Using 2 Pots for input on a controller ?

[snoko]

Hi Everyone hope your doing fine

I have another related question to my ongoing project - this time regarding the controller / pot / rheostat setup thats used in mobility scooters so I can use it for my kneewalker / bad hands to have the option of a set resistance via the rotary pot and also a acceleration ( possibly reverse ) via finger throttle .

My problem however is that all the controllers Ive been looking at or had considered ( Kellys minifor a brushless hub or RoboeQ's for a CIMs motor) only seem to allow for one type of pot input rather than two I would need.

I know this possible -or assume it is - because almost all mobility scooters have this setup of a rotary pot and rheostat yet Im having trouble finding any controller that can fit my needs.

Is this something then exclusive to each brand of mobility scooter or is there some way its possible to adapt or use generic controller this with a brushed or brushless motor ? ( Perhaps with something like a micro controller )

thanks

snok

[Burgerman]

you are going to need to make this clearer before I can help.

What are you actually trying to do?

The roboteq for eg, can use many types of input, from voltages (you choose) and frequencies, pulse widths, duty cycles, and can be run like a servo with feedback loop etc.

[snoko]

you are going to need to make this clearer before I can help.

What are you actually trying to do?

The roboteq for eg, can use many types of input, from voltages (you choose) and frequencies, pulse widths, duty cycles, and can be run like a servo with feedback loop etc.

I was planning to use the roboteq with an analog input in serial for use with a CIM motor ( 12v ) and 10k rotary pot ( 5 turn ) , but I also want a finger throttle I can use for more range of speed , so I dont have the hassle of having to turn the pot all the time ( not always easy if steering ) to accelerate or slow down.

The problem with other throttles ( like used on ebikes ) is their all twist or thumb so its impossible to keep a steady cruise rate without gripping and holding it in position which is almost impossible for me to do unless I add some adaption ( like this one I planned ) so thats why Im not that high in those sorts of controls - far better I have something I can set and leave , and alter at my own choosing.

The AX3100S should be able to handle two CIM motors I think
- 30s: 120A
- 1min: 100A
- 3 min: 80A
- 1h: 80A

The CIM consumes 20-25A, so two of them would consume 50A, which is less than 80A (which that controller can sustain for 1 hour). When climbing a slope, the current can increase to 100A, and that's fine so long as it's not for too long.

It also lot of built-in protection, as you know.

snok

[Burgerman]

All good. But what are you asking?

My problem however is that all the controllers Ive been looking at or had considered ( Kellys minifor a brushless hub or RoboeQ's for a CIMs motor) only seem to allow for one type of pot input rather than two I would need.

I know this possible -or assume it is - because almost all mobility scooters have this setup of a rotary pot and rheostat yet Im having trouble finding any controller that can fit my needs.

The controller doesent do this. It still has a voltage swing input.
You need to build your "front end" to do whatever you want your controls to achieve, and then the result of this is fed to the controllers input. So for eg you would have a finger trigger, that gives the full 5v swing for forwards, or reverse, and you would change its range via a divider network which would be your rotary control. This can be total volt swing, or it can reverse it, or it can be eny part of the plus/minus 5v that is the full forward/reverse that controls the vehicle.

The point is that its your input circuit that does this, not the controllers input.

[Burgerman]

EG when indoors, my roboteq joystick will have a rotary knob so its speed can be reduced to say 2mph max. From 15. This will simply be a reduction of total volt swing due to an additional rotary pot.

Or I may do it on a switch, so it switches in 2 resistors to the ends of the pot when I want to go slow. Or a single one on the output. You can switch on or add via a pot, delay too, by adding a small capacitor that smoothes the joystick or pot output a little when carers or other people are driving it about... This is all simple analog electronics.

[snoko]

All good. But what are you asking?

My problem however is that all the controllers Ive been looking at or had considered ( Kellys minifor a brushless hub or RoboeQ's for a CIMs motor) only seem to allow for one type of pot input rather than two I would need.

I know this possible -or assume it is - because almost all mobility scooters have this setup of a rotary pot and rheostat yet Im having trouble finding any controller that can fit my needs.

The controller doesent do this. It still has a voltage swing input.
You need to build your "front end" to do whatever you want your controls to achieve, and then the result of this is fed to the controllers input. So for eg you would have a finger trigger, that gives the full 5v swing for forwards, or reverse, and you would change its range via a divider network which would be your rotary control. This can be total volt swing, or it can reverse it, or it can be eny part of the plus/minus 5v that is the full forward/reverse that controls the vehicle.

The point is that its your input circuit that does this, not the controllers input.

So what do I need to use as the input circuit in order to do this ? ( if I wanted it to be any part of the plus/ minus so I had full control )
Would I still be use the rotary pot by itself if I wanted , or would I be dependent on the trigger for throttle ?

thanks again,

snok

[woodygb]

I'd suggest a complete control system from something like a small mobility scooter.

E.G. The Pride GoGo ..you'd get EVERYTHING you seem to require ...a Wig Wag throttle ( pot ) forward and reverse... together with a Speed limiting pot.



IF you look at the pic ( PGDT S-Drive Controller )it's VERY simple ... on the control side you could actually have just the ON/OFF switch and the 3 pot connections.

[Burgerman]

That would work.

But all he really needs is a couple of pots going in to one input. Not quite sure yet what he wants to quite do what, so cant really advise how to connect it.

But two pots (rotary, and trigger) and a few resistors is all thats needed as far as I can see.

If he wants to use a rotary one for speed control (not to limit speed) then he can. And the trigger to over ride this, and one series diode would allow that. Or is it one or the other? Or is it a speed limit? Not sure what he is trying to achieve. Not clear. But in all cases it can be done easily with a couple of passive components.

[snoko]

EG when indoors, my roboteq joystick will have a rotary knob so its speed can be reduced to say 2mph max. From 15. This will simply be a reduction of total volt swing due to an additional rotary pot.

Or I may do it on a switch, so it switches in 2 resistors to the ends of the pot when I want to go slow. Or a single one on the output. You can switch on or add via a pot, delay too, by adding a small capacitor that smoothes the joystick or pot output a little when carers or other people are driving it about... This is all simple analog electronics.

Yes thats what Im looking for ( your first example ) but with finger throttle instead.

Do you have any links for your other explanation regarding the setups you mention, like schematics for reference - not exactly that well versed in resistors yet or familiar with various wiring schemes and what they can achieve.

snok

[snoko]

I'd suggest a complete control system from something like a small mobility scooter.

E.G. The Pride GoGo ..you'd get EVERYTHING you seem to require ...a Wig Wag throttle ( pot ) forward and reverse... together with a Speed limiting pot.



IF you look at the pic ( PGDT S-Drive Controller )it's VERY simple ... on the control side you could actually have just the ON/OFF switch and the 3 pot connections.

I take it thats the ground going to the limiter pot from inhibit connection , and 5v going straight to the Throttle from the + battery ? ( sorry im bit slow on these things no thanks to suffering from Dyscalculia )

snok

[woodygb]

The main Wig Wag throttle pot has 0v ( pin 8 ) on one end and 5v ( pin 2 ) on the other ...the wiper ...when centered ... will have a value of 2.5v ...so the volts swing/range is 0 to 5v with 2.5v being neutral/off and any value above or below this will be a forward or reverse speed.

The speed pot is inserted into the wiper feed from the main Wig Wag throttle pot ... this reduces the max and min voltage values supplied to the controller and thus max and min speed.

[snoko]

The main Wig Wag throttle pot has 0v ( pin 8 ) on one end and 5v ( pin 2 ) on the other ...the wiper ...when centered ... will have a value of 2.5v ...so the volts swing/range is 0 to 5v with 2.5v being neutral/off and any value above or below this will be a forward or reverse speed.

The speed pot is inserted into the wiper feed from the main Wig Wag throttle pot ... this reduces the max and min voltage values supplied to the controller and thus max and min speed.

Thanks, so from what I see that pin 5 ( inhibit ) is the one that basically acts as block or 0V,
so the actual flow gets redirected through the speed pot instead and altered which in turn affects the speed .

So I assuming what BM suggested earlier was to simply use a diode to compensate for that pin 5 that usually inhibits the flow - correct ?
snok

[woodygb]

Nope ...just leave everything EXACTLY as it is.

[snoko]

Nope ...just leave everything EXACTLY as it is.

Ok I see what its for now , so it has nothing to do with the redirecting the flow , ( I guess its obvious with - not being where it is )its only used when charging the battery.

But why are there arrows going from the negative side of the battery back towards the throttle /Wiper when there only one wire, is the electron flow reversed ? (( confused ))

snok

[woodygb]

The center arrows are the pot wipers ... the others show mechanical movement of the pot wiper along it's track.

pot wipers.jpg (45.17 KiB) Viewed 4273 times

Here's the same thing ..just a slightly different wiring setup... it doesn't SHOW the speed limiting pot but does mention it.

[woodygb]

Edit to above post.... the wig wag pot wiper will give forward and reverse...the speed limit pot can be altered for fast or slow.

pot wipers.jpg (41.73 KiB) Viewed 4182 times

[snoko]

Are there any restrictions with using this controller when it comes to batteries i.e. like LiFePO4 , and would it be possible to use dual motors ( 2 12v Cims ) or even a brushless ? ( Im assuming all these GOGOs use the typical brushed trannys ) ?

snok

[woodygb]

I've shown a controller that is suitable for a 24v brushed motor .. ANY type of batteries that total 24v upto 28v MAX ... and have sufficient Amp hr's will be fine.

How "fine" depends on the quality etc of the batteries you choose.

[snoko]

I've shown a controller that is suitable for a 24v brushed motor .. ANY type of batteries that total 24v upto 28v MAX ... and have sufficient Amp hr's will be fine.

How "fine" depends on the quality etc of the batteries you choose.

Is this open cycle when its in powered down state ?

I also noticed it mentioned something about having freewheel speed limit function which worries me as I was hoping I could use the throttle to coast .

snok

[woodygb]

the wig wag pot wiper will give forward and reverse...the speed limit pot can be altered for fast or slow

Hmmm ..PERHAPS THAT NEEDS QUALIFYING FURTHER.

The speed pot alters the throttle pots range ... so ..you set the speed pot and the wig wag throttles output would then be limited to this set speed.

[woodygb]

Is this open cycle when its in powered down state ? ( I noticed it mentioned something about having freewheel speed limit function )

Sorry Snok ....that statement makes no sense to me,.

[snoko]

Is this open cycle when its in powered down state ? ( I noticed it mentioned something about having freewheel speed limit function )

Sorry Snok ....that statement makes no sense to me,.

Hopefully thisshould explain it better than I can .

Thanks again for your all help.

snok

[Burgerman]

That page is talking about the controllers output stages, the bit that powers the motors, that switches the battery voltage when ON at high frequency.

We are talking about simple DC control voltages on the controllers input, a small signal, or command voltage, to tell the main controller controller what to do or what you want.

You dont need to know any of that. All you need to know is that if you feed the input +2.5v it goes full speed forwards. If you feed it -2.5v it goes full speed backwards. These are above and below a mid point reference voltage. At 0v it goes nowhere... And also subject to any programming. So maybe full reverse speed is 30 percent for eg. Or whatever you programed in.

[ex-Gooserider]

I've shown a controller that is suitable for a 24v brushed motor .. ANY type of batteries that total 24v upto 28v MAX ... and have sufficient Amp hr's will be fine.

How "fine" depends on the quality etc of the batteries you choose.

Is this open cycle when its in powered down state ?

I also noticed it mentioned something about having freewheel speed limit function which worries me as I was hoping I could use the throttle to coast .

snok

When the typical controller is turned on, it NEVER goes into a "powered down state", and it really doesn't coast - though the power draw goes pretty low at constant speed "cruise" - just enough power to overcome friction and rolling resistance losses. Otherwise, if you are travelling slower than the throttle setting, you will be drawing power trying to accelerate; and if you are travelling faster, the motor will act as a generator, slowing you down and slightly recharging the battery. (This is what you see referred to as "regenerative braking"

The only way to go to a Powered Down state is to shut the controller off entirely, however most will not do open circuit, as the designers of chairs and scooters see power loss as an "emergency condition" and will usually attempt regenerative braking and at the very least, it will allow the mechanical brake (primarily intended to keep you from rolling when stationary) to come on.

I'm not totally sure what you are wanting to do in regards to the speed control, but the way that the usual setup works is to have a joystick / wig-wag / twist-grip or other primary control that gives you direct speed control, and almost always has a sort of "deadman" function in that if you don't hold it constantly, if returns to zero. There is then a secondary control knob that sets the RANGE of the main control - essentially it limits your maximum speed, and it may give finer control of intermediate speeds when turned down...

ex-Gooserider

[woodygb]

Snoko,

Get down to your local mobility shop and test drive a scooter ..you should then be able to decide if the control system.... as is ..would suit your project.

A minor point ...B.M. Said that it's a 0v neutral with a 2.5v swing either side ...the Scooter controllers that I've come across are 2.5v neutral ...but have the same voltage swing.

Goose has managed to write a better description than I did..

the way that the usual setup works is to have a joystick / wig-wag / twist-grip or other primary control that gives you direct speed control, and almost always has a sort of "deadman" function in that if you don't hold it constantly, if returns to zero. There is then a secondary control knob that sets the RANGE of the main control - essentially it limits your maximum speed, and it may give finer control of intermediate speeds when turned down...

[Burgerman]

2.5v plus/minus and 0v centre compared to the reference voltage. Most joysticks, my rc adapter, the roboteq etc refer to it this way.

The reference voltage is of course 2.5v. With an actual swing of plus or minus considerably less than 2.5v as the rest is fault detection etc. On many devices/controllers its actually 1.3 or 1.5v plus/minus above/below reference for full 100 percent control. With some it can be whatever you choose and programming sorts out end points.

You get this reference voltage directly from many joysticks, as a means of fault detection, or error detection or accuracy. Although you dont need to use it. The roboteq allows you to use it, in absolute or relative input mode. Where "relative" uses this reference as the centre point. And absolute uses the 5v roboteq supply and takes 2.5v as the centre point. Which isnt as accurate since other things are also using the 5v. (LED warnings, RC rx, relay for brake etc. Although with a simple pot rather than a voltage controlled joystick either will work the same.

I tried to make this clearer but fear I failed!

[snoko]

I've shown a controller that is suitable for a 24v brushed motor .. ANY type of batteries that total 24v upto 28v MAX ... and have sufficient Amp hr's will be fine.

How "fine" depends on the quality etc of the batteries you choose.

Is this open cycle when its in powered down state ?

I also noticed it mentioned something about having freewheel speed limit function which worries me as I was hoping I could use the throttle to coast .

snok

When the typical controller is turned on, it NEVER goes into a "powered down state", and it really doesn't coast - though the power draw goes pretty low at constant speed "cruise" - just enough power to overcome friction and rolling resistance losses. Otherwise, if you are travelling slower than the throttle setting, you will be drawing power trying to accelerate; and if you are travelling faster, the motor will act as a generator, slowing you down and slightly recharging the battery. (This is what you see referred to as "regenerative braking"

The only way to go to a Powered Down state is to shut the controller off entirely, however most will not do open circuit, as the designers of chairs and scooters see power loss as an "emergency condition" and will usually attempt regenerative braking and at the very least, it will allow the mechanical brake (primarily intended to keep you from rolling when stationary) to come on.

Hi GR,

I should of remembered this for myself DUH ( I have been housebound 2 yrs so and not on scooter in about 3-4 ) , as the brake is right at the rear on my scooter it would need an emergency stop , I think ( because I only ever encountered it rolling back on buses ) I must of just assumed this would only work in reverse though ( which would be ok ) but not if I want overunning clutch I can use to coast ( for example down hills or slopes ) or if I needed to propel it myself ( if the battery went flat or I wanted exercise )

I'm not totally sure what you are wanting to do in regards to the speed control, but the way that the usual setup works is to have a joystick / wig-wag / twist-grip or other primary control that gives you direct speed control, and almost always has a sort of "deadman" function in that if you don't hold it constantly, if returns to zero. There is then a secondary control knob that sets the RANGE of the main control - essentially it limits your maximum speed, and it may give finer control of intermediate speeds when turned down...

ex-Gooserider

I think what BM said is probably the most accurate description ...
If he wants to use a rotary one for speed control (not to limit speed) then he can. And the trigger to over ride this, and one series diode would allow that.

Though im getting bit confused myself what the difference between speed control and speed limiter is ( aren't you controlling the speed by limiting the pot turns - / + any way ) ?

I think i thought I could use the pot / throttle in different combinations so I had more options rather than just being stuck say with option 1 but not the rest ....

I.E.

( option 1 ) - No hand gripping req

The pot was the speed control and no Throttle was used

( option 2 ) - Vice versa

( option 3 ) - Hand gripping needed

The pot was the limiter and the Throttle was the speed control

( option 4 ) - Vice versa

does that make sense ?

snok

[woodygb]

The throttle on mobility scooters is thumb operated , spring loaded and self centering ...this pic shows one ...you simply press the relevant end with your thumb for forward and reverse.

wig wag throttle.jpg (36.7 KiB) Viewed 3661 times

The speed limit pot is used to set a maximum speed range for the throttle.... note that this one has just 2 wires going to the wiper and one track end.

speed control.jpg (31.18 KiB) Viewed 3660 times

I assume that you would call this option 3?

[snoko]

The throttle on mobility scooters is thumb operated , spring loaded and self centering ...this pic shows one ...you simply press the relevant end with your thumb for forward and reverse.

wig wag throttle.jpg

The speed limit pot is used to set a maximum speed range for the throttle.... note that this one has just 2 wires going to the wiper and one track end.

speed control.jpg

I assume that you would call this option 3?

yup

Heres the one I got off ebay back at the end of 08 ( in good nic ) for under £400 , its throttle is a bit different the lever goes down and up - bit like a bike brake but far easier to push down or pull.

snok

[snoko]

The throttle on mobility scooters is thumb operated , spring loaded and self centering ...this pic shows one ...you simply press the relevant end with your thumb for forward and reverse.

wig wag throttle.jpg

The speed limit pot is used to set a maximum speed range for the throttle.... note that this one has just 2 wires going to the wiper and one track end.

speed control.jpg

I assume that you would call this option 3?

It was option 1 & 3 ( just to be clear ) I was really looking for .

Im assuming BMs diode method would mean option 1 & 2 . ( which would be ok too as an alternative option - but not my ideal choice )

snok