I-Bridge, need second opinion

Discussion in 'The Projects Forum' started by thingmaker3, Jan 15, 2007.

  1. thingmaker3

    Thread Starter Retired Moderator

    May 16, 2005
    5,072
    6
    This is for an electromagnetic "toy." ;)
    I-bridge 1.jpg
    I want to energise coils L1 and L2 when CTRL-1 is Hi and CTRL-2 is Lo.
    I want to energise coils L2 and L3 When CTRL-1 is Lo and CTRL-2 is Hi.
    I want all coils de-energised when both CTRL-1 and CTRL-2 are Lo.

    Will this work as drawn? (I know I need to throw in some snubber diodes, base resistors, and similar protections.)
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It looks like the FET's turn on as desired. One note, though - most FET's have a 20 volt limit G to S. Your 22 volt supply might cause problems.
     
  3. wireaddict

    Senior Member

    Nov 1, 2006
    133
    0
    Howdy. It looks OK to me, too, but getting the voltage dividers right for the emitters for Q1,3 & gates for Q5,9 might be tricky. Ditto for Q2,4's emitters & Q6,10's gates.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    That is a good point beenthere. Overdriving the gate is a potential problem with Q7 and Q8.

    A quick way to address this potential problem would be to open the connection between Q9's drain and the junction of R1 and Q7 and insert a resistor of sufficient value to reduce the gate drive signal to a level more in keeping with the manufacturer's recommended maximum. This same treatment could be applied to subcircuit Q10, R2, and Q8.

    This solution is acceptable only if the increase in turn-on time for Q7 and Q8 introduced by this circuit chnage did not adversely impact the circuits operation.

    hgmjr
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It's a driver for a toy - it will understand an extra 40 ns wait.
     
  6. thingmaker3

    Thread Starter Retired Moderator

    May 16, 2005
    5,072
    6
    40ns? I doubt 40ms would make much difference for this application. :) I'll impliment HGMJr's suggestion. Thank you to all who have given advice thus far! I'll post an updated schematic in a few days.
     
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