Adjusting motor current/voltage

X-Carve Troubleshooting
41

Larry,
Many many thanks for your assistance. I will be setting up a load circuit to set things up ‘properly’ because I suspect that this is something that is causing a large number of people problems - the forum has many faults that look very similar to my problems with incorrect pot settings.

A simple way of adjusting these pots looks like it would solve many of these problems.

In the interim, I’ve taken the easy path and simply adjusted things by ear while air-carving. Hardly scientific, but not something that’s likely to damage anything.

Re your fan comment, should the fan ‘suck’ air from my enclosure or blow air into it? Mine draws the air out of the enclosure (away from the card), but this seems less effective than blowing air directly onto the chips on the board. Are these fans DC (can I swap the wires over to reverse the direction) or is drawing air away from the card the way these things are normally setup?

Regards,
David.

42

It shouldn’t matter which way the air is moving, thermal transfer is more dependant on air flow.

That being said, for both set up so work properly there should be outlet/inlet vents to allow the air to move through the enclosure.

43

Hi, David.

I don’t have any information to back me up, so my thoughts are just that, my thoughts. Let me just put those out here and then you can decide whether or not they have merit.

Heat, like most things that flow, take the path of least resistance.

Temperature likes to be uniform. If you put two objects of different temperatures together and leave them that way, over time, the temperature of the objects will move toward each other’s temperature until they match (assuming no other outside influences).

Heat rises in air. As the air above an object heats up from that object a small convection current will flow in the heated air moving the heat up and away from the object.

It’s really a lot more complicated than this, but this is enough to get the point across. So, there is no simple answer.

Scenario one: The power supply doesn’t have enough air flow to move all the heat it generates away from the power supply so some of it moves up into the electronics sitting on top of it. The electronics generate their own heat and add to the problem. If you have the electronics fan blowing out then you draw more of the excess heat from the power supply over the electronics causing the air flow across the electronics to heat up more than if you had the electronics fan blowing in to counteract this additional heat. This assumes the fan is moving enough air to overcome the rising heat and remove the heat generated by the electronics.

Scenario Two: The power supply fan is sufficient to move all the power supply heat out the end of the power supply away from the end of the power supply where the electronics are mounted. In this case the fan blowing out would aid the natural flow of heat giving you the best cooling situation. In this case the fan blowing in would be bucking the natural flow and could cause a reduction in cooling.

So, until I get my X-carve (it was supposed to ship today, but got caught up in the parts problem) I can’t test any of this.

My initial thought is that I will most likely start with the fan blowing out until such time as I can test it to see if the direction makes any difference at all.

Basically Rusty has the answer, you need sufficient venting and enough air flow and you can overcome most heating issues.

If the fan moves enough air it could be a moot point.

44

One other thought.

If your electronics are close to the X-carve you would probably get less debris in the electronics if the fan is blowing out.

1 Like
45

Thanks Guys,
Might add a few more vent holes and put some kind of fine mesh over them. Pity nobody wears pantyhose anymore.

1 Like
46

We were discussing this many years ago in the class room, I always remember what Prof. Said, " heat is sucks for electronics, you have to suck the air out". You’re correct Larry, blowing directly to heat exchange sensitive chips, cause more problems. Every Advanced electronics enclosures have slow running bigger fans sucks air out.

47

Thanks Alan.

48

Hmmm.

Had still been losing X axis position randomly - found the grubscrews on the stepper motor pull had come loose just enough to slip under load… Do’h!

Dewalt router hanging on the front now - fantastic sawdust making device. Highly recommended upgrade…

1 Like
49

does any one have any ref voltages for a 1000mm machine, with nema 23 steppers, and dewalt 611 router?

thanks

50

Check this thread:

51

Would you all think this issue would be synonymous with needing to increase current to Y axis stepper motors?

IMG_3479.JPG2654×1770 2.09 MB

52

That looks like some missed steps. Did your belts let go, or you pulley slip on the motor shaft?

53

I noticed it seemed like the machine was moving a little bit jerky, intermittently. I suppose it may have been missed steps, but considering that the axis it would needed to have failed on is the one with two parallel motors working in unison, it just seems… odd. I’ll try tightening the set screws and try it again. Thanks Rusty.

P.S. it also might be worth noting that this happened immediately after reducing the spindle speed on my Dewalt 611 to 1 or 2 from 3 or 4 because I smelled something burning. I thought it might have been the wood, so I turned it down.

54

The two motors working in parallel are both hooked to one stepper driver chip so each motor only gets half the current. This could be a current limit setting problem on the Y axis. If you look at the current limit potentiometer for the Y axis as if it were a clock face what time would the current limit setting be for the Y axis? I would expect it to be somewhere between 11 and 12.

55

Intermittent jerky movements could point to thermal shut down of the driver chip, although once it hit the point it usually doesn’t stop until you reduce/raise the current.

56

Could you explain how thermal shutdown actually works? Is it the g-shield overheating or the motors?

I have always wondered if I could crank the pots and just keep the g-shield cooled by a large fan. Obviously that’s not great for my motors, but just the concept confuses me.

57

I think the thermal shutdown actually refers to the driver chips getting too hot. If you’re using Nema 23s the gshield can’t output enough current to over load the motors, so you shoud be fine there (don’t quote me on that). I’d check out @RobertA_Rieke video about adjusting the pots, you can see what thermal shutdown actually looks/sounds like.

Hope that helps!