Maker Pro
Maker Pro

How do I reduce the speed of a 12v childrens car

dave9

Mar 5, 2017
1,188
Joined
Mar 5, 2017
Messages
1,188
the pic i have just uploaded is of the control unit for the car

I see a silver blob with a label. You desperately need a better camera and to provide better pics. If we could have read the label we might have been able to figure out how the controller works.
 

73's de Edd

Aug 21, 2015
3,613
Joined
Aug 21, 2015
Messages
3,613
Sir surreyman . . . . . .

O.K. now . . . . . some more observations.

Addenda . . .
( Not now though, as you seem to show some out in left field controller . . . . did we not initially see that this unit has 12VDC power . . which must be three . . . . . ODD . . . . 4VDC cells in series)
Look at the spec plate on that unit as 42-48VDC and 35 amps and a whopping 1300 watts )

I thought what I have explained below was what you have, but just read and compare.

The very last photo that you posted, shows the rod that is mounted on top of the beam that reinforces battery mounting.

I merely see that mystical rod as pivoting up from the rear after being unclipped from the front, it then swings up to drop in a hole to support the hood / bonnet up.

Gadzooks . . . .nearby . . . .don't I even see hydraulic brakesused on that little puppy ?

Referencing to photo 2 of your posting, with your photo of the accelerator linkage being mostly blocked by the steering column rod and U- knuckle . . . I have marked up and filled in most of that area as shown below. *****

Here is what I see:
Phantomed in as silver, at the top center is the accellerator linkage, AS ACCELLERATOR LINKAGES ARE, it is spring loaded such as to have tension in the opposite direction of the top arrow.
Little GI Joe hops in and presses on the accelerator pedal which causes the opposite side of the linkages replication, extending down from the silver gland nut, to move in the opposite direction of travel .
Such direction as is marked with nearby yellow arrow.
The contact at RED STAR lets the A portion . . . .CARBON RESISTIVE CONTACT BLOCK . . . proportionally slide down inside separate telescopic part B.
There is encircling pressure electrical contact pressure engaging into the rectangular carbon block guesstimated within the ORANGE rectangle profile.
Initially the two A and B ends are electrically separated by a spacing, for no power flow, but after a slight movement towards each other, electrical contact is made at the highest resistive value of that carbon block to the B pressure contactor.
As the accellerator pedal is progressively pressed down, the telecopic action makes the resistance blocks length shorter . This produces lower resistance and higher motor speed.
The extreme limit will be when the GREEN X and X prime ( they are replicated on the other side towards the steering rod) bottom out and meet each other. Max speed is at that very low resistance setting.

INTERJECTION . . .

A Delmer Pee Dumbnuttzz type of simple solution would be to clean /scarrify/degrease the polycarbonate at point X and install a premeasured block of hardwood there to limit the X prime travel direction towards it and adhere with silicone rubber adhesive and do CURE WELL.
Of course one twin spacer block, is also being needed on either side.

Casper Pee Cloddd's more involved solution would be the use of longer screws at the RED star end of B and two washers that go against the polycarbonate block and cut out a rectangular metal bracket of 1.5--3 mm thickness that replicates that end quadrants width and has the central slot cut in it for the RED star dimension and then extends outwardly in the YELLOW arrow direction, in order to get enough length to fold over to make a right angle bend downwards and stop the end travel of the A portions protruding end.
Forming slotted holes in the bracket, at the added longer 2 screws + 2 washers + 2 star lock washers, let you then adjust the travel limiting bracket add on, to precisely 24.i44444786 KPH.

OBSERVATION . . .

Near the A block observe the use of doubled wiring for current capability and the trailing off routing direction with the RED dots.
The companion connection of the two ORANGE dots wires must go into the single B contactor assemblies black spiral accordion tubing being shown in its sole photo.



ASIDE . . .

In posting #29.
It doesn't seem to have any way of connecting to that 3-way plug/socket alongside.
Unless its just being used for size comparison, I believe that the 3 pin connector is being a red herring,and not being of any speed control association..

veet nam . . .VEET NAM ? . . . . . you should have come back with your fluent reply of

Trẻ em jeep điện. . ý bạn là bạn không biết gì về điều khiển động cơ điện tử của chúng.
Bạn đã làm cho xe kéo điện chạy không phải bạn?


What say ye now . . . .

*****
F8ZY254.png
. Please don't take my . . . . . . Kodachrome . . . .away . . . .
F8ZY254.png

upload_2018-9-19_15-15-9.png



73's de Edd
.....
 

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
hi, when i disconnect the resistor andput my voltmeter onto the wires i seem to get 2.42 ohms and when its connected up i get 3.49 volts that decreases to 0.847 volts when accelerator is pressed down. This is the controller C30T75A model- 48v/ 1200w- 75A -Undervoltage 42v- phase angle 120 degrees
 

Attachments

  • image1.JPG
    image1.JPG
    14.6 KB · Views: 13

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
Sir surreyman . . . . . .

O.K. now . . . . . some more observations.

Addenda . . .
( Not now though, as you seem to show some out in left field controller . . . . did we not initially see that this unit has 12VDC power . . which must be three . . . . . ODD . . . . 4VDC cells in series)
Look at the spec plate on that unit as 42-48VDC and 35 amps and a whopping 1300 watts )

I thought what I have explained below was what you have, but just read and compare.

The very last photo that you posted, shows the rod that is mounted on top of the beam that reinforces battery mounting.

I merely see that mystical rod as pivoting up from the rear after being unclipped from the front, it then swings up to drop in a hole to support the hood / bonnet up.

Gadzooks . . . .nearby . . . .don't I even see hydraulic brakesused on that little puppy ?

Referencing to photo 2 of your posting, with your photo of the accelerator linkage being mostly blocked by the steering column rod and U- knuckle . . . I have marked up and filled in most of that area as shown below. *****

Here is what I see:
Phantomed in as silver, at the top center is the accellerator linkage, AS ACCELLERATOR LINKAGES ARE, it is spring loaded such as to have tension in the opposite direction of the top arrow.
Little GI Joe hops in and presses on the accelerator pedal which causes the opposite side of the linkages replication, extending down from the silver gland nut, to move in the opposite direction of travel .
Such direction as is marked with nearby yellow arrow.
The contact at RED STAR lets the A portion . . . .CARBON RESISTIVE CONTACT BLOCK . . . proportionally slide down inside separate telescopic part B.
There is encircling pressure electrical contact pressure engaging into the rectangular carbon block guesstimated within the ORANGE rectangle profile.
Initially the two A and B ends are electrically separated by a spacing, for no power flow, but after a slight movement towards each other, electrical contact is made at the highest resistive value of that carbon block to the B pressure contactor.
As the accellerator pedal is progressively pressed down, the telecopic action makes the resistance blocks length shorter . This produces lower resistance and higher motor speed.
The extreme limit will be when the GREEN X and X prime ( they are replicated on the other side towards the steering rod) bottom out and meet each other. Max speed is at that very low resistance setting.

INTERJECTION . . .

A Delmer Pee Dumbnuttzz type of simple solution would be to clean /scarrify/degrease the polycarbonate at point X and install a premeasured block of hardwood there to limit the X prime travel direction towards it and adhere with silicone rubber adhesive and do CURE WELL.
Of course one twin spacer block, is also being needed on either side.

Casper Pee Cloddd's more involved solution would be the use of longer screws at the RED star end of B and two washers that go against the polycarbonate block and cut out a rectangular metal bracket of 1.5--3 mm thickness that replicates that end quadrants width and has the central slot cut in it for the RED star dimension and then extends outwardly in the YELLOW arrow direction, in order to get enough length to fold over to make a right angle bend downwards and stop the end travel of the A portions protruding end.
Forming slotted holes in the bracket, at the added longer 2 screws + 2 washers + 2 star lock washers, let you then adjust the travel limiting bracket add on, to precisely 24.i44444786 KPH.

OBSERVATION . . .

Near the A block observe the use of doubled wiring for current capability and the trailing off routing direction with the RED dots.
The companion connection of the two ORANGE dots wires must go into the single B contactor assemblies black spiral accordion tubing being shown in its sole photo.



ASIDE . . .

In posting #29.
It doesn't seem to have any way of connecting to that 3-way plug/socket alongside.
Unless its just being used for size comparison, I believe that the 3 pin connector is being a red herring,and not being of any speed control association..

veet nam . . .VEET NAM ? . . . . . you should have come back with your fluent reply of

Trẻ em jeep điện. . ý bạn là bạn không biết gì về điều khiển động cơ điện tử của chúng.
Bạn đã làm cho xe kéo điện chạy không phải bạn?


What say ye now . . . .

*****
F8ZY254.png
. Please don't take my . . . . . . Kodachrome . . . .away . . . .
F8ZY254.png

View attachment 43030



73's de Edd
.....

Yes that is exactly how the throttle resistor works- as the accelerator is pressed the two halfs come together and the length is shortened.
 

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
all the parts are supplied to the by this company in japan to the company in vietnam that assembles them - www.cq-motor.com - i have tried emailing but the dont reply- it seems they make small city delivery vehicles- seems like i have bought my young son something thats as powerful as a delivery vehicle ! not good ! it can currently scoot along at 25mph with 2 adults so totally unsafe as it weighs over 200kg.
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
andput my voltmeter onto the wires
Which wires?

There are three.

Show the voltages (with the wires CONNECTED) between:

red-yellow
red-green
yellow-green
yellow-red
green-yellow
green-red

As I stated, the throttle controller is a HALL EFFECT device - not resistive - so we need to adapt to a different method to limit the output. This may be as simple as a resistive divider across the output lines but that predicates we know which end of the throttle controller is 'ground'.
 

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
ok so been playing with the voltmeter- the is what i found- the pedal resistor has three wires (red yellow and green) and my voltmeter black and red- this is what i found in the various combinations (vm= voltmeter and r= resistor end-

1) red (vm) connected to red (r) plus black (vm) connected to yellow (r) = constant 4.35v

2) black (vm) connected to green (r) plus red (vm) connected to red (r)= +3.49v and reduces to 0.767v when accelerator fully depressed

3) black (vm) connected to yellow (r) plus red (vm) connected to green (r)= +0.867 and rises to 3.59v when accelerator fully depressed

So for the ohms side. i disconnected the pedal resistor from the controller and tested just the pedal resistor- findings were as follows-

1) red (vm) to red (r) plus black (vm) to yellow (r) = 2.42 ohms - did not change if i pressed accelerator

2) red (vm) to red (r) plus black (vm) to green (r) = no reading

3) red (vm) to green (r) plus black (vm) to green or yellow (r) = no reading

4) red (vm) to yellow (r) plus black (vm) to red (r) = 2.41 ohm

5) red (vm) to yellow (r) plus black (vm) to green (r) = no reading


sorry about all this - its a bit like guiding a plane down where the pilot cant fly! much appreciated though!
 

Ylli

Jun 19, 2018
401
Joined
Jun 19, 2018
Messages
401

Minder

Apr 24, 2015
3,478
Joined
Apr 24, 2015
Messages
3,478
From what I read of the controller it is a 120deg hall effect commutated BLDC motor with a variable control voltage of 1v to 4.2v.
It should be easy to tailor this 4.2 voltage to a lower level.
M.
 

Ylli

Jun 19, 2018
401
Joined
Jun 19, 2018
Messages
401
From what I read of the controller it is a 120deg hall effect commutated BLDC motor with a variable control voltage of 1v to 4.2v.
It should be easy to tailor this 4.2 voltage to a lower level.
M.
Yes, that is why I was looking for the resistance readings on the throttle 'pot'.
 

Alec_t

Jul 7, 2015
3,587
Joined
Jul 7, 2015
Messages
3,587
If a control voltage of 1-4V2 is used, I'm surprised that great lump of carbon is needed to adjust it. It does look robust though; which is no bad thing where kids are involved :).
 

73's de Edd

Aug 21, 2015
3,613
Joined
Aug 21, 2015
Messages
3,613
Hey Youse Guys . . . . .

To get this Chinese fire drill going in one direction . . . .isn't it about time to get a pic of the motor unit and see if it has just two wires coming out from it and the gauge of wire being used.
Or if there are three wires.
Or if this jeep might be dual powered if the . headlamps are stock auto headlamps, which could account for a 10-20 amp pull alone on a 12VDC battery.
If that motor controller photo is correct it should be on a short low loss run to the motor as well as the battery.

For that set of 3 cells for supplying 12VDC . . . . I could only see the use of that battery voltage and their current capability to power a DC motor and using that carbon block resistor / rheostat control method a la 1970's golf cart design.
(And golf carts use HUGE multiple 6VDC battery banks.)
I am wanting to think that those being seen in the jeep are sealed acid or gel cells . . .plus their weird 4 volts per . . .rating

The other situation is that there could be a BIG SEPARATE second power pack of Li Ion batteries to feed that controller, which would be feeding a 3 wire DC brushless motor .

Look at those specs ! on it It takes a lot of electrical power to haul 500 lbs of ass at 25 mph.
How about photos of the motor and controller wiring connects . . . plus . . . controller to battery wiring.

73's de Edd
.....
 

Minder

Apr 24, 2015
3,478
Joined
Apr 24, 2015
Messages
3,478
The controller itself states 48vdc 1200w and the typical scooter/bike models such as this has 5 conductors to the 3 hall sensors and 3 cables to the motor stator, the throttle voltage is typically 0.8v to 4.5vdc.
Typically not a 'block of carbon'
The internal processor also takes care of braking by using the motor commutation to do this.
M.
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
Yes, that is why I was looking for the resistance readings on the throttle 'pot'.
There IS no resistance on the throttle pot....... it's an active device, not a passive one.

The actual control voltage is the one that varies and appears on the GREEN wire with respect to the YELLOW wire if we accept the OP's tests as given..

Connecting a potential divider across the green/yellow wires and taking the output from the junction of the divider resistors and the yellow wire 'should' be enough to change the throttle control ratio.

The value of the two resistors is open for discussion.....
 

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
The controller itself states 48vdc 1200w and the typical scooter/bike models such as this has 5 conductors to the 3 hall sensors and 3 cables to the motor stator, the throttle voltage is typically 0.8v to 4.5vdc.
Typically not a 'block of carbon'
The internal processor also takes care of braking by using the motor commutation to do this.
M.
good morning- i retested with my voltmeter and got the same ohms reading at 2.38 but this time noticed it has a little 'k' by the 2.38 - i hope this explains things
 

Attachments

  • image1.JPG
    image1.JPG
    13.1 KB · Views: 17

BobK

Jan 5, 2010
7,682
Joined
Jan 5, 2010
Messages
7,682
The resistance measurement is of no interest. The thing you call a "variable resistor" is not a resistor at all. It is an electronic device that takes two power leads in and outputs a voltage dependent on the position of sliding pieces. That voltage is sent to the motor controller and determines the speed of the motor.

From your measurements, the wiring can be deduced to be:

yellow: ground
red: +4.35V
green: variable output

As @kellys_eye says, two resistors making a voltage divider can reduce the range of voltages output on the green wire and sent to the motor controller, which should limit the upper speed. Since it will also lower the lowest voltage out, it might mean there is added dead space when you start to push the accelerator pedal.

Bob
 

surreyman

Sep 18, 2018
20
Joined
Sep 18, 2018
Messages
20
The resistance measurement is of no interest. The thing you call a "variable resistor" is not a resistor at all. It is an electronic device that takes two power leads in and outputs a voltage dependent on the position of sliding pieces. That voltage is sent to the motor controller and determines the speed of the motor.

From your measurements, the wiring can be deduced to be:

yellow: ground
red: +4.35V
green: variable output

As @kellys_eye says, two resistors making a voltage divider can reduce the range of voltages output on the green wire and sent to the motor controller, which should limit the upper speed. Since it will also lower the lowest voltage out, it might mean there is added dead space when you start to push the accelerator pedal.

Bob
many thanks for that - you seem to make a lot of sense but i also put out a plea for help on another electronics forum. The chap on there just sent me this and i wonder whether you agree? here is what he said-

Now it makes sense, a factor of 1,000 times make a big difference!

This is what is needed:

The diagram is what you have now, the wiper (middle, arrowed) connection to the potentiometer picks off a proportion of the voltage from along the track (the box). As the pedal is pressed, it physically moves the wiper toward the top of the track where it picks up a higher proportion of the 4.35V and sends it down the green wire.

The bottom diagram shows the added potentiometer. Wiring the wiper to one end just makes it a variable resistor, the position of the wiper changes it's resistance from maximum (10K) to shorted out. Some of the 4.35V is dropped across the variable resistor, the amount depends on the resistance it is set to. If the new resistance is zero you are back to the original circuit, if set to maximum resistance, the green wire can't go above about 1V. Hence, it pre-sets the maximum voltage the pedal can produce.

The new control is easy to wire in, just break the existing red wire and connect it across the cut. Try to position it where it can't easily be reached or your son will soon work out how to beef things up again! The potentiometer you need can be very small, something like these:
https://www.ebay.co.uk/itm/3386F-1-t...VoshiI1S_Yoc9w
 

Attachments

  • image1.JPG
    image1.JPG
    8.9 KB · Views: 17
Top