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Articsimulator - Joyrider made of wood

Discussion in 'DIY Motion Simulator Projects' started by fredspeed, Nov 6, 2009.

  1. Frakk

    Frakk Active Member

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    The connections are right. Wiper goes to signal, + and - can be reversed if you want to invert the pot's rotation.

    The only way to connect it wrong if you connect the wiper to one of the power connections on the board. In this case you make a variable resistor between + and -, where one end of the pot will be the maximum resistance and the other end a direct short @ ~0ohms. It will burn the pots, but the USB power regulator should limit the current to protect itself.
  2. fredspeed

    fredspeed New Member

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    Thanks Frakk. I am working on a pedal-set just now. I understand from the manual that you can calibrate the Mjoy axis. Does it mean I can use just a part of the travel of the potentiometers? (if not I need gearing on them)
  3. Frakk

    Frakk Active Member

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    There are multiple levels of calibration. You have to calibrate in the windows game controller settings first, which should take care of everything. Some games also allow you to calibrate the inputs in their control settings on top of the calibration.

    You should not need gearing in any case, however, using 100% of a potentiometers travel will give you best resolution. 90° pots are the best suited for pedals.
  4. fredspeed

    fredspeed New Member

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    Happy new year folks! :hi:

    I am starting this year finishing my second h-bridge, and today I am planning to test it. Things I have done since I destroyed my first:

    The motors and pots are mounted so the motors can run unlimited without breaking the pots. I have done this to avoid the motors to stall and burn fets. The pots is connected to plattform not to motor.

    I have connected amp-meter and volt meter. When I test motors on battery the ampmeter peaks quikly to 30 amps, but is stable at 5 amps whith no load. When starting both motors at the same time it peaks up to near 60 amps very shortly, and its stable at 10 amps. When I but some load at the platform the ampm does not rise more than a few amps. seems to me that starting motors draw most current even without load. Guess this is basic to most of you, but does this seem ok.

    I have made som bigger heatsinks

    A friend of mine recomended thinner cables because they could limit some of the peaks. Is that right? I am also twisting the cables as recomended somwhere in this forum

    And ofcourse now I am using logic level mosfets...and small fuses (7,5 amps)

    I will also follow the starting sequense R-eng posted at page 9.

    Anything else I should consider??? I hope not to make any fireworks today because there was enough fireworks last night!!! :cheers:

    Fred
  5. Frakk

    Frakk Active Member

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    Happy New Year to you too!

    Yup, thats what DC motors do. They draw the most current at 0 speed since no back EMF is generated. You can measure the series winding resistance to calculate the stall current. Ex: you measure 5ohms between motor connectors, 12V/5 = 2.4A.

    Thinner cables will only make things worse. The only reason they would limit your current is because they have higher resistance. I don't think you want to make fuses out of your cables. :)

    The concept of twisted pair only applies to differential communication signals to cancel out the noise on each other. It will not impact your power lines.

    If you are drawing more current than your motors stall current, your bridge is probably shooting through to cause those high spikes.


    ps. Did re-program the MJoy?
  6. fredspeed

    fredspeed New Member

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    we had electrisity power shut down today in my area (no no no, not my fault!!! :uups: ) so I havent done much today. have to attend a coffe party too...

    My bridge is not connected yet, it was just a test of how the motors was, before testing h-bridge. I guess they can draw a lot of current if there i something wrong with them, but i believe they are ok

    Mjoy. not programmed yet, but I will give you feedback. I have ordered a new atmega from ebay just in case (god to have an extra anyway).

    Fred
  7. fredspeed

    fredspeed New Member

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    Seem to me I am not able to build functional h-bridge. Status now: i have build two h-bridges. One is working at motor 1 and the other only working on motor two. Both of them seem to have a shot thru, i did not even get time to try the last one with load before fuses burned. No heat on the heatsink either, so I really dont know if the mosfets are gone, but the fuses burn even with no motor connected, so i guess the are. Frustrating to almost have made it, but I think i must deside to cancel this project, at least with Thanos h-bridge. I think I need a break, and when i get motivated for this again i will look at the progress in other solutions here as the polulu and welleman.

    Fred
  8. fredspeed

    fredspeed New Member

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    Well well,,, Cant ceep my hands from my project while i have available time. Now i am waiting for part for a relay-motor driver,and while waiting i had another look at my h-bridge. Testing it with a small dc-motor (without fuses) both sides seem to be ok. That leads to some questions:

    Why does it work with small dc, and burn fuses with my viper-motor?
    I guess there is no shoot-thru/burned mosfets if it works with dc-motor?
    can it be something wrong with my vipermotor, though its is working fine connected to battery?
    I am using 7,5 amp fuses.
    maybe there is still hope for this bridge!?!?!
    fuse.jpg
    Fred
  9. egoexpress

    egoexpress Active Member

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    Is your wiper motor GND isolated from the housing?
    Check if you can run the motor by connecting one wire to the housing (a surface without paintjob), while the other is connected to a wire.

    regards
  10. fredspeed

    fredspeed New Member

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    It is not. I will try that. I guess it is the same if it is - or + because the polarity is changing anyway? (must see if I have some fuses left :)
  11. egoexpress

    egoexpress Active Member

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    Yes, polarity is changing when used with h-bridge. I was referring to GND because of its origin... a car.

    Most automotive wiper motors have GND via the housing. In this case the Motor MUST be isolated from the housing, as the motors will create a shortcut via the their housings and overheat themselves including the MosFets!
    There is a tutorial on how to isolate wiper motors here in the forum.
    Or look out for some isolated wiper motors.
  12. fredspeed

    fredspeed New Member

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    My vipermotors have a cable that vas connected to the housing/mounting bracket. and two cables - and + I have been using those two cables. In the picture you see the gnd-cable to the right, and the cables I used is to the left with the socket on. Search engine here dont work well, but i will find that post about isolating. i believe i have read about it somewhere :yes:
    v-mot.jpg

    Fred
  13. fredspeed

    fredspeed New Member

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    And here is a couple of pics of my h-bridge, in case you wonder how my work looks like. :D h-br-b.jpg h-br.jpg
  14. egoexpress

    egoexpress Active Member

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    You have to use the black cable as well!
    Connecting both cables from the h-bridge to the socket is wrong.
    I cant tell just from the picture. But Imho the two wires on the socket are + for slow and full speed (when mounted in car). I just dont know if the motor has full spead with either one of the wires connected, or both together.
    But for sure is, that the motor must not move, if you connect one of the power supply wires to the housing.
    I couldnt find the thread either, but here is a german one with lots of pics.
    http://www.rn-wissen.de/index.php/Trico ... schermotor
  15. fredspeed

    fredspeed New Member

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    So I have learned something today also! still not tried with h-bridge, but connecting one of the wires to black and housing turns the motor. So if I connect both the wires on the socket there will be no sparcs only more speed? must take a deep breath before I try :lol:

    Fred
  16. fredspeed

    fredspeed New Member

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    Connected to h-bridge again. Motor 2 side still working ok. Motor 1 burns fuses. I noticed something that might tell something: The motor first turns, but slover than on motor two side (same motor) When I turn the potentiometer the fuse burns emidietly when the motor change direction! There was shoot thrue on my first h-bridge, an connecting hbridge to power burned fuses without connecting motor, only power. this is not the case with this one. With the small dc I do not use fuses, and it works. Is this the case if i have damaged mosfets on that side??? Maybe I could cut both h-bridges in two and merge them, because I have to bridges working on one side?! :rofl:

    Fred
  17. Frakk

    Frakk Active Member

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    egoexpress is right, the 2 connections of the socket are the (+) high/low speed, and the casing/ground is your (-).
    The case doesn't have to be isolated, you just have to make sure it doesn't touch anything conductive.

    Have you tried with larger fuses? You said the motors draw ~30A for very short times. This can easily blow fuses unless they are slow acting.

    The small DC motor is working because it is small... :D
  18. fredspeed

    fredspeed New Member

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    I guess I have to make a small simulator then :D So its a god idea to connect both cables to increase speed, and do you believe there is no shoot thrue? I vil make a close-up clip vith my dc-camera of all the traces in my h-bridge to look for shortcuts, but a have almost stirred it to death. :eek:

    Fred.
  19. fredspeed

    fredspeed New Member

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    30 min. with my project today... I do not know what is the best way to use the multimeter to test components on my h-bridge (Still waiting for relay-driver parts) but i checked resistance on the diodes today and compared them. The diode pointed out on the picture shows 2k, but the other diodes, showing 6k. On my other bridge where this side is working, the diode also shows 6k. Could this be the reason this side of the bridge do not work. I guess its a faulty diode? happy for any feedback on this and tips on checking other components too.
    diode.jpg

    Regards Fred
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  20. fredspeed

    fredspeed New Member

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    Strange... When the diode I pointed out is replaced, it still has a resistance of about 1,9k. When the diode was unsoldered, it shows 4,8k and the same diode on my other h-bridge also show 4,8k. How is this posible? also replaced the capasitor next to it, but no change!