ku123 Speed Control with Three Speed Switch

[emiyata]

I am finishing wiring my 3 speed switch . After reading how to wire. It's not very clear. Here is what I understand black is the center of the switch and assume black is ground on the controller. blue goes to the other post to slow the motor for one speed. The other post has the red wire but they said it don't work. They said to get the next speed you short the 2 white wires and the black blue wires to get the lowest speed. To get isolation I would have to connect a pilot relay or a multi pole switch. After looking at the schematic the white wire is just connected to ground to enable its speed reduction but the drawing don't have the speed switch in it but I assume the blue is grounded to enable its speed reduction. My idea is to tie white and blue and go to the other post. Has anyone wired this switch this way? Is their any interaction between the white and blue wire connected together?

Thanks
Steve

 

[John in CR]

Try it the way you understand, because what they said makes no sense. Red does seem an odd color for a wire on a 3 speed switch. Check for a voltage on each first. Some 3 speeds come as 2 wires for a momentary switch, so blue to gnd could be 2nd speed and then blue to gnd again gives low. A vendor not understanding the equipment they sell for ebikes is extremely common.

 

[d8veh]

The three speed switch connector has a middle common wire (black) and two outer wires. One of the outer wires joined to the middle makes it go slower and the other faster. How much speed you get seems to be a lottery and can vary motor to motor and controller to controller, so, get your bike running first; then connect a speedometer to the back wheel. You only need to fit the magnet. You or a friend can hold the sensor in the right position for the speed test. Lift the back wheel (assuming rear drive) off the ground and open the throttle fully. Note the speed. Then, using a small piece of wire as a jumper, stick it in the middle and one outer; check the new speed; repeat for the other side outer. Now you know if you want to do anything with it. Sometimes you get 20% extra speed, which is useful if you have a slow motor. Let us know what you get because it's useful for others.

 

[emiyata]

Try it the way you understand, because what they said makes no sense. Red does seem an odd color for a wire on a 3 speed switch. Check for a voltage on each first. Some 3 speeds come as 2 wires for a momentary switch, so blue to gnd could be 2nd speed and then blue to gnd again gives low. A vendor not understanding the equipment they sell for ebikes is extremely common.

Thanks John for your input. I didn't want to reinvent the 3 speed switch. :lol: I don't think this is the case. This switch looks like a toggle switch with center off. I still have to finish building a removable battery box and when I finish with that I will connect the optical tachometer and multimeter and hopefully figure this thing out. I will need to be careful like you said not to burn a trace off the board by taking 5v to ground.
If I can figure this thing out I will post my 3 speed switch setup.

 

[emiyata]

The three speed switch connector has a middle common wire (black) and two outer wires. One of the outer wires joined to the middle makes it go slower and the other faster. How much speed you get seems to be a lottery and can vary motor to motor and controller to controller, so, get your bike running first; then connect a speedometer to the back wheel. You only need to fit the magnet. You or a friend can hold the sensor in the right position for the speed test. Lift the back wheel (assuming rear drive) off the ground and open the throttle fully. Note the speed. Then, using a small piece of wire as a jumper, stick it in the middle and one outer; check the new speed; repeat for the other side outer. Now you know if you want to do anything with it. Sometimes you get 20% extra speed, which is useful if you have a slow motor. Let us know what you get because it's useful for others.

I will connect a tachometer to it. I will see what I get. I hope its just a switch in the resistor network for the throttle. I could take it apart and draw a schematic of the 3 speed switch. I do need to be careful I don't want to damage the controller and have to repair the controller or order one from China. Like I told John I will post my findings.

 

[emiyata]

I have the pinout of the the 3 speed switch from BMS battery.

Blue (left side of rocker pressed)
Red (Common)
Black (right side of rocker pressed)
-
Note: (Center is the off or no connection to blue or black )

 

[d8veh]

I have the pinout of the the 3 speed switch from BMS battery.

Blue (left side of rocker pressed)
Red (Common)
Black (right side of rocker pressed)
-
Note: (Center is the off or no connection to blue or black )

They've changed it then. It used to be black common, blue low-speed and green high-speed on the KU123, and on KU63, the blue and green were reversed - probably not standardised.

I hope their above recommendation is correct. If you don't get any change with red and blue connected, you might want to try it with black as the common. It's nearly universal on Chinese controllers that black is 0v. The previous version KU123 had green or blue wire shorted to earth so that they were pulled down to effect the change, so, assuming red is 5v (normal standard), it wouldn't make sense to have earth one side pulling it down, and something sent high the other side. It's possible, but seems strange logic.

 

[emiyata]

I have the pinout of the the 3 speed switch from BMS battery.

Blue (left side of rocker pressed)
Red (Common)
Black (right side of rocker pressed)
-
Note: (Center is the off or no connection to blue or black )

They've changed it then. It used to be black common, blue low-speed and green high-speed on the KU123, and on KU63, the blue and green were reversed - probably not standardised.

I hope their above recommendation is correct. If you don't get any change with red and blue connected, you might want to try it with black as the common. It's nearly universal on Chinese controllers that black is 0v. The previous version KU123 had green or blue wire shorted to earth so that they were pulled down to effect the change, so, assuming red is 5v (normal standard), it wouldn't make sense to have earth one side pulling it down, and something sent high the other side. It's possible, but seems strange logic.

This is the switch colors not the controller. The colors you said are for the controller end.

 

[d8veh]

This is the switch colors not the controller. The colors you said are for the controller end.

I see. You can test the switch with a meter that beeps (continuity) to confirm. For testing, I always use a bit of wire to bridge the controller directly. No doubt then. If there's not additional speed in the high position, I remove the wires and connector from the controller and chuck the switch, If there's a gain and I'm happy with the speed, I cut off the connector and solder the wires.

 

[emiyata]

I cut off the connector and solder the wires.

I think I will be useful . Making it work in the range I need maybe another story. The drawing online shows that the 20 mph jumper (white wire) just places another resistor in the throttle resistor network,so if this switch don't work well, I will look into maybe using the white wire. The first step is seeing what the stock switch will do. Thanks for the help.

 

[mlt34]

This is the switch colors not the controller. The colors you said are for the controller end.

Oooooooooh that was the switch color scheme, now I get it. I was super confused. I've had a lot of KU123s in my hands and I've never ever seen a 3spd switch connector with red blue and black.

 

[mlt34]

Also, what are you trying to accomplish? Do you want the option to switch speeds on-the-go, or are you just looking to permanently increase or decrease the speed once-and-for-all? If it's the latter, like dv said, just bridge the connector on the controller to find the right combo, then solder those wires together. I just use a piece of solder for bridging the connector pins when I'm testing for the right combo.

 

[emiyata]

Also, what are you trying to accomplish? Do you want the option to switch speeds on-the-go, or are you just looking to permanently increase or decrease the speed once-and-for-all? If it's the latter, like dv said, just bridge the connector on the controller to find the right combo, then solder those wires together. I just use a piece of solder for bridging the connector pins when I'm testing for the right combo.

I want full speed 25mph ,20mph ,15mph. The PAS will turn on the power and go to the selected speed. I know this would be ideal but it may need some mod's in the box. It would be nice to have a controller that is broken so I can trace the circuit and see how they designed it. In time I may order a spare to trace the circuit. It's a bit disappointing that that this function may not work well. On the other hand for $25 just how much do you expect from the controller.
Thanks for the great input.
Steve

 

[d8veh]

From memory, the three-speed switch has no effect on PAS. It only works with throttle. Instead, the speed you get with PAS is cadence related. The faster you pedal, the more power you get up to a point. It sounds sort of logical. but in practice, it makes the bike impossible to ride. You'll know what I mean when you try it. If you want to use PAS with the KU123, you need an independent device that can detect pedalling from the PAS sensor, and translate output to a throttle signal that can be varied, otherwise you need a different controller like those offered by Conhismotor with LCD display.

 

[emiyata]

From memory, the three-speed switch has no effect on PAS. It only works with throttle. Instead, the speed you get with PAS is cadence related. The faster you pedal, the more power you get up to a point. It sounds sort of logical. but in practice, it makes the bike impossible to ride. You'll know what I mean when you try it. If you want to use PAS with the KU123, you need an independent device that can detect pedalling from the PAS sensor, and translate output to a throttle signal that can be varied, otherwise you need a different controller like those offered by Conhismotor with LCD display.

Thanks for the input. I will have to play with it when the bike is done. I am building a battery box now and hope to power the bike this next weekend. The weather has been very cold , so testing it on the road may not happen with the ice we have and 20 degree weather. The CA I am building will use the Thun sensor, so I think in time I will use that on the bike.

 

[emiyata]

I have the battery box built and had the tire spinning. I now have to clean up the wiring and give the bike a test ride Monday and test the PAS. If all goes well this weekend I want to get the tachometer and test the three way switch and post the numbers. The weather is still bad here. We have snow and 30 degrees. Hopefully Monday it will be nice and get the bike out.

 

[emiyata]

Well I hooked the gauge to read speed of the unloaded tire with the 3 speed switch. I have the 393 rpm motor BPM II 500w 48v with 24" tire.

Low speed = 24.5 MPH
Med speed = 31.3 MPH
High speed = 32.5 MPH

Note this is unloaded speed.

 

[mlt34]

Well I hooked the gauge to read speed of the unloaded tire with the 3 speed switch. I have the 393 rpm motor BPM II 500w 48v with 24" tire.

Low speed = 24.5 MPH
Med speed = 31.3 MPH
High speed = 32.5 MPH

Note this is unloaded speed.

I wonder if you will see any change in speed 2 and 3 when you're actually riding. Let us know!

 

[emiyata]

I wonder if you will see any change in speed 2 and 3 when you're actually riding. Let us know!

Yes you can tell the speed change but from medium to high not much and you can hear a higher pitch sound from the motor.