3-Axis Stepper Controller

[MP]

1N4001, 1N4002, 1N4003, any of these will be fine as long as the watt rating is ok with your circuit.

MP

[alberto]

MP i see yours schematic but i have a question:
when i connect the circuit, a wire is the signal from lpt port but when i put +12volt and gng from power supply, i must connect also the gng lpt port to the power supply ground or it is a separete circuit with only +12 and gng of power supply and just lpt signal pin without lpt gng?
wich modify if i have 28.2 volt? as power supply?
I'm sorry but i'm not very good in electronics....

[MP]

Hello alberto,
You will want to connect the ground of all circuits to the same "common" connection. The drawing I have posted is for a relay which uses 12 VDC for the coil. If you have a relay that will use a different value of power, then you will want to change accordingly. Please note the current and voltage capability of the transistor you are using.
I can't think of anything in a digital circuit which would need a 28 volt power supply. Why don't you use a smaller voltage? Do you have a device which needs this voltage level? Is this the voltage required for your stepper? If so, perhaps you could tap a lower voltage from a resistive divider. For example, if you are using a current limiting resistor for your stepper motor, you could use two resistors which make up this same value and tap 12 volts from the point where the two resistors connect. Such as this:
28V---/\/\/\/-+--/\/\/\/----MOTOR
^
12V
Or better, make a divider that will give you a little more than 12 and run it through a regulator such as 7812 and some protection diodes to keep it clean from the motor.


MP

[alberto]

Mp thank you! I have made with fidocad a simple relay board trought your schematic. I think it wil be usefull to the comunity.
I hope that there aren't mistake!

RELAY BOARD
COMPONENT LIST:

R.1-4 4.7K
R.2-3 47K
R.5-6 560
D.1-2 1N4001/..02/..03 (see if the watt rating is ok with your circuit)
D.3-4 5mm LED
U1-2 2N3906
Relay1-2

[MP]

Hi Alberto,
Please check the resistor locations. One is correct with the schematic but the other should be connected from base to emitter.

MP

[alberto]

Thank you MP this is the ultimate version. you think that the relay status LED schematic and resistor value are correct?

[MP]

Looks much better! The only thing I am not sure about is the LED. The LED drop down resistor is going to interfere with the coil resistance of the relay, depending upon the value. You will have this resistance and the coil resistance working in parallel. If you look at the parallel formula for resistors, you will see how you are changing the on/off characteristics of the relay by doing this. I do not know if this is a problem. It depends upon the coil resistance for the relay you are using. You might want to connect this status LED somewhere else where it will not effect the relay. This way, if you use different relays you will not take a chance on having a future problem.
You should figure the resistor value from the forward voltage of the LED. 560 seems a little low for this amount of voltage. It will be nice and bright. What is the Maximum current rating of your LEDs?

MP

[alberto]

MP i copy the schematic of status LED in this site (SUB RELAY BOARD) if you think that there are problems the article must be correct. But probably is my not good electronics.

[MP]

I think that article will be fine if you choose the right relays and the right LEDs. Unfortunately, the article did not list part numbers, so you do not know what they had in mind. It all depends upon the relay coil resistance and the current MAX rating of the LEDs.

MP

[alberto]

Dear MP i have built the relay board and it work well, but i have a problem:
mine 3-Axis stepper controller board work at 26.2Volt (20-1.4*1.41) and my electric trasformer(20V 3A) have just one secondary.How can i take 12V to power the relay board and a little cooler fan (12V 2.3W)?
I must buy a little transformer (12v-500mA ex.) to power them or there is a solution from 26v to 12 volt?
???

[MP]

Alberto, you can add a 12 volt regulator to the circuit if you find one that is rated above your output voltage.

Another way to step down the voltage is with non polarized capacitors on the secondary output of the transformer. You connect capacitors in series across the secondary of the transformer to make a voltage divider. If you connect two 100 uf capacitors across a 20 VAC secondary, you will have 10 VAC at the point where the two capacitors are connected in series. You can use different values of capacitors to change the proportion of the divider. In series, the voltage across each capacitor is inversely proportional to it's value. The smaller capacitor has the larger proportion of the applied voltage. Experiment with some values on your workbench. You should find a solution. Don't forget, you are still working with AC, so the voltage will need to be rectified to DC.

MP

[GreekPIC]

Ok, I built the circuit and it worked fine. I had only one UCN so I tested only one axis with TurboCNC, other than that it's ready.

Just one question: when the motor is not moving one coil is still energized. This is probably normal and supposed to provide holding torque but the motor is warming up. Is this normal?

[MP]

It is normal for steppers to run warm/hot. You will notice that the motor, when it is not moving, is in a locked position. Otherwise it would not be very good at holding a step.

MP

[GreekPIC]

Ok, thanks, I downloaded the motors datasheet and it's good for 24V so no problem. I'm using 12V right now but I have a 18V PS I might use.

Now I have to make the relay circuit to turn the spindle on.

PS. Looking back at the thread I saw I have made a mistake in the coolant discussion. The 220 grade oil is used on the slides and is not water soluble. We use Castrol Superedge 33 (~8% in water) as coolant.

[GreekPIC]

Yesterday it worked, today it doesn't! The motor has holding torque but is not moving. What could that be?

[MP]

Can you post the schematic? Or did you use the one in the projects section for this chip?

MP

[GreekPIC]

I used the schematic from the projects section. I didn't change anything between the two runs. The voltages are ok.

Only thing I can think of is that the IC burned. But I only used the circuit for 10 minutes and the IC didn''t get hot (I didn't have a sink so I checked frequently).

I've ordered the rest of the IC's (I tested only one axis), I'll swap this one and see what happens.

[MP]

Usually when the chip goes bad, the holding torque also goes away. How are the pulses on the step pin?

MP

[GreekPIC]

I have to check it out. I was thinking that maybe something is wrong with the software (TurboCNC) or the printer port. I'll probably make a 555 based circuit to give pulses for testing.

[MP]

I agree. Both of these items could cause your steps to fail. On the other side of the spectrum, if your pulses are too fast you would get the same result. In this case, all you would need is to slow down the steps in the software. Hope it is a simple fix.

MP

[GreekPIC]

Ok, working now. I don't know what was wrong because I changed more than one thing (not good, I know). I increased the pulswidth in Turbocnc, changed the mode to 2-phase (jumpers) etc.

I still have to play with the feedrate settings to see what's the top speed I can get out of it. I also found out that I have to redesign the bearing housings because the gears bind at high speeds. The placement is critical so maybe I'll have to make the housings adjustable.

[MP]

I have noticed that some programs are very dependent upon the processor speed of the computer you are using. In this case, it is trial and error until you find the perfect speed.

Are the bearings manufactured by you or is it something you had to purchase? I was curious about the binding. I have an XY table that I just used threaded rods attached to the stepper shafts and nuts clamped to a mount on the table. There is no bearing on the end. It sits freely in the air and there is never a problem with binding. The weight is supported by slides such as drawer slides. Problem there is finding some which are made well enough to give you whatever precision you are after. You have to find a set that does not have too much play.

MP

[GreekPIC]

I use roller bearings in DIY housings (see pic). The problem is that the distance between the motor gear and the lead screw gear has to be set precisely. I decided to ditch this setup, however, for the following reasons:
1. The binding problem
2. I don't need reduction, the motors seem to have enough torque so no reason to loose speed
3. More backlash problems
4. K.I.S.S.
So I decided to go with direct drive.

I received the rest of the UCN's and connected all motors. I also connected home and limit switches and they are working great. Now I have to make the relay board. A question here:
If I make the PNP version won't the motor start if the PC shuts down? I think I'll make the first version.

[Mikromike]

Hello: I starting to build this 3 Axis controller and was wondering if it

[MP]

If I am looking at the same schematic as you, then C2 is a 10 microfarad and C3 is a 0.01. These are by-pass caps to keep the DC voltage smooth. I recommend that you use the better caps (and the correct values). The only problem you will have if you do not is a little noise in your circuit, which might interfere with the precision of the steps.

MP