I recently purchased 6x NEMA 17 42HB34F08AB for my Rubik Cube Solver robot. On the webpage they said they are rated for 1.33A/phase current but while I try to measure the current underload I got 0.25A max. I don't know where does this problem come from or what am I doing wrong. I am using A4988 drivers and the potentiometer isn't changing the current at all. The steppers were working okay but the problem comes from the fact that after a while the arduino jumpers started to burn the plastic. I plugged the power supply (12V 8.5A) cables to back of a breadboard (see in picture). Could it be the cause of the problem? If so is the only other solution to make my own PCB?
Breadboards are for low power logic circuitry and the tracks cannot handle motor currents. They tend to burn and that leads to bad connections, which in turn can instantly destroy the motor driver.
You need to solder all motor and motor power connections to the driver, or use screw terminals if provided. Another option is to use a solderable protoboard (see photo below), with either solder connections or MALE header pins for the motor and power connections.
The motor current is highly dynamic and cannot be measured using a multimeter.
Once you have replaced all the motor and motor power connections, follow the directions to adjust the motor current on the driver, taking into account that the Vref value depends on the current sense resistor value. See the motor driver data sheet for the details.
Five phase motor driver on an Adafruit protoboard:
bobthefakebuilder:
I recently purchased 6x NEMA 17 42HB34F08AB for my Rubik Cube Solver robot. On the webpage they said they are rated for 1.33A/phase current but while I try to measure the current underload I got 0.25A max.
Please show the circuit diagram in which you measure the current.
Be VERY CAREFUL never to connect or disconnect the wires between the motor and the stepper driver while the driver is powered up. The driver will be instantly destroyed.
The tracks in a breadboard are not designed to carry currents measured in amps.
Have you correctly adjusted the current limits on the A4988 drivers?
The Pololu A4988 web page has good info about adjusting the current
I plugged in just one stepper and measured it for you. The Voltage between potentiometer and ground and current running trough the circuit, hope I did it somewhat right. Hope you have a great day.
jremington:
Breadboards are for low power logic circuitry and the tracks cannot handle motor currents. They tend to burn and that leads to bad connections, which in turn can instantly destroy the motor driver.
You need to solder all motor and motor power connections to the driver, or use screw terminals if provided. Another option is to use a solderable protoboard (see photo below), with either solder connections or MALE header pins for the motor and power connections.
The motor current is highly dynamic and cannot be measured using a multimeter.
Once you have replaced all the motor and motor power connections, follow the directions to adjust the motor current on the driver, taking into account that the Vref value depends on the current sense resistor value. See the motor driver data sheet for the details.
Five phase motor driver on an Adafruit protoboard:
Hi,
I looked into your reply but have already filmed a video of me measuring everything under the load. I posted a two videos in replys. If you could just look at them and look if there is some kind of mistake or the only thing I need to do is either get PCB done or the other method you mentioned so that I have no other problem getting all together working.
Thank you for your help hope you have a great day.
Robin2:
Please show the circuit diagram in which you measure the current.
Be VERY CAREFUL never to connect or disconnect the wires between the motor and the stepper driver while the driver is powered up. The driver will be instantly destroyed.
The tracks in a breadboard are not designed to carry currents measured in amps.
Have you correctly adjusted the current limits on the A4988 drivers?
The Pololu A4988 web page has good info about adjusting the current
Hi,
I measured the voltage in the video. If you had time to look at it I would greatly appreciate any criticism as to what am I doing wrong etc.. None the less thank you for help and time
Hope you have a great rest of your day.
bobthefakebuilder:
I measured the voltage in the video. If you had time to look at it I would greatly appreciate any criticism as to what am I doing wrong etc
The problem with your videos is that I have no idea what you were doing in them. The camera is too far from the action and it is impossible to know how connections on a breadboard are made just by watching a video - even in close up.
Please provide the diagram I asked for in Reply #2. A photo of a simple pencil drawing will be best, even if you are not a good artist.
Robin2:
The problem with your videos is that I have no idea what you were doing in them. The camera is too far from the action and it is impossible to know how connections on a breadboard are made just by watching a video - even in close up.
Please provide the diagram I asked for in Reply #2. A photo of a simple pencil drawing will be best, even if you are not a good artist.
...R
Here is the diagram hopefully it's gonna be more helpful than the videos. I put a amperemeter where I have been measuring the current.
If the A in your diagram is the location of the ammeter then it is completely in the wrong place. That is the location where you would measure the voltage between the positive and negative power supply lines.
To measure current your ammeter must be in series with the power, not parallel to it. However measuring the current flowing from the power supply is not relevant because it gets chopped up by the A4988.
If you FIRST DISCONNECT THE MOTOR POWER SUPPLY you could connect the ammeter between the A4988 and one end of one of the motor coils. These connections MUST BE RELIABLE so there is NO possibility of them coming apart. If you break the connection between the driver and the motor while the motor power supply is connected the driver will be destroyed instantly.
If you have everything connected securely then you can connect the motor power supply and measure the current flowing in the motor coil while the motor is stationary. Do not waste time trying to measure the current while the motor is moving. For that you need an oscilloscope.
IF YOU ARE IN ANY WAY UNCERTAIN about what I have suggested then DON'T DO IT. There is a too great risk that you will damage your stepper driver.
If you placed a current meter across the supply as indicated, you would have likely shorted the supply and
blown the meter's fuse.
Current is a flow, not a potential, so the meter has to go in-line with the flow, not across two terminals.
If this is how you connected it and only saw 0.25A, then there must be a lot of resistance in the wiring,
suggesting the hook-up wires you used are only good for signals, not power.
