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Troubleshooting - PMinMO.com

Troubleshooting

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General Troubleshooting DIY Boards

In general the place to start is to check all solder joints with a magnifying glass, it's even a good idea to do that before applying power to a board. Power up the board not connected to anything but power for the first time. When powering up a board, check to see that the regulator is supplying the proper output DC voltage. i.e. where used, 5V, 3.3V, 12V etc. Checkout each board individually and verify they work before starting to hook up the system.

Simple DIY Stand Alone Driver Troubleshooting

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Depicted is two simple hookups to test a motor driver board independently of the PC and interface board. When building a system it is simplest to break down the system into logical blocks to troubleshoot. In the below picture S1 and S3 simply serve to enable the driver board and switch directions, they can also be hard jumpers instead of switches. S3 is a normally open pushbutton switch. When everything is working correctly, with S3 closed, pressing switch S2 should give you a step or two on each press. It may also give steps when your release the button. Switches often have contact bounce. Contact bounce is when the contacts make and break quickly as it starts to make contact or starts to break contact.



System Troubleshooting

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After you determine your drivers are working, you can go to the next level and incorporate the interface wiring back to the PC and one driver board. Start with the driver hooked to the X axis and check to see that you can jog the motor on the Y axis both directions. At that point you know you have the software correct and one working axis in a configured system. Remove the driver and connect the next driver to that same X axis connector on the interface board and jog it both directions. Do that for each driver board. Once you have verified all elements work on on axis, move to add a second drive to the Y axis in conjunction with one driver on the X axis and jog both motors. If there is a problem, in all likelyhood it's a software setup problem.



Testing the Motor Outputs of a Bipolar Driver (L297-8, A3977)

A quick check for outputs of bipolar drivers is to configure the board as full step, and temporarily add a high value (1K) resistor in place of the motor phases. With power and the board disabled, using a dc voltmeter, measure the voltage from each of the four motor outputs to gnd, all four ouputs should be near 0V. Enable the board by applying a gnd to pin 1 of the 10 pin connector. Measure the four outputs, two of them should measure near 0V and two should measure near the motor supply voltage. Pulse the step line and you should see the outputs change, the two that were near 0V should go to near the motor supply voltage and the two that were near the motor supply voltage should go to 0V.


Testing the Motor Outputs of a Unipolar Driver (L297uni, Discrete, SLA7052)

A quick check for outputs of uipolar drivers is to configure the board as full step, and temporarily add a high value resistor (1K) in each of the outputs to the power supply positive. With power and the board disabled, using a dc voltmeter, measure the voltage from each of the four motor outputs to gnd, all four outputs should be near 0V. Enable the board by applying a gnd to pin 1 of the 10 pin connector. Measure the four outputs, two of them should measure near 0V and two should measure near the motor supply voltage. Pulse the step line and you should see the outputs change, the two that were near 0V should go to near the motor supply voltage and the two that were near the motor supply voltage should go to 0V.

Tachus24 3 Axis Board

A quick check for outputs of this board is to temporarily add a high value resistor (1K) in each of the outputs to the power supply positive. With power applied, using a dc voltmeter, measure the voltage from each of the four motor outputs to gnd, two of them should measure near 0V and two should measure near the motor supply voltage. Pulse the step line and you should see the outputs change, the two that were near 0V should go to near the motor supply voltage and the two that were near the motor supply voltage should go to 0V.


Troubleshooting the 3 Axis Tachus42 Board.

L297-8 (Commercial NOT DIY L297-8

[L297-8]

Logic Probe

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Several of the PC boards on this site have a troubleshooting logic probe built into them. In the simplest form a logic probe is a visible indication of a logic state. Logic levels vary based on type of logic used. Virtually all of the boards on the website here use TTL level logic signals. Voltages less that .7V is considered a logic Lo, voltages greater than 3.3V is considered a logic Hi. For example if your X axis motor isn't changing directions assuming that the software is configured that pin 3 of the PC's parallel port is configured for X dir. With the system powered up and the software running, jog x one direction then the other. Starting at pin 3 of db25 on the interface board, check the signal with the logic probe. If it LED toggles on to off and back as you jog back and forth then the signal is present there, and the software is configured properly. Next move the probe to the direction input on the motor driver board and repeat the jog. Again the LED should toggle from on to off and back as you change directions on the jog. You can test an enable signal by the same method. Also you can monitor some pulsed signals such as the step signal. Fast pulses will vary the intensity of the LED depending on the duty cycle of the pulse. If you have a narrow step pulse such as 5us, and a step rate of 1khz. You may barely see the LED illuminate when pulsing. If your software allows, set the step pulse width to 50% of the pulse rate. At 1KHZ that is a pulse period of 1000us, so set your pulse width to 500us. A simple logic probe can be made out of 2 resistors a transistor and a LED. It can be made more useful by adding a third resistor. See illustration below:

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