Hello all,

I'm trying to build my own version for a 3 axis CNC with arduino.
For the start I'm using the diagram bellow. What is the 10K resistor doing in the circuit and how it should be connected?

 

That is a pull up resistor on the EN net. Connections are as shown.

Do you understand schematic net names and how they show connections without lines?

 

That is a pull up resistor on the EN net. Connections are as shown.

Do you understand schematic net names and how they show connections without lines?

Hi Ernie, to be honest I don't think I understand. Pin 8 from arduino goes to the EN of A4988. I don't where to introduce Disable Drivers bit.

 

Hi Ernie, to be honest I don't think I understand. Pin 8 from arduino goes to the EN of A4988. I don't where to introduce Disable Drivers bit.

If this is your own version it seems strange that you are not intimately familiar with your own design. Oh...OK, you got the schematic from somewhere and you are going to build a copy. One or more.

Here is the deal. If the signal EN is not connected to anything then the resistor will set the value at a logic '1'. I'm not familiar with the particular chip so you will have to tell me if that means the chip is enabled or disabled. If the signal EN is connected to a driving source then that source must pull the EN signal to a low or logic '0' state to do the opposite of what the pullup resistor is doing. The reason we have to do this is that in most logic families a logic input has no defined state. It could be low or logic '0', or it could be high or logic '1', or it could inhabit a metastable no man's land where it wanders back and forth between states. Such oscillatory behavior is inimical to the proper operation of the device.

 

In a schematic like this, every "net" has a name, the nets with the same name are all connected together.

"EN" goes to many points in this circuit, imagine how messy the drawing would look if you connected them all with lines.

The 10K resistor goes between two nets: "5V" and "EN" - it's a pullup for the "EN" net.

 

The EN to the Arduino is just the 10k pull up to enable the drivers, the EN would then normally be taken to a terminal that would take it low for external disable.
That is the common way of doing this.
Or this logic could be opposite, low to run.
Max.

 

Thank you all for help.
The diagram is from http://blog.protoneer.co.nz/arduino-cnc-shield/arduino-cnc-shield-scematics-v3-xx/ . Is not my design, sorry for not mentioning.
Please see the image bellow same board same site but this time some connections are made without the pull-up resistor.

 

That shows the drive enable is done through the Arduino rather than external.
Which I see now I missed on the first version.
Max.