double stacked fet trouble???

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    • June 21, 2004 at 8:23 pm #10591
      HACHI-RYOKU
      Participant
      • Posts: 286

      I did my first double stacked fets today. It doesn’t work. the non fetted steering still works, so I know it’s not the car. Can anybody give me some pointers? I can’t look up the old pics of ph2t’s and other peoples cars. The pictures all come out as X’s.

      I put all the fets on the top of the pcb and flipped the two caddy-cornered fets. I used one piece of enameled wire for each of 2 the “draht” connections or whatever thier called.

      Did I miss something?

      I am using some new fets. They are irlml2502ct-nd. Does this matter? They look like the same old n-ch fets????

    • June 21, 2004 at 10:01 pm #32287
      matic
      Participant
      • Posts: 62

      Did the single-fetted version worked?
      Did you flip the second stage fets as well? You should.
      Did you solder the wire-connected trminals of flipped fets to the PCB? You shouldn`t.
      Otherwise look for bad connection

      Edited by – matic on 21 June 2004 18:18:02

    • June 22, 2004 at 9:37 pm #32227
      HACHI-RYOKU
      Participant
      • Posts: 286

      Well, I just did the stage 2 fets. I didn’t test the first set of fets to see if they would work. I’ve done a milion stage 1 fet jobs with little difficulty. I flipped all the ones that needed to be flipped (4 total). I fiddled with the connections all night.

      I ordered some pnp fets. When they get here, I’ll strip the fets off and retry with them. They are a little easier to deal with, because they drop right into place. Maybe I can triple stack those. I’m putting them in the car with a 3.7 volt li-poly batt, so I should have plenty of juice for them.

    • June 23, 2004 at 12:30 am #32218
      micro_Amps
      Participant
      • Posts: 1290

      Sounds like it might be a soldering problem, hard to say really without hands on. Try and work through it and see which is not working, fwd or rev. If its both have a look at the power supply and see if the H bridge is actually getting voltage correctly.
      🙂 uA

    • June 23, 2004 at 12:37 am #32205
      ph2t
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      • Posts: 2088
      Quote:
      ………….. Maybe I can triple stack those. I’m putting them in the car with a 3.7 volt li-poly batt, so I should have plenty of juice for them.

      you’re an absolute nutter hachi!

      🙂

      ph2t.

    • June 23, 2004 at 5:33 pm #32200
      HACHI-RYOKU
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      • Posts: 286

      Hehehe. Thanx for all the input.

    • June 23, 2004 at 11:18 pm #32157
      micro_Amps
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      • Posts: 1290

      Triple stack and a LiPo should work very well, overkill, but hey the more the better right !
      🙂 uA

    • June 26, 2004 at 2:53 am #32128
      HACHI-RYOKU
      Participant
      • Posts: 286

      Well, the li-poly will heat up the fets and it stops working when they get real hot. This is bad of-course. I also noticed that the double stacked fets get very warm on the quad-cell that you (MA) helped me out with. I’m thinkin that triple stacked may give more flow for the current and reduce the temp a little. From what I understand though, transistors normally get warm during operation. But I still think the fets are getting too warm and need more flow for the current.

    • June 26, 2004 at 3:38 am #32127
      micro_Amps
      Participant
      • Posts: 1290

      You are probably right, might be a better option to use a higher resistance motor to lessen the motor current a little.
      :)uA

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