DIY Stepper motor output reducer

[Tempy111]

I'll try ^_^

 

[Tempy111]

Oh, just to note, been a minor issue and I'm awaiting on some new parts before I can really do a good test but they should be with me within a couple of weeks.

 

[Tempy111]

taking a little while for the couple of parts so I can test this but.. expected this week, so I can FINALLY test this and get back to you guys.

 

[Tempy111]

Okay.. I decided the best place to put the diodes are between the motor and the driver as there isn't really any space to put something between the driver and the rest of the board. it also allowed me to put something in which wouldn't directly run much risk of damage to the board itself.

then a problem.. it's a 4 pin stepper motor.. so if i'm right, that means two Positive and negative connectors. these are labelled 1A,1B,2A,2B. I think, A's are in and bs are out. So... I would need to put a diode on both As?.. I think so.. any thoughts?

 

[Tempy111]

okay.. forget that.. Of course I can't put the diode on the motor itself like that.. it's coming off the 'b' lines of the motor.. If I remember how these work and i'm probably wrong here.. it has the two windings, one on each side of the motor. basically, power goes from the driver into '1a' through the winding, making the motor turn that way, then out through '1b' back into the driver. when the power goes from the driver to 2a it goes through the winding on the other side, and the motor turns the other way, then out through 2b back into the driver..

when the motor is turned by hand or whatever, it generates a current in the windings and sends that through the b lines unless I know the electricity is being 'used up' in the winding, blocking it from going back to the driver is stupid and useless.. The driver plugs into the board mounted socket.. and making a mid-point socket is.. possible.. but maybe a bit still.. but I guess possible.. just get a bit of prototype board, put a socket on top, going straight into pins on the bottom, and it'll work as a pass-through. adding the diode to the vcc line would be what I want.. since the rest of the board path is printed, it's not really possible to put a diode there...

 

[marconi]

Your stepper motor is bipolar which means current flows in both directions through the coils. A diode in series or in parallel with a coil would prevent bi-directional current flow.

 

[Tempy111]

yep.. When i thought about it, that's what I realised.. gonna need to make a board with a driver socket on top and pins on bottom as a pass through which i can then use the diode on

 

[topquark]

Not sure what motherboard you using here, most folk use something like an arduino with a "cnc" v3 shield and stepper drivers like A4988 or one of the newer Silent TMC2xxx drivers that support microstepping. Do you have a particular need to design this from scratch, IE needing more than just XYZ and extrude?

 

[Tempy111]

The stepper drivers are 'for makerbot' which I think is a Tmc2100 .. I don't need to design them from scratch.. as stated earlier, the issue is the feedback which is generated from any motor when it's turned by hand, in this case, when the carriage or build platform need to be moved by hand when the device is off. this generates a current which is then thrown into the board and cause lead to spikes and the screen, for example, turning on briefly. while this can be partly controlled by being very careful to go slowly when moving, but at times, can be hard to avoid and I was looking in to methods to pretty much remove this from beign a problem. A diode on the power line between the board and the driver was suggested and I was going to try this out, but the first problem, without dealing with bending pins, would be to have some form of 'extension' so the diode can be added without physically modifying the stepper driver or the board itself. I did wonder about doing it between the motor and the driver but it didn't take too long (and was even confirmed) that this was just a stupid idea which wouldn't work anyway. as the Driver pins plug into the sockets on the board for easy replacement, the location of where to put the diode is somewhat limited

 

[topquark]

In which case don't move the platform/head by hand. The unit should be under software control and you can use one of the fast goto GCODE commands to move the platform/head. Alternatively you could use M18/M17 to disable/enable the motors as required before moving the platform/head.

Using diodes will not work for the reasons already stated. You could introduce manual switches (you would need two for each 4 wire bipolar stepper). That, however, would be eight switches to change everytime you wanted to make a manual movement.