# Ct-312c1



## MACvolt (Jul 28, 2014)

Hi folks,

I'm looking to "improve" my grandsons MX650 and I'm interested in the controller module.

Part number is CT-312C1 and I'd like to know the principle of operation, PWM, simple resistor switching etc.

If anyone has a schematic of the controller it would be very helpful.

Thanks folks.


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## RIPPERTON (Jan 26, 2010)

How about some photos.
Assuming the Razor 650 is lead acid to brushed DC motor.
The controller is probably a cheap mosfet unit.
You could get twice the performance with some lithium and Kelly ctlr.
Dan


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## MACvolt (Jul 28, 2014)

RIPPERTON said:


> How about some photos.
> Assuming the Razor 650 is lead acid to brushed DC motor.
> The controller is probably a cheap mosfet unit.
> You could get twice the performance with some lithium and Kelly ctlr.
> Dan


Thanks for the response.
Don't have pics at present because grandson lives some distance away.

The batteries are sealed lead/acid and I assume the motor is a brush type.

Looking at the overall schematic, I'm guessing the controller is switching in different resistors via Mosfets for the different speeds so it's really a torque control, but that's why I'd like to see a schematic that shows what's inside it.

I'm thinking a true PWM would not only give a wider speed range but also be a lot more efficient.

I assume the Kelly controller you suggest uses that principle?


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## RIPPERTON (Jan 26, 2010)

http://kellycontroller.com/kds72050e50a24v-72v-mini-brushed-controller-p-760.html

This 50A ctlr is a bit bigger than a playing card but can be configured with a free downloaded program and an rs232 to usb cable.
You can go to 80v with this for 4 times the speed/rpm.
Im sure your grandson could relate to that. 

what voltage is the Razors Lead acids ?


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## RIPPERTON (Jan 26, 2010)

http://www.razor.com/products/electric-ride-ons/mx650/

They are 36v so you would only double your speed going to 80v
but not all is lost, with the extra current you go to a taller gearing for at least 50kmh.


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## MACvolt (Jul 28, 2014)

RIPPERTON said:


> http://www.razor.com/products/electric-ride-ons/mx650/
> 
> They are 36v so you would only double your speed going to 80v
> but not all is lost, with the extra current you go to a taller gearing for at least 50kmh.


Appreciate your input, but wouldn't doubling the voltage quadruple the power (watts)? So is that's what required for a doubling of speed?

I'm also concerned about over-revving the motor, any idea what's the max rpm of that type of motor? Wouldn't want to have an armature explode.

I appreciate the tuning suggestions and will look into them, but I'm still curious as to what principle that controller operates on and would dearly like to see a schematic.


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## RIPPERTON (Jan 26, 2010)

Double the volts doubles the speed and Wattage
volts times amps is Watts.
http://www.electricscooterparts.com/hookup/CT-312C1-3.htm
Heres the standard MX650 ctlr
36v times 30 amps is 1080 Watts.
go to the Kelly with 80v times 50A = 4000Watts.
The motor in the MX650 would be over rated for the 650-1000 Watts its getting so would go for a while on 4kW or you could turn the Kelly down to 50% power just to see how hot the motor gets.
Your dabbling in mad science now, be prepared to blow shit up.


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## fixitsan (Jul 9, 2014)

Thats a PWM controller.
It doesn't switch resistors like an old school controller would do (imagine the size of 650W resistors !) , but instead it pulses the voltage on and off to control average motor current.

Imagine pressing a buttonat 100 times per second, and when the button makes the circuit to the motor you control how long the button stays in the made position. if you are only briefly 'blipping' the button then it will be on for a very short amount of time, say 1 millisecond. Repeat that action 100 times per second at regular intervals and you will produce a force in the motor's magnetics enough to turn it slowly.

Now instead of keeping the button pressed for 1ms, you keep it pressed for 2ms each time....the motor turns more quickly.

And so on. PWM = pulse width modulation.

Electronics in the controller sends signals to silicon devices, usually mosfets, but in cheaper controlelrs large bipolar transistors (and in very old PWM controllers, triacs/SCR's) to cause them to switch the current on and off.

PWM controllers are the source of the whining or whistling sound, which is related to the frequency at which the current is switched.

A 100Hz switching frequency in my example above is quite slow by today's standards....400Hz is more common, 5kHz is better, and many these days run up near or above 20kHz (hence the high frequency whine you sometimes hear)



I looked at that controller and saw how small it was. It is possible that they have used good quality mosfet transistors, but my experience of mass produced cheap foreign electronics is that they are made with whatever is cheapest. A 'good quality' mosfet can in this case be described as one which has very low 'on-resistance'.

When the mosfet switches the motor's current it has a small internal resistance of it's own. A poor quality mosfet might have an on resistance of 0.1 Ohms. Because power dissipation is related I^2 x R then if the device is passing 20 Amps of current then the power wasted in the device is 20 x 20 x 0.1 = 40W ! Thats a lot of power to waste, and a lot of heat to dissipate.

A top quality mosfet might have an on resistance (Rds) of 0.01 Ohms or less, so you can see that you will only lose 4W of power in the controller in this case (20 x 20 x 0.01 = 4)


In terms of choosing a controller it is better sometimes to go at it in terms of of it's specifications. What is it's Rds ? (on resistance), what frequency does it operate at (higher is often better, except when just getting going) , do the wires look like they can carry the amount of current you hope the controller will pass ? Many of the cheaper electronics use wires which can barely cope.....in turn those thin wires add to the overall resistance of the controller circuit and ruin the efficiency.

A higher voltage is good, because you tend to use less current to make the same power (from P=IV) so thinner wires and a lossy controller don't matter as much, but instead the voltage rating of the wire's insulation and any relays/contactors used does matter there....and bear in mind that fuses have a voltage rating too, so be prepared to at least check those !


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## MACvolt (Jul 28, 2014)

fixitsan said:


> Thats a PWM controller.
> It doesn't switch resistors like an old school controller would do (imagine the size of 650W resistors !) , but instead it pulses the voltage on and off to control average motor current.
> 
> Imagine pressing a buttonat 100 times per second, and when the button makes the circuit to the motor you control how long the button stays in the made position. if you are only briefly 'blipping' the button then it will be on for a very short amount of time, say 1 millisecond. Repeat that action 100 times per second at regular intervals and you will produce a force in the motor's magnetics enough to turn it slowly.
> ...


Thank you for your input, much appreciated.

So it is a PWM controller, but is the pulse repetition frequency (PRF) fixed or variable?

Any idea as to what the frequency is or the range of frequencies if variable?

As you point out, the Rds (on) parameter is the main one but the total power dissipation (Ptot) has to be considered, particularly at higher switching frequencies, since most power loss occurs in a Mosfet during the transition times from full on to full off.

Coupled with that of course is its switching frequency, mainly determined by its transition times from full on to full off and that too ties into the drive capability of the control circuitry.

That being said, I'd expect the PRF to be fairly low in order to utilize low cost Mosfet's and because it's feeding an inductive load, i.e. the motor.

Higher voltages make a lot of sense, especially with larger vehicles, but high voltage and low Rds (on) parameters don't come cheap with Mosfet's so is there a controller currently available that uses Igbt's?


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## fixitsan (Jul 9, 2014)

The frequency i couldn't tell you, not without measuring it or getting a spec sheet - why not write to the manufacturer and then you'll know for sure. 

I was under the impression that because you were working with such a small and cheap bike that you wouldn't throw large sums at it - there are IGBT controllers, how much do you want to pay ? 

If you can do it yourself, then have a look at the Open Revolt, uses lots of cheap mosfets, and is a good design overall http://www.paulandsabrinasevstuff.com/evmotorcontrollers.html


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## MACvolt (Jul 28, 2014)

fixitsan said:


> The frequency i couldn't tell you, not without measuring it or getting a spec sheet - why not write to the manufacturer and then you'll know for sure.
> 
> I was under the impression that because you were working with such a small and cheap bike that you wouldn't throw large sums at it - there are IGBT controllers, how much do you want to pay ?
> 
> If you can do it yourself, then have a look at the Open Revolt, uses lots of cheap mosfets, and is a good design overall http://www.paulandsabrinasevstuff.com/evmotorcontrollers.html


My original request was for a schematic and/or specifications for the MX650 bike's controller with the thought of seeing how far I could push it without having to redesign or build my own, and in that regards I'd still appreciate that information.

I suspect the manufacturers would be reluctant to impart that information, I know I would be.

My comment about Igbt's was in regards to larger higher voltage vehicles and was simple curiosity with no thought or intent of using them.

Thanks again for your input.


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## fixitsan (Jul 9, 2014)

No problem.

Have you opened it up and looked at it ? Drawing the schematic from the pcb should be fairly simple. Thy're only motor controllers so not really rocket science.

It will contain an oscillator/generator/logic circuit, the switching device, possible with it's own driver chip, and if it's sophisticated enough some current measuring for feedback, but I doubt that would be in that device, they probably rely on the mosfet's tendency to restrict it's own current as it heats up.

My question then would be what are you trying to do ? If you want to run a higher voltage then just check the mosfet part number with the manufacturer to see if it can take the increase. The logic circuit would probably need some consideration, if it is supplied via a voltage regulator then yiou might have to change that for a higher spec device, and check any feedback, reference voltage for consistency, but in theory it's quite simple.

But then again, if you're going to spend a few hours doing that, and then maybe start tinkering and spend more time and money doing that....why not just throw 60 bucks at the higher spec devices and spend more time having fun instead ?


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## MACvolt (Jul 28, 2014)

fixitsan said:


> No problem.
> 
> Have you opened it up and looked at it ? Drawing the schematic from the pcb should be fairly simple. Thy're only motor controllers so not really rocket science.
> 
> ...


As previously mentioned, the bike is some distance from myself so opportunities to open it up and investigate are limited, but even so, I'm reasonably certain the control board will be using surface mount components and at least double layer circuit boards which make circuit tracing virtually impossible.

Maybe, just maybe, the Mosfet part number's will be visible since they're likely to be mounted to a heat sink but even that's not for sure.

BTW, a Mosfet can limit current by increasing the Rds on and Vgs threshold voltage, neither of which are good in a switching circuit.


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## fixitsan (Jul 9, 2014)

MACvolt said:


> BTW, a Mosfet can limit current by increasing the Rds on and Vgs threshold voltage, neither of which are good in a switching circuit.


Yes, true, but I think what I was meaning was that you are unlikely to see just one mosfet doing all the work in a 650W controller, instead two or more are often connected in parallel. With BJT's that can be a problem because the strongest transistor does most of the work, gets hot and then burns. But that is not what happens with mosfets, when they get hot they effectively throttle back the amount of current which they can pass so they balance the current in the circuit between themselves.

If the motor is bipolar, then you'll see a simple arangement of the mosfet (or paralleled group of mosfets) switching either the high or low side. If the motor is 3-phase you'll have three switching channels, almost certainly controlled by a bespoke 3-phase motor controller chip (synchronous likely) , of which there are many on the market these days.

Motorolla make a load of similar 3-phase PM motor controllers, and they document them very well. Do not be at all surprised if you find that the circuit in your controller is just an example circuit of the chip makers datasheet. You'll soon know by comparing the values of a few significant resistors and capacitors with the datsheet and app note.

EG http://www.freescale.com/files/microcontrollers/doc/ref_manual/DRM029.pdf?fpsp=1


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## RIPPERTON (Jan 26, 2010)

Looks like you could get away with a very cheap mod MAC, just add another battery in series for 48v and 35% power increase.
http://forum.modifiedelectricscooters.com/viewtopic.php?f=10&t=842
apparently the MX650 ctlr can handle up to 60v.
Then you have to get a bigger charger of course.
http://tncscooters.com/index.php?route=product/product&path=17_77&product_id=71

The beauty of this is you get to teach your GS all about Electrical engineering in a fun way.


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## MACvolt (Jul 28, 2014)

RIPPERTON said:


> Looks like you could get away with a very cheap mod MAC, just add another battery in series for 48v and 35% power increase.
> http://forum.modifiedelectricscooters.com/viewtopic.php?f=10&t=842
> apparently the MX650 ctlr can handle up to 60v.
> Then you have to get a bigger charger of course.
> ...


That's great information, just what I was looking for and saves me the legwork of researching it, thank you!

BTW, as an old EE I don't hold out any hope of teaching GS about electrical engineering since I couldn't manage it with my Son, he wimped out and went into computer networking security.


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