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I've tried to reproduce the NAND Schmitt triggers circuit to drive my H-bridge MOSFET as per following source:

http://axotron.se/index_en.php?page=34&chapter=0

All my design files are at this GitHub link:

https://github.com/mkeyno/H-bridge2/tree/master/update

It has Enable, PWM and direction pins that are supposed to controlled by Arduino, however my PCB doesn't work yet. I used 74HC132D & CD40106B Schmitt trigger IC and used an LED to indicate each direction, but it never turns on.

Any help is really appreciated.

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Updated: I updated new schematic base on new advises , but still has its issue (logic voltage drop)

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    \$\begingroup\$ "but it never turn on any help is really appreciated" - you are going to need to be waaaayy more forthcoming with detail if you want help. What have you wired up? PCB? Breadboard? Post photos of your physical circuit. What debugging steps have you tried? Have you checked the power supply? Have you connected the power rails for the NAND gate (you don't show them in your schematic)? Have you probed different parts of the circuit to see what voltages you get? \$\endgroup\$ – Tom Carpenter Sep 18 '18 at 22:37
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    \$\begingroup\$ You have the output of your Enable inverter connected to your PWM input. What do you expect that to do? \$\endgroup\$ – brhans Sep 19 '18 at 0:14
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    \$\begingroup\$ @brhans you were right, enable and pwm should not connected, Now I cut enable and only have 2 line(PWM & Direction) and logic work fine and forward & backward line work as opposite logic , However when not used the Mosfet shield both forward or backward line shows 5 v , which my high logic level , but when I put it Mosfet shield , voltage on both forward or backward pin drop to 2 v. I update the images , kindly check my images or if you could check my schematic of mosfet driver \$\endgroup\$ – Hamid s k Sep 19 '18 at 8:41
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    \$\begingroup\$ - and I hope C1 isn't really a polarized electrolytic. Either 'forward' or 'backward' will reverse polarize it with unfortunate results... \$\endgroup\$ – brhans Sep 19 '18 at 11:17
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    \$\begingroup\$ @Hamidsk - The files on your github link are unfortunately useless for anyone who does not have Eagle software installed. You need to use Eagle to produce easily viewable files (e.g. PDF or PNG etc.) for those readers who don't use Eagle or who are viewing this site on a mobile etc. without Eagle installed. Thanks. \$\endgroup\$ – SamGibson Sep 20 '18 at 18:01
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It isn't the input impedance of the CD40106B inverters that's the problem, it's the fact that you are totally overloading the outputs. Look at everything you have attached to each one on the MOSFET board:

  • Blue LED
  • two N-channel MOSFET gates
  • bipolar driver for two P-channel MOSFETs

You have 1kΩ pulldowns on the last two items in particular (3 loads), so it's no surprise that the inverter can't drive the control signals high.

The N-channel MOSFETs in particular need to have gate drivers, too, in order to supply the transient current that they need when switching.

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  • \$\begingroup\$ but I picked up advise on comments to increased the pull down resistor (1k->3.6k) and it increased voltage level (2->2.4) so I though I should go this way to solve the problem(before burn my mosfet ), but I'm bit lost on your comment , can you be more specific or give me troubleshooting procedure \$\endgroup\$ – Hamid s k Sep 20 '18 at 16:01
  • \$\begingroup\$ Look at the output characteristics of the CD40106B. Now look at the input characteristics of all of the loads connected to it. It should be obvious that it can't supply the current required, especially during the switching transient. \$\endgroup\$ – Dave Tweed Sep 20 '18 at 16:54
  • \$\begingroup\$ thanks @DaveTweed for reply , but can you advise me how could I solve the problem?,unfortunately I'm not electrical engineering to understand very dip technical term \$\endgroup\$ – Hamid s k Sep 20 '18 at 17:23
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    \$\begingroup\$ Actually, when you're designing circuits at this level, you ARE an electrical engineer, but a rather untrained one.That will come with time, but this project seems to be a bit over your head for now. I think I would recommend that you get a preassembled motor driver board for your Arduino so that you can move ahead with whatever it is you're trying to accomplish, and then come back to these issues at a later time. Start by studying how the commercial board works. \$\endgroup\$ – Dave Tweed Sep 20 '18 at 18:22
  • \$\begingroup\$ thanks @DaveTweed for your advise but I'd rather to keep my searching to find proper solution for this project in this forum \$\endgroup\$ – Hamid s k Sep 20 '18 at 19:56

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