Any way at all to add a throttle to a Trans-X setup?

[shambolic]

Hi after having my A2B Metro stolen I went and bought an Ebco Eagle which has a Trans-X PST, trouble is because of my Neurological condition my legs become too weak to pedal after a while. As I would lose a lot of money if I sold it on I am wondering if there is any way at all to add a throttle to this bike? Any idea at all how I could do this. This system works with some kind of pressure sensor.

 

[ecycler]

I am not familiar with their setup, but it should not be hard if it is similar to other PAS systems. Where are you located?

 

[shambolic]

Hi, I'm in the UK. This is the model:

http://electricbikesdirect.com.au/products/ebco-eagle-lifestyle-lsr-50-electric-bike

Some people are telling me because it is pressure based this can't be done. I'm not so technically knowledgeable so am fishing around for info. The bike really suits me apart from this big problem, it's low centre of gravity which I find much easier and rides in a very stable fashion. I bought a 26" bike and kept falling off every time I hit a rough patch.the A2b suited me great but was a little heavy.

"Powered by the Transx PST electric drive system which features a 250W 36V high torque electric front hub motor matched to an RPM and intelligent TMM4 torque sensor - the result is smooth, intuitive electric assistance and a superb riding experience."

 

[ecycler]

Looks like a cool bike. Can you take some close up pictures of the controller? Do you have any electronics experience?

 

[shambolic]

Looks like I have to take some parts off to get to the controller. I may be a few days as I'll need someone to help on this.

 

[ecycler]

Takes some pictures of the PAS sensor and wiring as well while you are at it, please. Do you have a multimeter?

 

[teklektik]

Don't bother taking things apart. Pointless.

A few minutes with Google shows your bike uses two sensors: RPM and torque - not unusual.

Electric Drive System

• Motor = TranzX PST 250W 36V brushless high torque front hub motor
• Sensor = Intelligent TMM4 torque sensor matched to an RPM sensor

These outputs are typically going to be combined to determine the human power input (torque x rpm = power) which will be applied and scaled into assist by some proprietary algorithm.

A. The rpm sensor can only be one of two simple types using either one or two halls - I'm guessing two so the controller can detect backward pedaling. This could be faked without too much difficulty with a bit of electronics.

B. The torque sensor is a TMM4:

TMM4 torque sensor - http://www.idbike.com/index.php/sensors

• TMM Sensor Unit (hall-based)
  • Supply voltage: 5 V
  • Output voltage: 1 V- 4 V

So - to trick the controller into working entirely from a throttle you will need to generate these two signals (rpm + torque). This is certainly doable, but not an off-the-shelf solution.

The best you might try for a quick fix is to replace the torque sensor with a standard hall throttle. The torque sensor spec shows this to be the familiar 3-wire 5V power 1V-4V signal as with any common hall throttle. This would let you fake the pedal effort with the throttle but you would still need to at least faux-pedal to activate the PAS algorithm. This might be workable - you wouldn't need to exert any force, just keep up the cadence and adjust the fake 'human power' with the throttle.

Frankly, the first thing I'd try is contacting the bike folks and check if they have a throttle-only controller version. This would just be a firmware change since the basic unit already could accept a throttle input via the torque sensor input (electrically anyway). They might have something on the shelf that isn't offered commercially if you talk a bit about a medical condition, etc... Anyhow - might be worth a try...

 

[ecycler]

You guys across the pond do have quite the nanny state. There is just not a lot of info out about these bike. After some deeper googling it appears that the post above is going to be your best/easiest option unless the manufacturer can help you. They hid the controller in the motor and unless you have the skills/tools/expertise to crack it open and test some things I no longer recommend you try - especially at the prices they are charging for replacement parts!!!

If talking to the manufacturer doesn't work and you really need to do this, it may be easier to just order a cheap entire electric bike kit and replace the front wheel/motor/controller and wire up the throttle.

 

[shambolic]

Okay, thanks for the advice. I did talk to Ebco themselves and they didn't think it was possible. I shall have to have a think about this. :|

 

[teklektik]

I did talk to Ebco themselves and they didn't think it was possible.

It's unclear what 'it' is.
If you mean a throttle, then quite possibly not.
If you mean hooking a throttle to the torque input - then it almost certainly will work. The difference is that the throttle will behave like an infinitely adjustable assist level adjustment rather than a throttle. This comes because you adjusting the fake rider torque and passing it through the PAS algorithm rather than controlling the motor power directly. (In fact, you will want to set any built-in PAS assist level as high as possible and just leave it there.)

The important thing here is not whether this approach will work so much as that you will trading a more sophisticated torque-sensing PAS system for a simpler RPM-based PAS system with readily adjustable assist from zero up to something like an effective 100Nm of pedal force. This is an issue of riding experience - which will definitely be different.

• FWIW - I use a CA V3 to provide PAS and have the CA configured for a torque-sensing setup virtually identical to yours. I use a two hall rpm sensor (like yours) but instead of a torque sensor, use a potentiometer feeding the torque input to set the assist level - the same as the throttle scheme suggested above. Works great (see build thread). The technique is discussed in the CA V3 Unofficial Use Guide. A technique for converting a thumb throttle into an assist-level adjustment that will hold the setting when released can be found in the CA V3 Beta thread here

Anyhow - depending on your tinkering skills this might be worth trying as an afternoon project. As a wiring change between the sensor and the controller, it can always be backed out and the drive restored to its original operating mode. If this kind of stuff is not that familiar to you, then it's clearly a more challenging task and perhaps not an attractive option.