How to set reference voltage RAMPS 1.4/a4988?

Hi!

I'm setting up a new system. My first. I have Wantai 42BYGHW811 steppers 2.5A. and a new Ramps 1.4 and a4988s. I was told:

"These steppers are very good and can handle quite a lot of current. For setting up I always measure the reference voltage on the A4988 module and set them to be 0.45V, this will give you a good starting point for all the axis, it's possible you need to turn it up a little more for the extruder to get some extra force and quick retraction.

But start with 0.45V and all the motors should run just slightly warm, not hot. Don't run motor's too hot."

I have a multimeter. Can some explain how I can set the REFERENCE Voltage properly?

Thank you

Maxi

Easiest way: Connect one lead of your probe to ground. Connect the other to a small metal screwdriver. Turn the pot on the A4988 board until your multimeter reads 0.45V. Be very careful not to short anything with the screwdriver. RAMPS can be connected only to USB for this, and it is recommended that 12V be disconnected to help avoid shorts.

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Quick questions:

1) Do I need to load firmware to the Arduino to be able to adjust the driver's voltage?

2) So, no 12 v power, just the USB 5v from the Arduino?

3) can this be done without the motor attached?

4) I looked at the photos but they are blurry. The multimeter gets ground from the rail. and the red probe goes where? In the photos it is not the Pot?



Thanks

Maxi

I would ignore the picture at this point.

If the pots have a metal screw, you can usually use that part to do your measurement.

If not, the pot will have 3 pins; 2 pins on one side, and 1 pin on the other. You want the one all by itself.

disneytoy Wrote:
-------------------------------------------------------
> 1) Do I need to load firmware to the Arduino to be
> able to adjust the driver's voltage?

No.

> 2) So, no 12 v power, just the USB 5v from the
> Arduino?

Yes.

> 3) can this be done without the motor attached?

Yes.

> 4) I looked at the photos but they are blurry. The
> multimeter gets ground from the rail. and the red
> probe goes where? In the photos it is not the Pot?

As Cefiar said, you can use the pot to do the measurement if it is metal (they usually are).

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Thank you. The pot is indeed metal. I've just studied theory so far. This is my first hands on, and so many warnings about blowing these chips. i thought from reading to NEVER use a metal screwdriver/ I need a ceramic one which I don't have.

wishe me luck:-)

disneytoy Wrote:
-------------------------------------------------------
> i
> thought from reading to NEVER use a metal
> screwdriver/ I need a ceramic one which I don't
> have.

You can use a metal one, just be very careful not to short anything.

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Thanks. Just don't want the magic smoke:-)

Just curious, What would happen if I did short the potentiometer screw on the pololu step stick to something (say a nearby surface mount resistor or cap) while it was powered with 12V. I actually did this yesterday. Now the LCD screen is blank white (full on) with the external power supply switched on. With USB power ONLY, the LCD screen works fine but is dimmer than usual. Also, The arduino board stops getting thermistor readings with the power supply plugged in AND therefore gives the MINTEMP error. However, thermistor readings work when powered with USB. Anybody got a good idea on how to diagnose this? I know its not the RAMPS because I tried using another RAMPS board and it has the same problem. I'm using the DCcduino MEGA 2560 chinese replica DCcEle. Voltage regulator maybe?

Edited 3 time(s). Last edit at 09/05/2015 02:27AM by hedron.

You get wrong measurements if you only use USB power. Power the ramps properly with 12v as it is supposed to.

Dont know why other People's renommend as they do, as it will lead you wrong.

Look af the section configuring vref
[www.instructables.com]

Edit
You properly ruined a driver. Try removing it. With ALL power sources turned OFF

Edited 3 time(s). Last edit at 09/05/2015 03:31PM by dintid.