sparkfun moto monster only one direction

Hi all,

I ask you some support in my DIY motion simulator, 12V DC wiper motors, arduino + sparkfun moto monster project.

I based my project on RacingMat project. Big thanks to him for this detailed project. It is very helpfull.

So I used an arduino, linked to an sparkfun moto monster as depicted in the project. It work well but the motor choosen do not go in reverse direction. I am blocked at this step since some months. I need help to analyse the problem.

A picture of the project is in attach of this post. It seems not clean. It is due to my numberous attempt to solve the problem


Summary:
- Arduino with racingMat suggested code,
- Sparkfun wired with cable (not stacked on arduino)
- alimentation through an ATX molex connector (as a first step, I use this supply for developping the project),
- car wiper motor (audi A6, for reference)

My observations:
- without any load, the behavior of the moto monster is ok : the led showing the direction of the output varies well with the value of the potentiometer. the measured voltage goes from positive values to negative.
- with the load (the wiper motor), the motor run in forward mode. But it do not move in revese mode. The voltage measured in this operating condition is only ~-0.5 V. The led showing the direction are both ligthing, despite the full rotation of the potentiometer. (note : I tested it at full pwm : pwm = 255)

At first, I though my connection to the moto monster was bad (bad brazing?). I order a second one to do it better (this time the connection is good!), with the same result.
I changed the supply to avoid power limitation : server supply hp DPS-600. With the same result.

Investigation :
- with a lower load (a inkjet dc motor), the motor run in forward and reverse direction. I remark that to control the motor, I had to provide high level of PWM (first attempt at 100 was not enough, 200 worked well)

I found some refernce on the web, without help for me :
- http://forum.arduino.cc/index.php?topic=323689.0
-http://arduino.stackexchange.com/questions/6752/arduino-motor-shield-will-only-work-in-one-direction
- http://www.x-sim.de/forum/viewtopic.php?f=37&t=943&start=70

Thanks for your help!

In pictures!

Hello,
the last link you postet, it was me with the problem. It is some years a ago and i switched to a pololu one. But for my current build I'm using MM again. I still have this MM laying around and can say it was just a defect MMin my case. All the ones i ordered last 2 years where ok.

Yup !

Thanks both of you for your suggestion. You are right!

My motors were not internaly isolated (but still ground isolated as fix it on a wood board!). By the way, I never read about ground isolation in the post a came across. Ground isolation is now done. For the record, I attach 2 pictures of the links inside my motors. I removed the screw (linking to the chassis) and put some isolating tape below.

I tested my MM, as suggested by
http://www.xsimulator.net/community...monster-is-this-a-valid-test.6887/#post-81238
commanded in the Sim with the pot, With and without load (=my wiper motor, or a inkjet printer motor).

I get :
lane1 : +12V/-7.5V
lane2: +12V/-8.5V

and with wiper motor load:
lane1: +12V/-0.5V

I guess the MM is faulty, despite it was ordered from a recommended ebay shop TxHang Electronic (in China). I should receive another order soon. I will test with a new MM. And hope it will be a good one!

See you soon!

Hello loco_339,
the 0.5V point to the forward voltage of a diode. Is there a diode in or at the wiper motor? I have motors with 2 different speeds each and there was a diode between the connection points. A wiper motor in a car runs only in one direction. So if you pole reversal a diode can shortcut the power.

Hello Bernd,

These motor have also 2 differents speeds. I not sure about the wiring inside the motors. All what I saw was the visible components : helicoidal wire forming an inductance, brushed motor contacter, and for one of both : a rectangular component (as on picture). Don't know what is it.
It do not think there is a diode. Does this observation can discard this hypothesis : When I connect the power directly to the motor (not passing throught moto monster) It work in bot direction for +12V and -12V.

Hello loco,
could you first make two tests before we go any further:
1. Connect the motors direct to power and measure the current (Amperes) in both directions. Is the speed identical ?
2. Connect a 12V Halogen lamp to the Motor Monster and look if it is lightning at both directions.

Hi Bernd,

(I am back after the feest of the new year ,) )
Thanks for your suggestion.

1. Connecting motor direct to power :
+12V, 8A decreasing to 4.7A stable, lower speed
-12V, -7.84A stable, faster speed

2. Connecting a light (12V 5W) to MM output :
The light intensity is higher in one direction
+9.31V, +0.27A (2.5 watts output)
-12.30V, -0.33A (4.06 watts output)

So, is it an double anomaly ? default of MM and non "symetric behavior" of the motor ?
Does the supplycan be in trouble ? (I recycled a noname ATX alimentation and use it as laboratory supply)

Would it be a bad idee to use the MM as half-bridge, as suggested in
Tutorial Monster Moto Shield acts as a single motor driver = more power! ?

Hello loco,

1. I think you did not isolate your motors correctly. A wiper motor with 2 speeds has two connection wires, the third connection is ground (chassis). If you only isolate ground internally, the third connection is missing and you are using 2 carbon brushes which are in a 90 degree angle. That seems to be the reason for the different amperes in both directions.
I've made two drawings to show the correct wiring:


You can only use the 2 carbon brushes which are in opposite direction (180 degree), the 3rd carbon brush (90 degree) can't be used anymore.

Here is a very helpful thread that shows pictures of ground isolation:
http://www.xsimulator.net/community/threads/isolating-a-wiper-motor-ground.3358/

2. It seems that i have a similar problem with one of my 3 MM's. With a small motor it runs correctly, but not with a big one.
If i have the time i will write a simple Arduino program to test both channels of the MM separately.

Sounds like a unserviceable chip on the MM to me. I have certainly seen and repaired plenty of them. I just used the SCM3 Arduino software to test them, wired to drive each chip separately.

Good idea, safes plenty of work.

Hi all,

Thanks for your heplfull return.

@Bernd Manger, thanks for your scheme and link. My motors looks like the one used for the example. My motors are now ground isolated correctly with fast speed selected and working in both directions (almost) at same speed.

@SeatTime, thanks for the reference of SMC3 software and method. How practicly did you repair some of th MM ? The SMC3 allow to test them but not to repair. I hesitate between investigating the default on the current MM and test a new one.

See you (as soon as possible...!)

MMs were repaired by physically replacing the driver chip. Not impossible, but certainly very difficult for someone without experience in the repair process.

mmm bugger, I'll keep using jrks.

at <10.dollars each and with ebay/paypal guaranty, its hard to beat monsters. As far as repairing them, I throw them out. I have not paid for 1 bad monster. I had jrk's and sold them they didn't have enough power for me, and were a pain to set up compared to the smc3. JRK's are a good solution if you dont want to solder and wire, and don't need a lot of power. JRK's seem to be a great solution for some. Waiting for mm's can suck though.

http://www.ebay.com/itm/Dual-VNH2SP...place-L298N-/191674295987?hash=item2ca0ada6b3

this is the seller i use.

My 2 cents worth is in my build thread http://www.xsimulator.net/community...ng-12v-dc-motors-mms-and-arduinos.6948/page-8

A lot of faulty MM's out there. Unless you buy direct from sparkfun you run the risk of faulty ones. I can take a photo of all my faulty ones if you would like

Yes @SilentChill i remember. A nightmare scenario for sure. How are the monsters working now?

I have had 2 die on me which were slightly faulty which I had not changed (because im lazy) they were overheating and finally blew up on me in a ball of flames literally on fire, my bum nearly set on fire too

Other than those two they have been working fine.