Power amplifier - please help me

[nza0104]

Hello

I would like to control 2 motors, one is 6V and 740mA and another one is 5V 200mA. But my I/O board (digital to analog converter) can only give up to 10V and 5mA and the motor manufacturers do not provide any motor drives. May I know how can I drive this motors using SCB 68? Do I need a power amplifier? Can you recommend a specific power amplifier or any other alternatives? Soon I will also need to control the motors using PID or any other control algorithms.

I've tried to construct the power amplifier as in the Fig. 2 in the attachment: Vin is a 12V voltage supply and RL is a 1k ohm resistor, but it does not work. Instead of amplifying the power, the voltage and current across RL is almost zero. Or does it work with only AC input?

What should I do?

Thank you very much for your help.

 

[blueroomelectronics]

Normally you would use an H-Bridge to control a DC motor. Speed is controlled using PWM.

 

[nza0104]

Is there any other way of controlling dc motor without using pwm?

Thanks

 

[MikeMl]

Is there any other way of controlling dc motor without using pwm?...

What do you mean by controlling?

(hint: Speed, Torque, Direction, Acceleration profile)?

 

[mbarazeen]

you can use the voltage range you have to drive a PWM controller to control your motor, if what you need is a simple ON/OFF control then you can use a transistor switch. if you need a feed back control then its much complicated and you need some reference input too.

 

[nza0104]

I would like to control the angle turned by the motor and would like to implement a feedback control algorithm such as PID.
Actually, I'm planning to program the control law in Matlab/ Xpc Target, but the current supplied by my digital to analog board is 5mA and 10V voltage but my motor needs at least 740mA and 6V voltage to function. I think I need to amplify the current so that it can drive the motor.
What is the best way of doing this besides PWM?

Thanks

 

[MikeMl]

You need a linear power amplifier. Look at **broken link removed**

 

[nza0104]

thank you so much

 

[nza0104]

Sorry,

Do u mean I need to construct the "Servo Motor Control" circuit on page 8 in the datasheet? Or the "Non-Inverting Amplifier" in the first page?

Can I use the same circuit for both DC and AC Vin?

Thanks

 

[crutschow]

Do u mean I need to construct the "Servo Motor Control" circuit on page 8 in the datasheet? Or the "Non-Inverting Amplifier" in the first page?

Can I use the same circuit for both DC and AC Vin?

The "Servo Motor Control" is for providing providing either polarity to the motor (for reversing) with a single power supply. If you have dual power supplies, then you can use the "Non-Inverting Amplifier" or also configure as an Inverting Amplifier if you desire.

I suggest you thoroughly read the data sheet to become familiar with the amp's characteristics and limitations. It can save you from problems/errors in using the amp. For example, the amp will need to be mounted on a heat sink to avoid overheating and shut-down of the device, with the amp dissipated power depending upon the power supply voltages and the motor current.

The circuits are DC coupled so can be used with either AC or DC signals.

 

[mbarazeen]

I would like to control the angle turned by the motor and would like to implement a feedback control algorithm such as PID.
Actually, I'm planning to program the control law in Matlab/ Xpc Target, but the current supplied by my digital to analog board is 5mA and 10V voltage but my motor needs at least 740mA and 6V voltage to function. I think I need to amplify the current so that it can drive the motor.
What is the best way of doing this besides PWM?

Thanks

since you need to control the angle, the best way is to use step motor. you will not require a feed back too, since the count of pulse on the control pulse train will reflect the angle moved depends on step size and gears if applicable.

at start you may need to define a cordinate with some feed back( limit switch or sensors) then the required position can be adjusted by adding or substracting (reverse) from the current angle.

analog feed back may need more precision position input

 

[crutschow]

The type and complexity of the control loop will, of course, depend on what you are trying to control, and the accuracy and speed with which you need to control it.

PID is the old standard type of control loop which is still widely used, but I have a soft-spot for Fuzzy Logic control. It's not well known (although the Japanese have used it in a number of products) but it's relatively easy to implement with a microprocessor and has fast response since it basically consists of a series of If -Then statements. PID was originally developed when it was easy to perform the PID mathematical functions with the analog (computer) processing circuits available in the mid 20th century. PID functions are not so easy for a digital computer to perform since it has to do the computationally intensive digital transformations to emulate the analog integral and differential functions that a PID loop requires. PID loops can be difficult to optimize, especially with the typical non-linearities of real systems. Fuzzy logic is easier to tune and compensate for these non-linearities.

But enough of my soap box...

 

[nza0104]

thank u soooooo much