This time I'm taking no chances...

[chris414]

Okay so I posted the problems I'd been having with my motor controller in a thread a few months ago (https://www.electro-tech-online.com/threads/mysterious-current-flow.103091/) but was still unable to get the controller to work reliably. I put the project on hold because I didn't have the time to fiddle with it, and am now returning to get my revenge

I've decided to scrap the old controllers and start again, so basically what I'm asking is whether my new proposed motor controller has anything wrong with it. I'm studying mechatronics engineering but we have not done any theory related to motor controllers yet, so please correct me if I'm doing anything wrong! (In particular, is the cap on pin 5 of the mosfet driver (1uF) too big?)

Some background info:

• I'm making a Segway, but am having problems with the motor controller (these can be viewed in the thread I posted at the top^)
• I am using two wheelchair motors, controlled by two seperate motor controllers
• Because it's a Segway, the motors will be changing direction often
• The motors draw about 10 to 15amps stalled
• I have added 0.7 ohms resistance in series with the H-bridge so that if there is a short circuit, the max current that can flow is about 50A - which is below the current rating of the mosfets so they won't blow before the current limiting kicks in / fuse breaks

The datasheets:

• Mosfets STP55NF06 http://www.st.com/stonline/books/pdf/docs/7544.pdf
• Mosfet driver IR2113 http://www.irf.com/product-info/datasheets/data/ir2110.pdf

I have attached the schematic for the motor controller - the one image is just of the schematic, the other is divided into different sections, eg. current limiting, mosfet driver, etc.

Thanks for the help/comments! It is much appreciated

 

[chris414]

anyone with some insight?

 

[Hero999]

I'm not sure what you're asking?

The schematic does look odd.

If you're using a micro then why do you need all of those logic gates?

You do know that you can use diodes to make an AND gate?

To save ICs I'd probably replace the ANDs with diodes and resistors, the NAND can be made from two diodes, a resistor and a NOT gate, then the only IC you'll need is a hex inverter.
**broken link removed**

If you must use AND gates then go for a triple three input AND such as the CD4073 and make the NAND from a NOT gate and a three input AND with one of the inputs permanently connected high.

Still, I think non-inverting logic gates are not needed often because they can easily be substituted with diodes and resistors, most of the time.

 

[chris414]

Thanks for the tip. The microcontroller i'm using only has two PWM outputs and I need to control two motors at different speeds, so the logic is there so that the PWM signal is fed to the correct side of the H-bridge.