KT-LCD3 Button Question/Help

SiiXFX

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Feb 18, 2018
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Hello! I'm building a E-Bike with a 1500W motor. I'm from Germany and here it's only allowed to drive 25km/h with a E-Bike.. :?
Now I saw something on YouTube.. a guy connected a button to the KT-LCD3 Display. So you can drive full speed but when you press the button you can only drive 25km/h. Does anyone know how he could have done that?

I could only take a picture of a video. You can not see more from this button. :(

Zcx5mbH.png


It looks like the button is between the cable from the controller to the display. But how is it possible to set a 25km/h limit with this button? Thanks in advance! :)
 
What does the guy that made the video say when you ask? (or is he unwilling to discuss it?)


Most likely he is using a setting in the system itself to give two modes, and the button just chooses between them.
 
On questions about the button, he refers to his e-mail, but apparently he no longer responds to e-mails. :?

In the videos he said, that if you press the button the display turns off but you can still drive. (25km/h)
If you press the button again, the display turns on again, but it's still locked at 25km/h.

He didn't said anything about how to undo it. But that's not the question now.. :lol:

If you think you know how he does that, maybe you can help me? I have no idea about it. :?

Edit:
Because as it looks in the picture, it's just a button between the controller and the display. How can you change profiles with this? And how can you do it permanently? So that one another press the lock persists. Sorry for my bad english by the way.. :roll:
 
SiiXFX said:
In the videos he said, that if you press the button the display turns off but you can still drive. (25km/h)
If you press the button again, the display turns on again, but it's still locked at 25km/h.

Ah, if that's what he's doing, then it means the LCD is setup to limit speed, but that the controller without the LCD is not.

So what he's done is put a connector between the LCD and the controller that does two things.

It has a wire that shorts the "keyswitch" wires on the controller side of the connector to keep the controller on whether the LCD is on or not. (normally the LCD controls this).

It puts the switch (SPST latching on/off, can be pushbutton or toggle) wired in series with the battery voltage from the controller side of the connector to the LCD side of the connector.

When you turn the switch on, eveyrthing works normally, however you ahve setup the LCD.

WHen you turn the switch off, everything works however the controller is programmed to operate.


The only catch is you may have to first turn off power to the whole bike before changing modes, to reset the controller to defaults.

SiiXFX said:
On questions about the button, he refers to his e-mail, but apparently he no longer responds to e-mails.
Maybe he got arrested for exceeding the speed limit? ;)
 
Oh wow, thank you for the reply! :)

So with this "setup" you described you can only drive 25km/h once the button is pushed (on position)?
And if you press the button again (off position) you can only drive 25km/h too?

Or do you mean, when you press the button (display off) = no limit
and when you press it again (display on) = 25km/h limit

Because when he pressed the button once, than it doesn't matter if the display is on or not. He still had a 25km/h limit.

Thank you very much for you help!

Edit:
Or maybe I got it wrong from the video, and it's just as you described. :lol:
 
SiiXFX said:
So with this "setup" you described you can only drive 25km/h once the button is pushed (on position)?
And if you press the button again (off position) you can only drive 25km/h too?

Or do you mean, when you press the button (display off) = no limit
and when you press it again (display on) = 25km/h limit

Because when he pressed the button once, than it doesn't matter if the display is on or not. He still had a 25km/h limit.
Keep in mind that I'm guessing based solely on what you tell me about the system, since I have no way of knowing what his system (or yours) actually do, or what happens in the video except for what you tell me.

That said, what happens when the switch is changed depends on how the controller and LCD work.

If the controller depends on the LCD to do the limiting, then with the LCD off, no limiting will happen.

If all the LCD does is tell the controller what it's own limits are, then the controller does everything and the LCD just displays what the controller tells it to, and the LCD with it's built-in buttons tells the controller what settings you've changed, and the controller rmemebers those whether or not hte LCD is there.


Basically the only connection between LCD and controller in the KT series is Battery Postive and NEgative, provided by the controller to the LCD all the time the bike is on. THen there is a return battery postiive wire provided by the LCD to the controller, used by the LCD to switch the controller fully on whenever you use the LCD's built-in power button. Then there's two wires used by LCD and controller to send data back and forth, which can include the LCD telling the controller what it's limited to, and the controller telling th LCD what to display.


Theres' a lot of threads about the KT (kunteng kun teng) controllers and LCDs, if you want to look around the forum for them; maybe one of them has more info that is specific to your problem.


There is one more thing you can switch on or off that will disable any speed limits: The system has a speed sensor, and if that isn't connected, then the controller has no idea what speed it is at, so it can't limit it.

If the speed sensor is a separate sensor on the frame driven by a magnet on the spokes, then it's really easy to disable--just put the switch in series with either wire from the sensor.

If the speed sensor is in the motor, and has a separate wire for that, put the switch in that.

If the speed sensor is in the motor and uses one of the hall sensor wires for it, then unless your controller can run sensorless, then you can't switch this one off. The controller needs it to know how to spin the motor.

The catch with any of these is that the system may have a timer in it that if it doesn't get a speed signal within a few minutes, it powers off the bike thinking it's not being used. There may be a setting in the LCD to turn that off on some of them; you'd have to check the manual for yours to see.

But as long as you turn the switch back on to enable the speed sensor every so often, before it shuts the system off, then turn it back off again, it'd reset the timer.
 
Several things I recall reading about the KT-controller interface to the LCD.

1) You can run without the display if you connect the TXD and RXD leads together and connect the Batt voltage to the start wire. The controller defaults to some slower speed.

2) Someone posted that if you plug the LCD back in while the above is done, you can monitor all the info sent by the controller but you cannot change anything. I presume you can see the speed, watts, etc.

I think one could wire up a switch to do the above. First you switch off the LCD3. Now throw the switch so the controller powers up in slow mode. Finally turn on the LCD3 again. The OP should be able to figure out the wiring. It will need to leave the LCD3 connected to the serial data input when switched.
 
Thanks for that wiring information I might try this mod with a kt 11A-22A controller and the lcd5 display.
 
Thank you @docw009!

Would be cool if you test it and post your results here. I can't test it atm because I need to build my battery first..

I also got another idea. I maybe missed a spot in the video. He said he has 2 displays. One slowly trimmed (25km/h) and one fast trimmed (full speed). Maybe he can switch the display with this button? But if it's pressed once, the controller only use the slow display until you change the display manually or something like that?
 
Found it very problematic. I could start the controller just by jumpering the start wires. Didn't need to cross Rxd and Txd. As I wasn't running the motor under load, just had it on the bench, I couldn't tell the rpm.

Sometimes it seemed like it was running at some default speed as advertised in the manual. Other times it seemed to be spinning up very fast. Never could get the LCD3 to display speed when the transmit/receive lines were opened up.

Well, I was just twisting wires together, and not following a specific powerup sequence, so maybe that has to be done.
 
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