TongXin (a.k.a. Nano) motor project

[Jeremy]

You might be right about not wanting a linear throttle response, Nick.

I haven't looked at the Crystalyte controller waveform yet, but going on the datasheet for the brushless controller and PWM chips it looks very much as if this controller works the same way.

The high side motor drive FETs are supplied with a PWM supply, so it looks very much as if the throttle is directly controlling the effective voltage applied to the motor. I have a feeling that the response might be a bit better if the throttle response could be made more proportional to motor torque, but am really just guessing at the moment.

I went out and measured my throttle voltages this morning and was a bit surprised to find that the threshold at which the motor starts to turn (with the wheel off the ground) is a bit above the 1V that it's supposed to be. The motor didn't start up until the throttle voltage was at 1.35V, which further explains the apparent non-linearity at low throttle settings. I shall now increase the low end offset voltage a bit and see if that makes a further improvement in response.

I haven't checked the battery voltage under load yet, Nick, but will do now, as a shiny new Cycle Analyst (see here for details: The Cycle Analyst Homepage - Ebike Amp-Hour and Watt Meter) was one of the things in my package from Justin at Renaissance Bikes!

Jeremy

 

[Tiberius]

Hi Jeremy,

Was confused for a moment there until I realised Renaissance and ebikes.ca are the same. I got a cycle analyst and its pretty good. I was sitting here thinking that if I took a micro and a current shunt and a display I could find out things like..... But I asked on here first and flecc told me such a thing already existed.

The only issues I had with installation were that eZee used a different size bullet connector to the ones normally available and I had to make a bracket to hold the speedo sensor the right distance from the spoke.

Nick

 

[Jeremy]

My Crystalyte controller luckily already has the multi pin connector for the CA, so it's just a matter of plugging it in, without needing to use extra shunts etc.

I've been playing with the tiny sensorless TongXin controller this afternoon and found out a few things about it. I haven't been able to connect it to the motor yet, as that's away at the LBS being built into a new wheel, but I was able to power it up on the bench.

My intention was to try and see if I could run it up to look at the throttle response, but this was initially thwarted when I couldn't get it to work at the maximum 30V that my bench supply will go to. It looks like it won't work at 24V, as the controller low voltage cut off seems to be set to about 32V as far as I can tell (I bodged a supply up by adding a 12V battery in series with the adjustable bench supply). 32V seems a bit low for a 36V battery cut off, I would have thought that it would have been set to around 28 - 29V.

The other thing I discovered is that the controller seems to try to start by randomly powering the phase wires initially, looking for a back emf so that it can sync up. It does this for about two seconds then shuts down.

It looks like I will need to wait until I get the wheel back before I can do any more playing about with it!

Jeremy

 

[Tiberius]

Hi Jeremy,

I assume you can't get inside it, or if you can, the low voltage cutout can't be changed.

How does a sensorless controller work? Does it look for the back emf on all phases and then decide which phase to send a current pulse to? Does that mean it could not quite get to 100% duty cycle?

Nick

 

[Jeremy]

The TongXin controller is completely potted, which has the advantage of making it waterproof, but does mean I can't get inside it to play about!

It seems to work just as you describe, as far as I can tell. Whether or not this stops it getting to 100% duty cycle I'm not sure. From it's behaviour on the bench I would guess that once it has sensed the motor phase direction it should work pretty much like a Hall effect feedback sensor motor. I can't be sure, but I would assume that it uses the two un-powered phases at any instant to measure the back EMF, so it may well be able to operate up to 100% OK.

It's slightly annoying not being able to work at 24V, but I guess I shall just have to see how it performs on the road. I'm still working on an "intelligent" pedelec controller, which may well get around the excess power problem. The only real nuisance of being stuck with a 36V supply is the added battery weight.

I've spent the past hour or two dissecting a very cheap Chinese, switched mode SLA charger. I've now worked out how to make it variable voltage, rather than fixed at 48V, so am adding a 36V/48V switch to it. I'm reasonably impressed with this charger, it's very light, quite well made and is very easy to tweak. It even has a thermostatically controlled cooling fan. The make is Yiyun, they are usually available on eBay for about £18 including postage from Hong Kong and don't usually attract VAT or duty as they are below the threshold.

Jeremy

 

[Jeremy]

I think the older Nano/TongXin motors have Hall sensors, but the newer ones work very much like the electric motors used in RC models and are sensorless. My motor just has three wires coming from it and the controller is very small indeed, it will easily fit in the palm of your hand.

The Chinese translations to English on the TongXin web site are a bit vague, plus the wiring diagrams etc they give are for the older motor with sensors. The motor specs and performance curves are also for the older motor, I'm sure, as they don't tally with the specs on the motor label. The motor and controller were supplied without instructions, but it looks easy enough to connect up, just three motor wires (colour coded), three throttle wires, a pair of supply wires, plus a pair of brake inhibit wires (which are optional).

The motor is indeed a little gem, it's very light, very small and looks to be well made. The case seems to be CNC machined from solid rather than made from a casting like most motors. All told I think this motor and controller were good value for the around £100 total cost.

Only testing will tell whether or not it's really any good though!

Jeremy

 

[giguana]

Interesting, I think some nano have sensor wires, six in total going into the motor...would love to hear the total specifications of the motor. I guess you have checked out the page from tongxin. looks like a gem.
CHINA HANGZHOU ZHEDA TONGXIN ELECTRIC CO,. LTD.

apparently the motor regulates itself through some kind of pulsewitdh feedback sensor looping radial array transmission-I didn't understand one word of what the guy wrote and there was a whole page to read about it, basically some kind of good modern circuitry. Apparently there are some disadvantages regarding how smooth sensorless is and there are no doubt advantages

 

[giguana]

I've got voice recognition and I just got the posts mixed up the wrong way round-I can't wait to see the results though! am indeed wondering whether I should open up the whole crystalyte motor and apply water insulation to all the fixtures and so on

 

[HarryB]

Interesting,
apparently the motor regulates itself through some kind of pulsewitdh feedback sensor looping radial array transmission-I didn't understand one word of what the guy wrote and there was a whole page to read about it, basically some kind of good modern circuitry. Apparently there are some disadvantages regarding how smooth sensorless is and there are no doubt advantages

I thought the sensorless version just measured changes in the back EMF of the coils to locate the position of the rotor and so apply current to the two relevant coils. Or am I missing something? I have to say apart from the roller drive weakness it is a great little motor being so light. The roller drive does mean it freewheels better but works best on a small wheel. The normal version has the usual 8 wires, 5 hall and 3 power.

 

[frank9755]

Jeremy,
Tongxin does make a 24v controller - would that do what you need? It delivers more current, so same power to the motor as the 36v one.
Also I have a Tongxin wiring diagram which I could email you if you like.
Frank

 

[Jeremy]

Apparently they don't sell the version with the sensors anymore, as far as I can tell. I think the controller does work pretty much as you describe, Harry, although it may well use the relative phase of the back EMF from the two un-powered coils to sense direction

Jeremy

 

[HarryB]

Apparently they don't sell the version with the sensors anymore, as far as I can tell. I think the controller does work pretty much as you describe, Frank, although it may well use the relative phase of the back EMF from the two un-powered coils to sense direction.

Jeremy

It would be a shame if they didn't make the sensor version anymore as you could use it with a regular controller as a replacement motor. I did try to order it (as a Nano) and Tony Castle seemed to think you could get it quite easily. I did put an order in but nothing came of it, so maybe you are right and they are not making it.

 

[Jeremy]

Sorry Harry, I got confused with the earlier reply! (now corrected).

I could get a 24V controller, but the one I have is the 36V 15A version, not the 36V 10A version. For testing I'll use some of the spare SLAs I have (I have a stack of 12V 4.5Ah ones that I managed to acquire free of charge) so it's no problem to run the motor on 36V instead of 24V.

If it looks as if it might be OK at 24V for what I want, then I can always get a 24V controller as you suggest, they are pretty cheap I believe.

I found that the Nano motor people were very slow to respond when I enquired a couple of months ago. My guess is that they are running the ebike business part time or something, as they seem to have a lot of other business interests on the go at the same time. They would have been handy for me, as their place is in Marlborough, just a half hour drive away. Renaissance in Vancouver managed to reply to my enquiry, take an order, and deliver it to me more than a week before the Nano people had even got around to replying! When they did reply it was to say that any order would take a month to fulfil............................

The other big difference is price, I bought the motor and controller for about £100, the Nano motor and controller (which is apparently the same item) is around £300. I have no doubt that I could buy the motor and controller directly from TongXin for less than I paid for it, but buying from Renaissance is quick and easy, plus I wanted a Cycle Analyst anyway, so it made sense to buy from them.

Quite why we are expected to pay a 300% markup here in the UK is a bit beyond me.

Jeremy

 

[HarryB]

I agree about the price but it is impossible to deal with Tongxin direct so you have to use a retailer. I gave up on the nano-motor even though I sent a cheque as deposit, I waited for 2 months but got the impression they were pretty busy (or disorganised). In the end I got one from a helpful guy on ebay. £64 + £18 for the controller - both 8 wire though, not sensorless. A very good price but they were the 190rpm version and so no good for you.

 

[frank9755]

I bought mine direct from Tongxin. It was a little bit slow but not a bad process. Slightly cheaper than Renaissance, but not a lot by the time the transport and money transfer charges are included.

They did not seem to have the old sensor-wire motor in stock.

I had initially approached the chap in the UK but he didn't return my email and his phone has no answering machine. I then discovered his gross margin was a little on the high side!

There's also a seller in Austria, who is sometimes on eBay. I would have gone to him if the direct route had not worked - Renaissance not having any in at the time. The Austrian chap did at least reply to emails.

Frank

 

[giguana]

Alien Electric Bicycle Bike e-bike Conversion Kit on eBay, also, Bikes, Cycling, Sporting Goods (end time 25-Dec-07 21:01:35 GMT)

this looks like and nano, perhaps an older version, but it comes with a battery and some accessories and already mounted.

 

[Jeremy]

I had a few further ideas on making a semi-intelligent pedelec controller this morning and I'd like to waft the idea here to see if there's something obvious I've missed. I intend to use a small, very simple, microcontroller to process the input from sensors and provide an analogue throttle signal to the controller.

The sensors will be two pedal crank position sensors (Hall switches) positioned to provide short trigger pulses at the very start of the pedal power stroke. The microcontroller will measure the time between these pulses to derive an average crank rotation rate.

The pedelec microcontroller will implement two control rules:

1) Below a crank rpm of about 10 to 20 rpm (exact figure to be set on test) the pedelec microcontroller will cut off the throttle voltage signal.

2) For crank speeds above the cut off rate, the pedelec microcontroller will output a ramped, variable voltage pulse to the motor controller throttle input, with a duration equal to the pedal power stroke and an amplitude inversely proportional to the crank rotation rate.

I hope that such a system will work to add power only when your legs are pushing hard, during slow pedal strokes. As the pedal cadence gets up to a reasonable rate, power assistance will taper off to zero.

To get more assistance, all that's needed is to slow the cadence a bit by changing to a taller gear.

I suppose to be legal I should also include a road speed cut off as well, but I think the motor speed limit may do that, with luck.

Jeremy

 

[HarryB]

I bought mine direct from Tongxin. It was a little bit slow but not a bad process. Slightly cheaper than Renaissance, but not a lot by the time the transport and money transfer charges are included.

They did not seem to have the old sensor-wire motor in stock.

I had initially approached the chap in the UK but he didn't return my email and his phone has no answering machine. I then discovered his gross margin was a little on the high side!

There's also a seller in Austria, who is sometimes on eBay. I would have gone to him if the direct route had not worked - Renaissance not having any in at the time. The Austrian chap did at least reply to emails.

Frank

In all my searches I never found a website to order from - but it was 9 months ago and all the sites I did find said a minimum of 100 units. So good you can get them direct but it does look like they don't do the hall sensor version. By the way what are your motors rated at - mine has a sticker with 180W.

 

[Tiberius]

Hi Jeremy,

You may have a problem. If the motor/controller is providing power at low cadence and not at high, then it is trying to drive the whole system towards a given (mid level) cadence. That's not necessarily bad, but if the loop parameters are wrong it could run away as soon as you start off towards that target speed.

You are asking it to interpret low cadence as rider putting effort in, but it could also mean rider wants to slow down.

You could do what you suggest, though, and use it as a cruise control. Slow forward pedalling raises the cruise speed setting and slight backward pedalling lowers it. More backward pedalling, or faster, puts it into regenerative braking if you can do it.

Nick

 

[frank9755]

Its rated at 180W continuous. I believe peak output is 360W

Frank