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Articsimulator - Joyrider made of wood

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

  1. fredspeed

    fredspeed New Member

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    OK. I did as you said Frakk, and I have read a little about shoot thru. Does Thanos H-bridge have this Shoot thru -protection Can I risk that the same happends again if I replace Mosfets on M2? I have isolated Power from M1 and M2 with separate fuses, and its only M2 that burns off.

    Fred
  2. fredspeed

    fredspeed New Member

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    Discovered something about my Mosfets too: I ordered first from digikey, and later replace-mosfets from futurelec. When I soldered I used all IRF4905 from digikey and IRFZ44 from digikey on motor 1 and from futurlec on motor 2.

    Deskriptions on mosfets Motor1:
    FZ44VZ
    844p
    IM LD

    M2 mosfet:
    IRFZ 44n
    815p
    ET HA

    Does this matter?
  3. R-eng

    R-eng Member

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    @ Fredspeed

    For the older version of X-sim (1.6.9) I found it critical to start things in a very defined procedure, otherwise 128 would show across the LCD on the AMC. This is a non-communicative state, and it can cause all sorts of problems. Here is the starting sequence I have used with total success.

    It appears you jammed the motor2 in one direction and it damaged the H-Bridge on that drive. I did this a few times also, and this startup sequence solved at least this problem of non-complete communication between X-sim and AMC.

    NEVER start the sim motors if all you see is 128/128 on the LCD. It should read 127/127 when in the neutral position of the motors.

    I even use this sequence for safety with X-sim2, and never a problem.

    Don't use fuses larger than 5-7A until you know everything runs well when the sim in not loaded. Better to burn cheap fuses than damage to H-Bridge!

    R-eng

    Attached Files:

  4. Frakk

    Frakk Active Member

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    Fred, first of all, you need to use logic level MOSFETs for the low side N-channel ones. I thought we already discussed this and I was under the impression you had these and not the regular ones.

    You need: IRLZ 44n, and not IRFZ 44n. You can also use any other LOGIC LEVEL N-ch MOSFET that meets the current requirements.

    No, there is no protection in the h-bridge for shoot-through, and neither dead-time (bottom MOSFET waits until top one turns off completely).

    About your question on the Pololu drivers: You can connect them directly to the AMC, in place of the dMSHB. They have dual or single drivers, personally recommend 2x single drivers in case something goes wrong.
  5. fredspeed

    fredspeed New Member

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    OK. I ordered my Mosfets more than one year ago, and I believe I missed the discussion about Logic Level mosfets. Its hard to get the right parts where I live because I am depending on internett-stores that distribute international.

    Now I must deside if I should order new mosfets, or try Pololu drivers. Do you know anyone that use them together with the amc and Vipermotors? Do amc need new firmware to run this drivers? I guess if you use two single driver you must connect one to motor 1-2 output on amc, and the other on output for motor 3-4? (if one dont ask he never learn!)
    :uups:

    Fred
  6. fredspeed

    fredspeed New Member

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    I am not shure about what to do with my H-bridge now. It is working strange. When I first tested with one motor it seemed to be ok, but now neither of them are vorking. The motors run a little bit, but very slowly. I have ordered logic channel mosfets, but I am not shure it is the mosfets that is gone. i have replaced the mosfets on the side that is not working, but it did not help (not logic channel, I had some IRFZ 44n) I hope some of you can ansver some questions here:

    Is it common that other parts of the h-bridge is damaged when the mosfet blow up?
    How can I test mosfets one by one without connecting them to the bridge?

    For me it is the same costs building a new h-bridge as it is to order some Pololu motor drivers like this: http://www.pololu.com/catalog/product/706 , but I dont know if anybody have tested them vith amc and how to connect them. If somebody can support me with knowledge on how to do it I will be happy to try it out, so others can benefit from it. :highfive:

    Fred
  7. Frakk

    Frakk Active Member

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    Troubleshooting electronics is hard enough for trained technicians with proper test equipment. I can keep guessing here from a distance, you can keep trying, in the end we might just fry more MOSFETs without really fixing anything.

    To answer your questions: MOSFET's can definitely damage other components, the components that drive their gate. They usually short between Drain-Source when they blow, but they also short the Gate pin to source, effectively shorting the gate driver circuit to ground, blowing the rest.

    To test the MOSFETs, you need a multimeter with a diode check functionality. Do you have that?


    There are a lot of people that tested those Pololu bridges, but not for our applications. They have the PWM connection for speed and INa/INb for direction and braking. The AMC has just this, PWM and 2 direction outputs, so all you have to do is connect wires correctly.

    I will help you hooking it up, but it is simple enough. Make sure you read about their power and heat dissipation! You will need to cool them.
  8. fredspeed

    fredspeed New Member

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    I have read that they needs cooling, and they say it must be connected on the back side of the board, will try to find a picture of them from the back of the board to see how it can be done. i guess one can also mount a fan. Good to know you can help me Adam if I deside to use them. It maybe useful to make a topic for the testing of this bridges if I do that. Right now my h-bridge is totally dead so my alterantive to Pololu is to solder a new h-bridge. I have an unused pcb for it, but need the parts, and I will post some ??? about parts on H-bridge topic. I am also considering making the Mjoy-usb controller, just to give myself even more headache :D

    Fred.
  9. Frakk

    Frakk Active Member

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    You can just stick an appropriate size motherboard or cpu cooler on the back with a fan, no big deal.

    If you want to resolder everything, I would reuse the current board and change only the components. You could sell the other board to make some money back for the parts. How much is it going to cost to re-build the h-bridge roughly?

    I have a spare Mjoy board I designed for sale in the Marketplace section with pictures if you are interested. I also have most of the parts laying around too.
  10. fredspeed

    fredspeed New Member

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    When I order from futurelec it will be around 30 dollars incl. shipping. My experiense from digikey, is that they have all you need, but the price incl shipping gets high. When i order parts for my h-bridge i can also order parts for mjoy at the same time. I intend to just use a proto-board for it. You can pm me the price you want for your mjoy board. I give h-bridge one chanse, but will consider pololu later

    Fred
  11. fredspeed

    fredspeed New Member

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    Waiting for parts for a new h-bridge and Mjoy, I desided to make a h-bridge inspired by the ideas from diy-h-shifter-by-willynovi-working-t2323.html I have used stuff that was laying around. so the design and finnish could be better, but it feels pretty realistic. I have mounted microsvitches and hope to build a Mjoy usb controller to make it work in my sim.

    http://www.youtube.com/watch?v=mxbpnQsyICA IMG_0008.JPG IMG_0022.JPG

    Fred 8)
  12. whaleman

    whaleman Member

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    Hi Fred! I had also some trouble with DShmb so I decided to order Pololu VNH2SP30 boards. Once I get them tested and running, I'm happy to share my experiences with them.

    @Frakk: Is it possible to cover the whole backside of the board with a single cooler? So that it won't result in short circuits between components? I haven't seen the backside yet.
  13. fredspeed

    fredspeed New Member

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    Hello Whaleman. Looking forward to se how it goes with your Pololu VNH2SP30 boards. I suggest you make a topic for it for discussions, info and help using them. I have just got new components for h-bridge, and will give it another try, maybe this weekend. :thbup:

    Fred
  14. Frakk

    Frakk Active Member

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    The whole back side should be covered with soldermask (the green layer), and that will insulate the electrical connections. Solder joints will interfere with the heatsink, so it has to be smaller than the entire board to allow room for these connections.
  15. whaleman

    whaleman Member

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    New topic for Pololu is a great idea, I'll do that. And good luck with new components!

    About your mechanics, looking very good so far! I really liked your tornadoblu style design. It's not a bad idea to make something a bit simpler and then make evo II sim later if required. IMO adding a yaw axis to tornadoblu style design would be very tempting as there wouldn't be problems with monitor's position like in fixed monitor setups.

    I can see you have put effort in that H-shifter of yours. Little bit of fine tuning in the exterior side and it will also look great. :thbup: Much more complicated mechanics compared to mine H-shifter, but I bet yours feels more realistic. I'll post some pics of mine in my topic some day.

    And thanks Frakk for quick response!
  16. fredspeed

    fredspeed New Member

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    The h-shifter is not very complicated to make. i used a simple metal-saw and a grinder, some iron angels, one hinge and stuff laying around. Its compact, so i will try to use a gear-rod-cover (if that is the name) to cover the mechanics. If a standard dont fit, i make one myself :yes:

    Fred
  17. fredspeed

    fredspeed New Member

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    I have startet to solder a new h-bridge. I did a last test on the old one and this is what happend: Changed all the mosfet, bc546, 74hc08 and the capasistors. Tested on a small 12v motor, on motor1 side. All seemed ok. Tested on motor 2 side and then: Motor starts but the speed varies without turning potentiometer. The strange thing is that the green led on the motor1-side lights up When I started motor 2. After a short period the mosfet on motor2 is very hot and the fuse burned. Hope to finish my second bridge later tonight, but comments on this are welcome! :?

    Fred
  18. Frakk

    Frakk Active Member

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    That sounds like a short between the 2 motor terminals.
  19. fredspeed

    fredspeed New Member

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    I was thinking in that direction. The space between the traces is narrow, espesially when you put a large amount of solder on them as thanos described. i have not found any shortcuts yet, but will keep loking. This maybe the actual problem with my board!

    Fred
  20. fredspeed

    fredspeed New Member

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    I have learned that its never a bad idea asking questions. I bought a finished Mjoy from our friend Frakk here, and it looks very pro! Now I want to be 100% shure to not doing anything wrong with it. so here is the questions: Is there a risk connecting pots wrong besides burning the pot. i think i know how to connect it but must be shure.
    IMG_0173.jpg
    OK?

    Fred