Controller update for Yamaha XPC26

[Pedunculate]

I've been playing with my olde Yamaha XPC26 (24v NiMH battery, bottom bracket DC brushed motor, torque sensor). It has a fault where it'll run fine but if you stop pedalling for a few seconds it indicates a problem, giving two flashes on the LEDs. That's when it's freshly charged and the multimeter shows it has about 26.4v. Turning the PAS off and on again makes it work again. When I scope it the battery voltage is rock steady under load.

The controller is pretty simple, having inputs:

• 24V battery +/-
• 1K battery thermistor in series with thermal fuse (no markings on the fuse or that thermistor, but the charger side has a 103AT - appears to be 10K, beta=3435)
• Motor +/-
• Torque sensor: +5V/GND/torque, with idle at 0.8V, under torque gives up to about 1.5 V (I'm a little suspicious that the pedalling fault is related to this sensor)
• Handlebar unit (7 pins) - my guess is that's power switch (3 positions, 3 wires) and 3 LEDs (4 wires). It's possible the unit is cleverer than that, but I doubt it.

Unfortunately it's potted in silicone so it's not easy to see what's inside.

Under power (giving a steady voltage into the torque input rather than pedalling) it gives 24v PWM to the motor, with some filtering (ie cut the torque and it gradually ramps the power down over a few seconds)

I am pondering whether it's feasible to replace the controller with something more modern. What I'd like is a controller that can cope with the torque sensor and the DC motor. Since throttles also have a 0-5V output, I wonder if it's possible to use the torque sensor instead of/in addition to a throttle input.

What would be very nice is if it had a sensible gas gauge - for example, put a coulomb counter in the battery like a laptop, so it knows how much went in (via the external charger) and how much came out. I'm pretty sure the existing gauge is just looking at voltage. I'm happy to replace the handlebar controller with something more useful.

Will the common e-bike controllers handle this kind of thing? I see a lot of three-phase and 'torque simulation' controllers, but not sure if the brushed controllers will handle a real torque sensor.

 

[chrissybingbong]

I've been playing with my olde Yamaha XPC26 (24v NiMH battery, bottom bracket DC brushed motor, torque sensor). It has a fault where it'll run fine but if you stop pedalling for a few seconds it indicates a problem, giving two flashes on the LEDs. That's when it's freshly charged and the multimeter shows it has about 26.4v. Turning the PAS off and on again makes it work again. When I scope it the battery voltage is rock steady under load.

The controller is pretty simple, having inputs:

• 24V battery +/-
• 1K battery thermistor in series with thermal fuse (no markings on the fuse or that thermistor, but the charger side has a 103AT - appears to be 10K, beta=3435)
• Motor +/-
• Torque sensor: +5V/GND/torque, with idle at 0.8V, under torque gives up to about 1.5 V (I'm a little suspicious that the pedalling fault is related to this sensor)
• Handlebar unit (7 pins) - my guess is that's power switch (3 positions, 3 wires) and 3 LEDs (4 wires). It's possible the unit is cleverer than that, but I doubt it.

Unfortunately it's potted in silicone so it's not easy to see what's inside.

Under power (giving a steady voltage into the torque input rather than pedalling) it gives 24v PWM to the motor, with some filtering (ie cut the torque and it gradually ramps the power down over a few seconds)

I am pondering whether it's feasible to replace the controller with something more modern. What I'd like is a controller that can cope with the torque sensor and the DC motor. Since throttles also have a 0-5V output, I wonder if it's possible to use the torque sensor instead of/in addition to a throttle input.

What would be very nice is if it had a sensible gas gauge - for example, put a coulomb counter in the battery like a laptop, so it knows how much went in (via the external charger) and how much came out. I'm pretty sure the existing gauge is just looking at voltage. I'm happy to replace the handlebar controller with something more useful.

Will the common e-bike controllers handle this kind of thing? I see a lot of three-phase and 'torque simulation' controllers, but not sure if the brushed controllers will handle a real torque sensor.

Hi, i have the same bike and the same problem, i tried another 24v battery and the fault remained so it has to be the controller or possibly the torque sensor, ive phoned Holland and written too, but no joy as yet to finding the parts ! I'll post on here if I get lucky.

 

[Pedunculate]

Interesting. I have ordered a cheap eBay controller (seems like all the fancy ones are brushless, so cheap it is) and will have a go.

How many flashes do you get on the LEDs when it dies? I get a repeating sequence flash/flash/pause when I turn it on with the torque sensor disconnected. I don't remember how many it flashed when it was dying after about 8 miles.

 

[Pedunculate]

My Chinese controller (made by yiyun.cn) arrived courtesy of ebay. It turns out the battery and motor connectors are almost but not quite the same as the XPC26. After bodging them to connect, shorting the 'lock' pins, and applying a twist throttle to the 'derailleur' pins, it happily powered the XPC26 motor and wheel. Somewhat quieter than the original controller too.

I then turned my attention to the torque sensor. It's screwed into the side of the gearbox. It has an arm that pokes into the gearbox and presumably rotates to measure torque. I think mine is flaky: it records 8Kohm to ground at maximum travel, about 2.5Kohm at almost minimum travel, but then open circuit when under no pressure. It doesn't feel loose, but I'd guess the potentiometer track is worn.

It's labelled only 17Y0 or 17YO which wasn't the most helpful thing to google for, but then I came upon this thread on pedelecforum.de
That has some pictures of the inside, and indeed the track on that one is damaged. The page of the service manual shown there also confirms that flash-flash-pause means a problem with the pedal sensor (according to my German friend).

Also, they confirmed my suspicion that it's a motorcycle part of some sort. It seems to be a throttle position sensor (TPS) used on Yamaha motorbikes and other small engines (boats, snowmobiles). Googling around, it seems that unreliable TPSes are a known problem on Yamaha motorbikes. However they're frighteningly expensive (EUR200), for something that's just a potentiometer in a plastic case with a return spring.

Part number is 5AT-85887-10:


I did some poking around generic car TPSes (Chinese probably) which start at about £5, but I didn't manage to find anything that looks the right dimensions. One problem is that many have a connector moulded in the body, while the XPC has a part of the gearbox housing where that connector would go. Also it's unclear if the spring tension is carefully calibrated.

Otherwise it might require cracking open and trying to clean the potentiometer tracks. That could be the simplest option.

 

[djwlindenaar]

Hi guys,
sorry to dig up this oldish thread, but I'm in the same situation as you've been, so I'm wondering if there's been any progress on your end.

I've got the same bike (albeit branded by a dutch bike company named Sparta).
The torque sensor is there and indeed it looks like the potentiometer is worn. On mine there's infinite resistance at all terminals and when I power it, the sensor wire is either at 0 volts or at supply voltage. So it seems both the ground and sensor pins no longer make contact with the potentiometer tracks.

Anyway, Did any of you find a way to use an alternative part for the torque sensor since not only are these parts very expensive, but also hard to come by. At least in the Netherlands.

 

[Deleted member 4366]

What is the supply voltage?

 

[djwlindenaar]

The battery is at 24 volts (average, depending on charge levels) but the supply to the torque sensor is 5v.

Why do you ask?

Sent from my ONEPLUS A5000 using Tapatalk

 

[Deleted member 4366]

There's alternative torque sensors, like the Outrider OR05D1 that work off 5v, but you need to find a reseller. Maybe they would send a single one.

You could probably fit a normal throttle to your connector because they work at 5v. It depends on what the minimum voltages is required on the signal wire to start the motor. Throttles give 1.2 to 3.8v, so there's a small chance that the motor will run at zero throttle.

 

[djwlindenaar]

I'll have a look at the one you mention. I'm most worried about the mechanical interface to the torque sending linkage.

I've tested the electronics by hooking up a potentiometer, which works. I can check what the switch voltages are...

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