Dynomotion

Group: DynoMotion Message: 14008 From: yxu195@usc.edu Date: 11/8/2016
Subject: Voltage Amplifier code in SnapAmp

Does SnapAmp has some code used to amplify the input voltage? I use a 12V power supply connected to SnapAmp to run a DC servo motor. The rated voltage of my motor is 12V. However the output of SanpAmp is 10V, so the motor doesn't rotate. Does anyone know how to amplify the output voltage through programming? Thanks a lot!
Group: DynoMotion Message: 14012 From: Tom Kerekes Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp

Hi,

There isn't any way for SnapAmp to amplify the supply voltage.  SnapAmp uses a full-bridge output to basically apply the full Power Supply to the Motor output for different duty cycles.  At a maximum of 80~90% depending on mode.  To apply 12V to the motor a Supply Voltage greater than 12V would be required.

With 10V on a 12V motor I would expect it to rotate at ~80% of rated speed unless there is a very heavy load.  Are you saying the motor doesn't move at all.

Regards

TK



On 11/8/2016 12:31 AM, yxu195@... [DynoMotion] wrote:
 

Does SnapAmp has some code used to amplify the input voltage? I use a 12V power supply connected to SnapAmp to run a DC servo motor. The rated voltage of my motor is 12V. However the output of SanpAmp is 10V, so the motor doesn't rotate. Does anyone know how to amplify the output voltage through programming? Thanks a lot!
Group: DynoMotion Message: 14013 From: yxu195@usc.edu Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp
Thank you very much! Yes, the motor doesn't rotate totally without any load. And I'm sure the motor is OK because when I connect to the 12V supply, it works well.

What about Programmable power supply voltage clamping? could this function amplify the voltage? Or the voltage clamping level must be smaller than the power supply?

Thanks!
Group: DynoMotion Message: 14014 From: Tom Kerekes Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp

It doesn't make sense that the motor will not rotate at all under no load with 12V.  Maybe it is wired or configured incorrectly?  How is it wired?  What is your configuration?  How are you measuring the voltage?  The Motor terminals are switching at 30KHz so you can't reliably use a voltmeter without knowing how it will respond to that.  A simple trick is to to apply a RC filter (ie 1K + 1uF = 1ms).

The voltage clamping only limits voltage spikes normally generated by regenerative braking.  It will not raise the voltage.  Never set it to a voltage equal to or lower than the connected supply voltage or SnapAmp and the Supply may be damaged.

Regards
TK

On 11/8/2016 11:14 AM, yxu195@... [DynoMotion] wrote:
 

Thank you very much! Yes, the motor doesn't rotate totally without any load. And I'm sure the motor is OK because when I connect to the 12V supply, it works well.


What about Programmable power supply voltage clamping? could this function amplify the voltage? Or the voltage clamping level must be smaller than the power supply?

Thanks!
Group: DynoMotion Message: 14015 From: yxu195@usc.edu Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp
I use a voltmeter to test the voltage. I just follow the instruction on this page exactly. And when I replace the DC motor with another 12V DC motor, it works well. So I think there are no errors in wiring and configuring.
Brush Servo with SnapAmp

 

Do you mean the output voltage of the SnapAmp will be 80%-90% of the input voltage? In that case, I could use a 15V supply to get a 12V output.
Group: DynoMotion Message: 14016 From: yxu195@usc.edu Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp
Besides, after I set WriteSnapAmp(SNAP0+SNAP_PEAK_CUR_LIMIT0,9) & WriteSnapAmp(SNAP0+SNAP_PEAK_CUR_LIMIT1,9) on the KMotion Board, does pwmc8=100 means 2 Amps or 100/1000*2 Amps?

Thanks very much!
Group: DynoMotion Message: 14017 From: Tom Kerekes Date: 11/8/2016
Subject: Re: Voltage Amplifier code in SnapAmp

A Voltmeter won't give a reliable measurement.

I don't understand your statement: "when I replace the DC motor with another 12V DC motor, it works well"

That would indicate a bad motor.

Yes a 15V supply should allow 12V at the motor.

pwmc8=100 means 100 / 1024 x 35Amps = 3.4Amps

Regards

TK


On 11/8/2016 11:48 AM, yxu195@... [DynoMotion] wrote:
 

I use a voltmeter to test the voltage. I just follow the instruction on this page exactly. And when I replace the DC motor with another 12V DC motor, it works well. So I think there are no errors in wiring and configuring.

Brush Servo with SnapAmp

 

Do you mean the output voltage of the SnapAmp will be 80%-90% of the input voltage? In that case, I could use a 15V supply to get a 12V output.