The Linistepper

Carton box to avoid damaging during shipping

The Linistepper is a PIC-powered open source controller and driver for small to medium sized unipolar stepper motors. It offers standard full and half step stepper driving, as well as 6^th and 18^th microstepping. It provides a single wire rotation direction selection, and can be configured to operate with only a single wire that provides the pulses.

The Linistepper comes in a kit. I received the kit in a nice carton box which contained all the parts including the PIC microcontroller pre-programmed, a PCB pre-drilled with green solder mask and white silkscreen with the parts arrangement, with dimensions 70 x 51 mm (1.6mm thickness), and a mounting kit for the power transistors heat-sink. The heat sink was not included (of course). The mounting kit had 4 sets of M3 screws with nuts, plastic insulating washers and mica insulators for the power transistors, as well as a small quantity of thermal conductive paste. Finally, there was a 14-pages manual that gives information for the mounting procedure. The same manual can be found in this link.

All parts needed and a manual was in the box	Nice 2 sided PCB with green solder mask and white silkscreen	Complete insulating mounting kit for the power transistors heat sink

To mount the kit i used a temperature-controlled soldering iron, pliers, wire cutter, screwdriver and a drill with 4mm drill bit. I followed the instructions line by line and measured the time needed to solder all the parts on the PCB. It took me about an hour to finish the PCB. I used the heat-sink from my old P4 without the fan. Normally, it would take a total of 2 hours for an experienced person to have the kit ready with the heat-sink mounted, and checked for errors, ready to be powered.

Needed about an hour to solder the parts on the PCB	I used the heat-sink from my old P4 which proved to be too much for my 1.1 amp motor	Within 2 hours, the kit was ready with a heat-sink and checked for errors.

I ran some tests with different motors to see how it responds. First i used a 12 volts 1.4 amps 48 steps per revolution. As expected, i had lots of vibrations in full and half step operation, which was much better when i turned it to 6^th microstepping. When i turned it to 18^th microstepping, i was rather surprised by the smooth operation of the motor in high speed. In lower speeds, i still had little vibrations and noise, but still the operation was very smooth.

Then i changed the motor with a 9volts 0.95 amperes 24 steps per revolutions stepper. I wanted to test how smooth can this controller run this motor. Although the current of the motor is just 5 mA lower than the tuned current (1 ampere), the 18^th microstepping was not a great success. That is not to be considered as a drawback though, as the motor had only 24 steps per revolution. It had a good torque though.

Finally, i run the most proper test for this controller. I used a 2.8 volts 1.1 amps 200 steps per revolution motor. In low rpm i had still some vibrations, but i suppose that this has to do with the tuning of the controller. In higher rpms, there was almost no vibrations at all. The motor ran very smooth.

The first motor that i ran tests with, had 48 steps per revolution	A hard test with a 24-steps per revolution stepper	Test with a 200 steps per revolution stepper with excellent results.

It was time to see what the Linistepper really does. The waveforms that you are about to see, comes from the bases of the 4 power transistors. My oscilloscope has 4 channels so i was able to monitor all 4 transistor bases simultaneously. At first, a quick look on the full step:

Full step timing	A single pulse

Nothing strange, everything is normal. I did not expect to see something strange after all. So i went to half-step. The maker of Linistepper says that this controller has full torque on half step. You can read more info about this method in this link. Let's see if is does what it promises:

Timing	Single pulse

A quick experiment proved that there is no significant torque decrease in half step.

It is obvious, that in half step, there is not a single on-off rectangular pulse as in full step. And that is exactly what the maker says about this method. I decided to run another experiment, to see if the torque in half step is as high as the maker says that it should be. I put a motor to lift a known weight with full step. Then i repeated the same procedure in half step, and measured the difference. In full step, the motor managed to lift 1110 grams. In half step, it could lift 1020 grams, about 100 grams less. That is about 8% less torque, which is a very good performance.

Time for the microstepping. As they both have the same timing, i will show you one pulse zoomed in the oscilloscope:

microstep 6th	microstep 18th

In microstep 6^th, the step-up of the voltage can still be seen, while in microstep 18^th it is very hard to distinguish the steps. So, the controller does indeed what it promises.

This controller will cost you $35 to get it today from piclist store. But is it the right for you? I mean, there are hybrid chips (such as the Sanyo STK672-080) which costs nearly $10 and needs only 2 resistors and a capacitor to operate, and provides microstep 16^th. The Linistepper addresses to those who:

Has only 1 hole for mounting the PCB on the chassis

The large capacitor is a problem when trying to access the screws of the connectors

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