Troubleshooting - One Phase of Motor Not Firing After Crash

[myelectricbike]

Unlike most ICs Hall sensors are normally advertised with a disclaimer not to use them in medical equipment or in space lift off vehicles or in any situation where life and death may be dependent upon them without first obtaining written approval from the legal department. Be sure to read the warning label on the datasheet.

Its the heat and mechnical stress in motors that kills them. Leads become brittle and the innards want to change their silicon into silicon dioxide so they can kool off.

In hub motors the problem comes from both expansion and contraction stress of the mounting points as well as from thermal damage.

If you need to buy any then best to buy 10.

Also, be aware (which it sounds like you are not) that the outputs of these sensors sink rather than source.

[jeremy]

I had a chance to test these sensors with a multimeter tonight.  It was apparent right away that the sensor on the green lead is the source of my problem.  The voltage, as you said, does not drop as the wheel rotates.

An order of new sensors is en route and will be here soon.  I assume it will be easy to swap out the bad sensor for a good one.  I have basic soldering skills and so on.  Plus, now I have a multimeter by my side.  But is there anything special I should be aware of before I make this repair?

As always, many thanks.

[myelectricbike]

The sensors are usually mounted on the same side as the wire entering the hub but no guarantees. When you pull the hub covers be careful not to mar them as they have to be pried loose from the wheel very carefully. Realize that they hold the axle and stator in place against the force of the rotor magnets so you will hear a pop when the cover breaks loose from the wheel. Then its a matter of gently slipping the bearing and cover assembly off the axle - may take a drop of oil.

If the sensor board is on the other side then you'll have to pull the other cover but leave the one you have pulled off.

You'll notice all leads are cable tie secured to the stator yoke spokes and the sensor board is likewise secured to the windings. Make a drawing of all these points and a detailed drawing of the circuit board, sensor leads etc. or use a digital camera to take pics or video. Start filming now because you will need a record for later.

If you are skilled with a soldering iron and solder wick or vacuum you can remove the solder from each lead on the board. You can sometimes make a wick with very finely stranded copper bundled together with insulation removed.

Once all solder has been removed cut the nylon ties that secure the circuit board, gently separate it from all the leads and put it away for later.

You can now power each sensor and test them individually. Pull any bad sensors, clean out the sensor well, insert the new sensor and super-glue it in place with bottom touching bottom of the tapered well.

Now again use your brand new ohm meter to test each sensor lead for continuity from the Molex connector right up the point where it was soldered to the board. Check the supply leads to. I move my leads around during the test to be sure there is nothing intermittent. If you find any opens or shorts repair or replace them.

At this point you can decide whether to beef up the power phase lead wiring. I took this opportunity to replace all of them with 16 AWG Teflon insulated silver and I don't regret it.

Now solder everything back together, remount and secure the board. Test all of the sensors once again from the Molex connector. If everything is okay then re-secure the wiring inside the hub, be sure the board is not too high that it makes contact with the hub cover and reinstall the covers.

You should now be good to go.

[OneEye]

While you're in there fixing things and taking pictures, be sure to post them here for all to see.

[jeremy]

I replaced the hall effect sensor with a new one tonight and the motor works better, but now I have a different problem.  While riding and applying the throttle, the motor produces a really strong vibration and very little power.  While held off the ground, the rear wheel will spin basically fine, except that it needs to be pushed forward (or backward) to jump start it.

After swapping out the sensor, I tested each sensor.  All three rise from 0.02 volts to 4.27 volts 23 times around the wheel, except the sensor connected to the white yellow lead, which rises from 0.01v.  I did not create a complete table to document the wave pattern, but what I saw seemed consistent.

What should I check next?  Should I replace the other two sensors, so all three are identical?

By the way, I took a bunch of pictures documenting how I changed the sensor.  These will be up in a how-to on Instructables.com this weekend sometime.  In the meantime, I attached a picture of the bike I'm trying to bring back to life.

[myelectricbike]

White lead? You should have yellow, blue and green with red for sensor +5 volt supply and black for ground.

Yes, replacing all sensors is a good idea since opens can be (and usually are) intermittent but it could be the leads rather than the sensors. I'd replace the remaining sensors first after quadruple checking the leads and then if that doesn't solve the problem I'd replace all the leads, taking advantage of the opportunity to replace the power phase leads with Teflon/silver to the windings.

[jeremy]

Yeah, sorry, the lead is yellow.

I will replace the remaining two leads and check the wiring for continuity, but what did you mean by "opens"?

... since opens can be (and usually are) intermittent...

[jeremy]

Now, all of the connections have been checked and the sensors have been replaced, but the vibrating, which is now more like banging, is worse.  The only conclusion I can come to is that these are the wrong hall effect sensors, unless there is something wrong with the controller.

The new sensors are similar in shape and everything, except the originals and the new ones have different markings.  The old ones say "HX41 703" on the front and the new ones say "S41 632".  I tried to trace the part number back to a manufacturer, but I haven't had any luck.  Any ideas?

[myelectricbike]

The markings sound okay - I'll get back to that later...

You now need to check the continuity of the power phase leads with the ohm meter to be sure there are no opens which means breaks, disconnections, we use to be one wire but now we could be more than two, etc. (with power phase leads disconnected). make repairs or replacement as needed and remember its a great opportunity to replace um with Teflon/silver 16 AWG.

Now, using your volt meter and an additional 3 columns on the spreadsheet you used to record the sensor outputs and starting at the same location, record the voltage on each power phase lead outputted by the controller as you again slowly turn the wheel. Look for anomalies in the data when you are finished. 

The problem you describe sounds like sensor or power leads that could also be in the wrong sequence.

[jeremy]

I did a quick test just now.  The wheel behaves the same whether the green power lead is connected to the motor or not.

Tomorrow I will repair/replace this lead and report back.

[myelectricbike]

Now about markings... It's normal in production electronics to use whatever parts are available from different manufactures and suppliers so long as the parts fall within the required specs. A 15 ma sensor and a 7.5 ma sensor may be okay in the circuit but naturally have a different code number. Different runs of the same part may have different prefixes or suffixes. Usually these numbers are for the benefit of the manufacturer rather than the end user. Many production parts do not even have code numbers! SS41, however, is the right part for this motor and I've used less expensive crossovers from other manufacturers with equally good results.

[jeremy]

I can't thank you enough myelectricbike.  There was a gap near the controller on one of the motor's power leads.  I fixed that right up and now everything works.  It's good as new!

[myelectricbike]

Glad you found it!

After discovering how fragile the multi-pin male connectors pins are I moved to a European-Style Mini Terminal Strip

(Radio Shack Catalog #: 274-680 $2.59) and I'm still looking for the best type.

I found the Anderson Power Pole connectors at a little bit lower price ($19.95) but found that a couple of extention cords with grounds cut in half can be adapted as positive and ground dongle disconnects by twisting the two leads and ground into a single wire.

[jeremy]

Hello all. 

I posted pictures and instructions to make the repairs described in this post:  http://www.instructables.com/id/EWL8QR1F3SYTODB/

[OneEye]

Thanks, jeremy.  I read through it earlier today.  The instructable looks good.

-Mike