Driving Stepper Motors

Hi Tony,

Can you provide more information on the type of stepper (unipolar or bipolar), operating voltage, and how you are thinking about connecting them?

There may be other devices that are better suited once we learn this information.

Thanks.

Hi Rick:

Thanks for your very prompt reply: The commission is for a low cost (but reliable!) agricultural control that will dispense precise nutrient/water mixes to hydroponic systems to avoid the need to have large mixing tanks that require constant monitoring: The first prototypes have been running for about a year in a polytunnel - the potatoes and strawberries have been excellent!: Now I am working on the production version:

There are three nutrient valves that control the tiny flow of nutrient concentrate into the water stream: Initially, I used solenoid valves (12volt) but they use far too much power and it is difficult to 'throttle' the valve open time: So, I have designed a small, simple valve based upon a peristaltic pump that I intend (hope) to drive with a stepper motor type 28BYJ-48: It has been used for hobby circuits but by all accounts is very reliable and durable: Voltage is 5 - 12 and I would like to use 6volts: It is unipolar configuration with a common (+) for all 4 windings: The specs vary but it looks like 100mA or so per winding: Four phase, 8-Step:

Usually, this motor would be connected using a ULN2003 driver but since I am already using a TLC5940 for the seven-segment display it occurred to me that another TLC might be used to control the three steppers making sure that only one is ever operating at a time: The whole machine which includes a lot of peripheral 'gizmos',  is controlled by a PIC:

I hope that helps and thanks again for your interest:

Regards

Tony Anslow

Hi Tony

TLC5940 is more like a dedicate LED driver which has less capability to driver a stepper motor. Both the output current and the capacity of internal free wheel diodes are reaching or beyond the limit in motor application.

The unipolar stepper you mentioned can be perfectly driven by DRV8860 (one DRV8860 for two stepper). DRV8860 is a 8-Channel low side driver with 200mA*8 outputs capacity and serial control interface. Also it is versatile to do the LED driving as well. Please refer to all the following resource to speed up your design. We have example kits and control methods to do the LED and stepper control.

http://www.ti.com/tool/drv8860evm

http://www.ti.com/tool/TIDA-00206  For LED driving

http://www.ti.com/tool/TIDA-00117  For Relay, solenoids, unipolar stepper driving

Best regards,

Hi Wilson:

Thanks for your very prompt reply and the useful info: I will start investigating straight away:

Regards and best wishes

Tony Anslow

Hi Tony, if you're open to changing motors to a bipolar stepper, you gain more options.  The DRV8833 and DRV8834 have integrated current regulation (which you can set to 100mA), and the DRV8834 has built-in microstepping for smoother rotation.

Best regards,
RE

Hi Tony,

I hope we are not throwing too many options at you. The DRV8860 minimum operating voltage is 8V, so it may not fit your needs.

The DRV8833 and DRV8834 are good fits from a voltage range, but may be not other targets. Three devices are required to drive the motors. The unipolar motors you specified can be configured as bipolar, but you may see reduced torque.

If you are willing to use 5V for the motor, the rated voltage on the motor, the DRV777 may be your best fit. You will not need current regulation. The DRV777 is similar to the DRV8860 but operate at lower minimum voltage and has a different interface. Two DRV777s would be required; a total of 12 outputs across the 2 devices. The down side is that more control inputs are required.

If you are interested, a selection widget is available at: http://www.ti.com/lsds/ti/amplifiers-linear/integrated-motor-driver-products.page This helps guide you to a device that meets your needs.