SW900 LCD

harrys

Pedelecer
Dec 1, 2016
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You UK guys might know more about this display. I have used KT controllers and know how to wire in a speed sensor. The controller that came with the SW900 doesn't have a separate connector for speedometer. It doesn't show the speed when coasting. Might be a setup issue, but I think it needs a sensor.

There might be an input on the controller circuit board, but I'd have to just guess and probe by trial/error. However, the docs for the SW900 says it has an extended function for speed sensor, as well as lights, etc, but I only have the typical 5 pin plug with power, Rxd, Txd, etc. I've googled and found a picture of the SW900 with an extra two pin connector, but no description.

Has anyone seen this display with an extra connector for a speed sensor? If so, then I'd open it up and look for the inputs.

P1650046.JPG
 
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Deleted member 4366

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If you don't have a speed sensor in your motor, you can fit an external one. The white wire in the controller hall sensor connector is the speed signal, so you have to pull it out of the connector (cut it).
 

harrys

Pedelecer
Dec 1, 2016
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Chicago, USA
If you don't have a speed sensor in your motor, you can fit an external one. The white wire in the controller hall sensor connector is the speed signal, so you have to pull it out of the connector (cut it).
That's true on KT controllers. Some have the white wire in the Hall connector and also a separate connector.

The controller for the SW900, which has neither of the above. I've seen some references on youtube where viewers ask how to connect the speed pickup, so I thinking it's part of the LCD. I'll have to open to the LCD and look,
 

Woosh

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viewers ask how to connect the speed pickup, so I thinking it's part of the LCD. I'll have to open to the LCD and look,
there is no speed pickup. The speed reading is encoded and sent by the controller to the LCD.
Do as d8veh says. If you can't find the speed signal wire on the controller, post a picture of the controller's wires here.
 
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Deleted member 4366

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That's true on KT controllers. Some have the white wire in the Hall connector and also a separate connector.

The controller for the SW900, which has neither of the above. I've seen some references on youtube where viewers ask how to connect the speed pickup, so I thinking it's part of the LCD. I'll have to open to the LCD and look,
Did you look to see if there's a white wire in the hall connector?
 

harrys

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Dec 1, 2016
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Chicago, USA
Post a pic? Sure.

The first is my parts box, working controllers but unused because they were either too low in power or too big in size. Not a newbie.

The second is the controller in question. I've tested it with every connector as labelled. The controller's Hall plug only has the 5 Hall wires, so I plugged in a Q100H motor to show the lonely white wire. Everything is spoken for, except speed.

Third/fourth are circuit board. There's an array of inputs in one corner on the 4th pic. One or two of them appear to have no wires connected. I may have to poke a speed signal and test ...after I ask the vendor if his factory can tell me.

controllers.jpg wires.jpg ckt1.jpg ckt2.jpg
 
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Deleted member 4366

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Sp looks promising. If it's not already used, solder a wire, then tap the other end on the 5v and ground to see if either gives a speed signal. Often, there's an LCD setting too, to tell the controller what to use for the signal.

I guess that controller was intended for a DD motor. They never tell you that when you buy them.
 

harrys

Pedelecer
Dec 1, 2016
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Chicago, USA
Could be SP. My eyes are too old to see what's on the controller unless I look at a picture. I'll hook up a speed sensor output and probe around.

The seller sells both DD and geared. Might be the same controller. I suppose many DD guys are on throttle 24/7. Gotta be boring.
 
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Deleted member 4366

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All the speed sensor does is provide a pulse. For testing, you can use a single wire, like I described above.
 

harrys

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Dec 1, 2016
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While I will everntually be using the motor that came with this kit, I already got the proper signal wire already coming out of my Q100H motor. Just gotta poke it around and see if the LCD responds. Will put a resistor on it.
 

harrys

Pedelecer
Dec 1, 2016
170
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69
Chicago, USA
Failed. I found 25 unused pads, split between 0V and 5V levels. as unable to produce a speed reading connecting a working speed sensor to any of them.

Oh well, my pack of inexpensive bike computers arrived in the mail today. They will always work,
 

I.A.N Tyler Durden

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Aug 22, 2017
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Hi I was wondering if the 2 extra wires on the sw900 was a speed sensor and found this thread and a another saying it was lights.
I connected the red and black to a 52v battery and the brown and white where putting out around 45v and when I turned the lights switch on it dropped to 11.75v. switching the lights off it returned to 38v .
Opening it up (lucky it was broken as it definitely is now) and the white wire goes to ground and the brown ro "deng".20200110_201205.jpg
 

harrys

Pedelecer
Dec 1, 2016
170
22
69
Chicago, USA
Late Update: Back in 2018, when I was searching for a speed input, I scoped out which pads had high voltage, but I still made a mistake and fried my Q100H speed sensor output by connecting it to 48V. So I connected up an imexpensive bike computer for speed,

However, while the controller and SW900 offered 5 level PAS, all PAS levels acted like PAS5 and quickly rushed me up to max speed. No ability to ride in any PAS level at lower speeds. What junk.

Those KT torque simulation units know how to do pedal assist. I switched to a KT with a 20A sine wave model and an LCD3.