Struggling to get this MC33035 to work, can anyone help at all?

Thread Starter

Lawrence White

Joined Jan 7, 2019
8
Afternoon everyone,

Getting rather frustated with somethign that seems straightforward to me...

I have researched and corrected any mistakes I have made, done a rebuild several times, but can never get this thing to work. draws about 10mA on a 12V test voltage and thats it. nothing seems to work...

ive been following suggested schematics and pulling from them what i can.

little difficult to diagnose what is wrong as i dont have an oscilloscope to test certain parts, but voltages on VC and VCC are fine.

None of the motor phases are getting any power to them at this time

Am i doing something wrong here?

See below for current schematic...

smoothing caps in place where needed, not shown on schematic.
 

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wayneh

Joined Sep 9, 2010
17,153
I cannot comment on the circuitry overall however I have one piece of advice - divide and conquer. Put LEDs in place of the MOSFET gates, to get visual feedback of any signals there. Likewise you can manually set the gate voltages to make sure the MOSFETs switch as intended when provided the expected signals. You may want to substitute a light bulb for the motor coils. Good feedback and less risk.

Your attention can then likely focus on the IC. An obvious question is whether it's still functioning properly.
 

Marc Sugrue

Joined Jan 19, 2018
217
Afternoon everyone,

Getting rather frustated with somethign that seems straightforward to me...

I have researched and corrected any mistakes I have made, done a rebuild several times, but can never get this thing to work. draws about 10mA on a 12V test voltage and thats it. nothing seems to work...

ive been following suggested schematics and pulling from them what i can.

little difficult to diagnose what is wrong as i dont have an oscilloscope to test certain parts, but voltages on VC and VCC are fine.

None of the motor phases are getting any power to them at this time

Am i doing something wrong here?

See below for current schematic...

smoothing caps in place where needed, not shown on schematic.

I'm not familiar with the device but the brake line looks like it needs to be pulled down for the Motor drive to run and you have pulled up. There appears to be an internal pull up so just connect it to GND.

The datasheet says
" A logic low state at this input allows the motor to run, while a high state does not allow motor operation and if operating causes rapid deceleration."
 
Last edited:

Thread Starter

Lawrence White

Joined Jan 7, 2019
8
I'm not familiar with the device but the brake line looks like it needs to be pulled down for the Motor drive to run and you have pulled up. There appears to be an internal pull up so just connect it to GND.

The datasheet says
" A logic low state at this input allows the motor to run, while a high state does not allow motor operation and if operating causes rapid deceleration."
ah, yes i saw this, i have since corrected, thank you :)
 

Thread Starter

Lawrence White

Joined Jan 7, 2019
8
I cannot comment on the circuitry overall however I have one piece of advice - divide and conquer. Put LEDs in place of the MOSFET gates, to get visual feedback of any signals there. Likewise you can manually set the gate voltages to make sure the MOSFETs switch as intended when provided the expected signals. You may want to substitute a light bulb for the motor coils. Good feedback and less risk.

Your attention can then likely focus on the IC. An obvious question is whether it's still functioning properly.
hadnt thought of that... ill have to work out a way to best do this... thanks :)

Your attention can then likely focus on the IC. An obvious question is whether it's still functioning properly.
thankfully, when working on these types of IC, i always buy a few of them, so wil be sanity checking that again also
 
The high-side P-ch mosfets should have their source connected to power, not the motor (load). See, the body diodes would always keep power to the windings and damage the N ch mosfets then, as you have it drawn.
How do your hall-effect sensors get power? I don't see power or GND going to them.
The gate-drive resistors R19, R1, R20, R2, R21, R3 are in the wrong spot, and give 1/2 VCC as drive, you may not want this. Move them to the other side of the gate series resistor. Brake switch should go to GND, not +12V.
 
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