MP3 + speedometer?

[MP3test]

Hello,

[ANSWER: open the controller; unsolder the yellow wire; solder it to the pin corresponding to the yellow wire from the hall sensors connector; as a result you will have hall sensor's 0V-5V ticks at your pedelec signal wire; VERIFY THE WIRES FIRST, READ THE DISCUSSION BELOW]

I'd like to build a speedometer/odometer for my MP3. Is there any way to catch the hall sensors' data? At the picture below there is "For meter display" connector, but I can't find anywhere description of what the two wires are - "Signal Receive", "Signal Transmission".

If MP III doesn't provide the hall sensor ticks trough its connectors is there anyway to get that from the controller without damaging it?

Any help?

[MP3test]

I've got an answer from a golden motor representative, he said that the "Signal Receive", "Signal Transmission" are for some proproetary UART potocol and that the speed data is not transmitted out from the motor.

So I have two options - (a) somehow to get safely without breaking the controller the signals from the current hall sensors, or (b) to solder several new my own independently at the same radius, so the magnet there is trigering them as well.

Is there anyone that has done it that way succesfully?

How many are the original hall sensors inside the motor? Is it safe to get safely in paralles the ground signal and 5V coming out from them?

[MP3test]

P.S. Just to clarify - I will be using it with an Arduino board, which I/O ports drain 50mA.

So if I get out from the controller hall sensors' signals in parallel, will the controller handle the additional 50mA need?

[Morgen 3Eman]

Hi MP3test,

There is another way to get the signal you want, and that is to epoxy a magnet to the wheel near the controller cover, and a hall sensor on the controller cover, so you can sense each rotation.  You could then route the sensor wiring with the existing power/signal cables for a neat installation.  Really, you could place the magnet anywhere on the wheel, and the hall sensor at an appropriate radius/distance.  It may even be possible to sense the motor magnets with a hall device near the hub at the radius of the magnets. 

It has been a while since I've played with an Arduino, but I don't think the I/O ports must have 50 mA to function, but can function with up to 50 mA without damage.  A typical Input current would be in the nano/microAmp range,  while the Output can handle as much as 50 mA, depending on the impedance of the load.

TTFN,
Dennis

[MP3test]

Thank you!

Yes I have a plan to use one of those two wires that nobody knows what are they supposed to do (Signal receive/transmission).

I've read the specs of the arduino, actually it says 40mA and yes this is the max. The good news is that you say this is the mAX and it needs far too low in reality for input connections. But doesn't that mean that I can connect this directly to the 5V output of the current hall sensor? The current will go to the controller as well to my wire but since it will drain out too low of electricity, it will not hurt the controller in any way?

So the simple plan is:
- to locate let say the "Signal Receive" wire coming out from controler
- to cut it
- to connect it to one of the hall sensors 5V output

Then to use the "For Meter Display" connector's:
- Signal Receive pin
- Ground pin
and to conect to the arduino's input pins.

Will this work?

[Morgen 3Eman]

Hi MP3test

I think I better take a fresh look at Arduino literature before I say anything about exactly what to connect where.

If I understand your plan, you intend to tie into the existing MP3 hall sensor for the input signal to the Arduino, and to the controller ground for the power/signal ground.  Where are you planning to get your  +5VDC supply for the Arduino?

I'll get back to you in the next day or so.  OK?

TTFN,
Dennis

[Morgen 3Eman]

Hi MP3test

Hey, sometimes i'm old and stupid.  I don't know enough about your plans!    You have only mentioned getting signal input from the Hall sensor.  What are you planning to use as a display?  Have you thought about how to drive it? USB? parallel?   Where are you planning to physically place the Arduino and display?  How are you going to power it all?

I checked about the signal input requirement for the Arduino Uno, and when the pin is designated as an input, the probable current for that pin will be in the low nanoAmp range.  The Hall sensor will easily support this additional current requirement.  So your plan for that is reasonable.

TTFN,
Dennis

[MP3test]

Thank you very much for the arduino input check! So the plan is doable without any new hall sensors.

I hope that after I cut the MP3's top secret "Signal Receive" wire to use it for the arduino communication I will not break something hidden there that noone knows about

Regarding your questions - I will power the arduino with 12V that I get trough a DC-DC converter. There will not be any display - my plan is to modify an analog speedometer to show speed, distance and battery capacity using some stepper motors. I need the retro look. If I do this successfully I will post some pics.

By the way, why there are three hall sensors in the motor - to calculate the speed faster by getting quickly 2 time intervals or there is another reason? For my needs I think I will need just one signal from any of the three hall sensors, but now I am thinking to get data from two of them (anyway there are two spare wires to use) so I will not have to wait for full 360 degree rotation but short time between the two triggers. (I am not sure how they work and will check practically - do they trigger once in 360 degrees, or multiple times by several magnets during the 36o degree rotation)

[Bikemad]

By the way, why there are three hall sensors in the motor - to calculate the speed faster by getting quickly 2 time intervals or there is another reason? For my needs I think I will need just one signal from any of the three hall sensors, but now I am thinking to get data from two of them (anyway there are two spare wires to use) so I will not have to wait for full 360 degree rotation but short time between the two triggers. (I am not sure how they work and will check practically - do they trigger once in 360 degrees, or multiple times by several magnets during the 36o degree rotation)

The hall sensors are used to sense the position of the rotating magnets in relation to the fixed phase windings, not to measure the speed.

There are three hall sensors because it is a three phase motor, so each hall sensor controls one of the three phase wires:





Here is the Hall sensor connector on the MPIII:


The Magic Pie has 56 magnets, so there would be 28 +5V/0V pulses per revolution (360 degrees) from each of the Hall sensors.

Alan
 

[Morgen 3Eman]

Hi MP3test

Hey, I like the stepper motor speedo idea!  So are they bi-phase drive motors?  How many output pins do you need from the Arduino?   I'd love to see the package you envision.

TTFN,
Dennis

[MP3test]

@Bikemad thank you very much for the input and pictures!

@Morgen 3Eman - everything started after I ordered a "48V" speedometer from China that after I connected everything blew up as it happened to be for 12 Volts. Then after I started to repair it I came with the idea to modify it and make it digital inside. That way there will not be a mechanical drive for it to count distance and speed and will be some fun for me (this will be the first arduino project). Each stepper motor has 4 wires, so to manipulate speedometer, odometer and voltmeter I will need 12 pins.

[Morgen 3Eman]

Hi MP3test

That speedo story sounds familiar.   

Something you might consider for powering your Arduino:  Use a USB power supply instead of a dedicated DC-DC convertor.  I have found that small switching supplies work just fine on 48 VDC. And they are super cheap and easy to find as used.   By powering the Ardunio through the USB rather than 12V you reduce the heating from the linear regulator on the board, and make the whole thing more efficient.  Of course, if you already have 12V steppers, rather than 5V steppers, it may not make economic sense.  Just something for you to think about.

Make sure to include freewheel diodes across each stepper winding.....

TTFN,
Dennis

[MP3test]

I've got a nice 15A 48V-12V converter with 10mA in idle which is good. I decided to have 12V bulbs as finding the right for 48V was also difficult, so every addon now I power with 12 Volts (like horn etc).

I will have a 48-5V converter as well, just to be able to charge my phone if needed. But arduino is OK with 12V - it requires 7-12V so 5 will not be sufficient I guess?

[Morgen 3Eman]

Hi MP3test,

The Arduino I worked with could be powered by 5VDC through the USB connector, or 7-12 VDC through the power input pin.  I use a 12VDC  game? oy? laptop? power supply for turn signals, lights, etc as well.  Mine is only good for 5 amps, but it only cost me 1$ US.    I also have a 5VDC USB charger for some stuff. 

Hey, I think you have a really great idea here, with your retro/steam punk analog dials driven by digital.  What speedometer stuff are you planning on using?  I ask because when I'm happy with the drivability of my latest leaning trike I envision making a good looking one, and an analog dashboard would fit right in with my currently blurry vision of what it would look like. 

TTFN,
Dennis

[Morgen 3Eman]

Hi MP3test

Hey, I had no idea these things even existed last week, and now I find out that they are cheap and easy to get.    I found some 5V GM replacements, with 6 costing $15 US!!!!  Thanks for the education.

TTFN,
Dennis