
General wiring configuration on page 17, answers to your question are on pages 33 and 36.

If the throttle potentiometer is powered externally (not by T+ and T-), take extreme
care to avoid ground shift. The RHINO2 can interpret a ground shift voltage as a
drive signal and the scooter might start driving. If the throttle must be powered
externally, either use additional hardware as described below or use the Neutral
Detect feature (see 3.10.3) to detect a ground shift and prevent a potential
runaway.

Pin 1 TW is connected in parallel to all 4 controllers and the wiper of the single throttle potentiometer.
Pin 8 T- is connected in parallel to all 4 controllers and the - of the single throttle potentiometer.
Pin 2 T+ from ONE CONTROLLER ONLY is connected to the + of the single throttle potentiometer.
Pin 13 B- of each controller needs to be joined together at the same point to the battery - terminal with similar length wire.
TW and T- wires should also be similar in length and joined in a star configuration at a single reliable point.
No diodes required.

You can do a similar thing if you use dual inverted throttle potentiometers. The advantage of dual pots is that a fault will be set and the scooter will stop if either potentiometer fails, safely alerting you to the problem, but leaving you stranded. A single pot, if it fails will just send the scoot at whatever throttle level it sticks at. Usually open wiper, so the random open circuit voltage read by the controller could be anything, including an over or under volt condition which would also set a fault and stop the scooter.

[Cyscrofer]

Thanks.
Looks like a dual pot set up is a must with added protection just incase.
Thanks for the wiring information

I would of loved to stick 48v on board but 4 batteries isn't light and I'm not sure how far you can push the ds120 controllers...probably not very far before over voltage trips it up.

I can't get the motors changed yet as there already out for delivery.
Maybe long term I could drop the wattage to 500watt each.

I will have to see how it goes.
Thanks for the help.

[slomobile]

A dual pot setup is NOT necessary. It just depends on how you want your machine to behave if hardware fails. Either way, you aren't going anywhere. I think most scooters and wheelchairs just use a single pot. Unless you are refering to the second pot being a speed limiter. That is a different thing. The dual pot I was referring to was just an option on that particular controller. I would not recommend the dual inverted pots.

[ex-Gooserider]

Also you want to set the 'travel' on the pot input to be LESS than the full range, and having a bit of margin on each end - i.e. if you have a 0-5V swing, use 0.5-4.5V as the maximum control range and treat anything outside that range as a 'shut down' level error....

This gives protection against open circuits or shorts.... It is fairly standard practice so there should be no problem programming the controllers to match. (Use the 'maximum travel' calibration routine)

The other big concern that I could see with using 4 controllers in parallel is whether all 4 will put out the exact same output for the same input, and likewise will all four motors run at the same speed for a given output - if they don't match on both, you will have the slower motors acting as brakes on the faster ones - how much of a problem this will be probably would depend on how far 'off' they were.

You might also want to think about trying to have some sort of 'differential control' so that you don't run into issues w/ the wheels needing to be running at different speeds when turning. (I.e. the same thing a car differential does)

ex-Gooserider