If one axis is ‘misbehaving’ (not spinning, missing steps), then you need to isolate the issue. The problem could be:
Before touching ANY of the stepper motor wiring – ensure there is 0.0 volts at TB6 (PRO) or TB5 (EZ). Connecting/disconnecting steppers with voltage on the board is an excellent way to blow a driver chip.
Did you just move/change your system?
For whatever reason, moving or changing your system is a common cause for things to “just stop working”. Triple-check all wiring, especially the stepper motor wiring. Check all connectors, connections and the screw terminals connecting the steppers to the board.
Excessive torque on the small blue connectors on the PC board can crack the solder joint, so if all else fails, check the underside of the board at the connector joints.
Bad stepper / bad wiring
Disconnect the power.
Do a very careful visual inspection of PC board starting at the screw terminals and working ‘inward’. Double-check the wiring from the PC board to the stepper.
- Colors are going to the right wires?
- Connections all solid?
- All wires inserted in the screw terminals are properly stripped ?
- Especially check the solder connections at the screw terminals. Over-torquing can break the solder joints.
At the terminal blocks on the PC board, swap the ‘bad’ motor and wiring with a known ‘good’ motor and wiring. Double-check the wires/colors/order before power-up.
The problem stays with the axis. Now the ‘good’ motor is not working and the ‘bad’ motor is. This eliminates the stepper and wiring from consideration. Jump to Solder / assembly problem.
The problem moves with the motor. If the ‘bad’ motor is still bad, then the problem is in the wiring or the motor.
Swap a ‘good’ motor with a ‘bad’ motor at the motor-end of the cable. If the problem ‘moves’ with the motor – bad stepper. If the problem stays with the same axis – wiring problem.
The steppers will run warm-to-almost-hot. They are turning a lot of current into motion. However they should NOT be hot enough to burn you. If the stepper is running very hot, consider some type of heatsink to dissipate that extra heat.
Make sure your coupler between the motor and the drive screw/belt is not loose and slipping. This can create what looks like “missed steps”.
It is easy to ‘mix up’ the wiring from the steppers to the board. Most likely, the wiring used between the motor and the board has different colors than the motor. To minimize problems:
- Never use wire nuts. They might be OK for a bench test, but NEVER in actual use. Wire nuts are designed to remain motionless for their entire lives, not to be whipping around on a dirty, vibrating mill.
- Wire all 3 (or 4) motors identically.
- Inspect each connection carefully – wires that are not carefully stripped can break, wires can be improperly stripped when put into the screw terminal
- Firmly but gently pull on each wire individually going into the screw terminal to confirm each is properly clamped in the terminal strip.
See FAQ: Do a thorough visual inspection
Check your Power Supply voltage. Do you have sufficient voltage to drive the necessary current to the stepper motor. Low voltages (like 12V) will not provide ideal performance. I’d suggest around 32-36 Volts DC and 7-10 amps (3 motors = 7 amps, 4 motors = 10 amps).
Is your power supply SPECIFICALLY DESIGNED to supply and receive very large current spikes that are typical of driving stepper motors? Just because the power supply is advertised as “36 Volts DC at 10 Amps” does not indicate it’s ability to drive large inductive loads.
PRO: It should be between 12 and 42 Volts DC when the motors are all running. Under no circumstances should the supply exceed 42 VDC.
EZ: It should be between 12 and 36 Volts DC when the motors are all running. Under no circumstances should the supply exceed 36 VDC.
Check microstepping jumpers. If you have no microstepping jumpers installed (J1, J2, J3) on the 8 pin headers (PRO) or 6 pin headers (EZ), then the motor for that axis will not move. You must install the jumpers to enable your desired microstepping. See FAQ Microstepping Configuration.
Disable microstepping (set to 1:1). I suggest you keep it disabled during initial testing and start-up.
Read the FAQ Microstepping. Ensure your software is set to match.
We recommend using 1/2 or 1/4 step. This produces almost full power and usually avoids any resonance issues. The finer the micro step the less power you’ll have.
Do not use microstepping to increase the “precision” of your machine.
Motor current settings
Idle Current Reduction must be disabled PRO board only – install J4 on all the 8-pin headers when setting the voltage.
Re-visit the Vref voltages at the test points where the max current is set for the stepper motors. Compare with the assembly instructions.
You can adjust this setting while the motors are running. If this setting is too low (or zero) the motors will not move reliably or may not move at all.
Use the calculator to the right to determine the voltage that must be present at the small test pad next to the blue trim pot.
Idle Current Reduction
Disable the idle current reduction by installing J4 in all of the small, 8-pin headers (PRO board only). Idle current reduction can cause missed steps in some applications.
Bad driver chip / overheating driver chip
[stextbox id=”info” caption=”The ‘lock-up test'”]With the power applied to the HobbyCNC board, does the stepper motor “lock up”? That is, can you NOT turn it easily by hand? If the motor is ‘locked-up’, then the driver chip is most likely fine.[/stextbox]
Did it smoke? Does it get hot? If you can’t hold your finger in it for more than a second-or-two, then it’s running too hot. Add a heatsink and fan or back-off on the current. The driver chips have a thermal shutdown feature to protect themselves.
Do a visual inspection of the parts around the chip. CAREFULLY inspect all the solder joints on the driver chip. Are all parts installed in the right orientation? No parts burned. No discoloration of the PCB under any part?
More than likely a loose connection did the chip in or a poor (cold) solder joint. Check the terminal block for continuity at each pin. Over tightening the wire screws CAN fracture the corresponding pin.
Did you futz with any of the stepper wiring while the board was powered?
Bad/wrong parallel cable
Not all 25 pin M-F cables will work. It needs to have all 25 pins wired, 1-to-1, or “straight through”. A 25 pin M-F serial cable will not work (see blog post Blown Chip #2), even if it says “straight through” on the data sheet – most serial cables do not have all the pins connected. You can confirm this with steady hands, a volt meter and a paper clip.
Is there something causing binding on that particular axis? Try turning the axis by hand (no power to the motor) through the entire movement range and confirm that everything moves smoothly.
Software sending steps too fast
Slow down the acceleration and velocity A LOT for that axis (like 0.5 IPS / 30 IPM). If it starts working, then slowly increase them until the problem appears. Back off.
Also check if your software can ‘invert’ the step signal. Our boards want “Active High”.
Different movement one direction of rotation vs. the other direction
Check for proper orientation of the RN resistor networks.