Lineair motion control advice

[Buechsenschuetz]

For most applications it is recommended to use the i/o terminals of the motion controller to switch relays.

Remember the maximum switching capacity of the digital outputs, the max current of the relay must be lower than that value. Also, keep in mind that there is a certain saturation voltage if you use the open-collector (sinking) configuration.

In any case, when driving relays or solenoids, a diode must be connected in parallel (in reverse direction) with the coil to cut down excessive backlash voltage. This applies for small relays, too. When using optoelectronic relays of course you don't need a breakdown diode.

[Jochen]

If you don't need more than 4 outputs, you also could use the breakpoint outputs on your Motion I/O connector (if they are not required for breakpoint operations) This will save you an additional connector and cable. Here are the specs for these outputs:



Please note that you may have to connect an additional resistor between +5V and the breakpoint output to be able to drive enough current (as you can see, there is just a 3.3 kOhm resistor preinstalled on the board).
To set the line states for the breakpoint outputs use Set Breakpoint Output MOMO.flx.

Jochen

Message Edited by Jochen on 10-15-2007 11:22 AM

[Buechsenschuetz]

In many cases it is better to use digital outputs of the NI controllers (dedicated i/o lines or breakpoint outputs) in sink configuration.

If you add a resistor in parallel with the on-board resistor the output transistors will have to dissipate quite a bit of power when they are turned on. It is obvious that there will be a current flowing through the output transistor which has the same value as the output current supplied by the output to the load.

This can be avoided by connecting the load between +5V (an external supply may be necessary since the +5V output of the NI controllers is NOT recommended to be used as a supply) and the output, plus a current limiting resistor if necessary. In this configuration, there will be no current flowing when the load is disabled, and when the load is switched on, the power will be dissipated in the load device.

Anyhow, when using this sink configuration, logic levels have to be reversed: the output must be in logic LOW state to switch on the load current.

[Buechsenschuetz]

PS. When using the SINK configuration please keep in mind that the output transistor has a saturation voltage of 0.6V. So your calculations should be based on an available voltage of 4.4V between a +5V supply and the output. Of course an external +5V supply to supply the sink output must have common GND connection with the NI controller.

[Sjoerd1973]

Thanks again. Sorry for the delay.

I found this phidget relais board. It hardly needs any power so I can think i can connect it direct to the onboard trigger. I willsuply it with it's on 5v powersuply so It only needs 5v to close or open depending on wiring nc or no. Should I put a fuse in the power line to be sure ?

In the example database i found:

1 - momo_software_breakpoint.vi and 2 - momo_breakpoint_dio.vi 

These show how to use the breakpoint lines as triggers but how do I specify if itis trigger 1, 2, 3, or 4 that should be switched to high or low ?

Thanks for helping.

[Buechsenschuetz]

> Should I put a fuse in the power line to be sure ?

Since the +5V supply will flow into the NI motion controller output circuitry it will be no fault adding a fuse. In case of a short in the relay coil excessive current might flow through the output transistors.

Anyhow, you should use the fastest fuses you can get - microfuses are a good option. Usual fuses are much too slow to protect semiconductors. There is a saying among technicians in Germany: "a transistor is the best device to prevent a fuse from blowing", i.e. a transistor usually will burn out prior to the fuse supposed to protect it.

[sun tracking system]

Can I design a stepper motor using Labview 7.1.If yes please give me the code in following address.

From

arijitmtech@gmail.com

[Curious_Mind]

Hi, 

I am using Vexta motor with velmex Xslide along with STM5404 microstepping driver. I have two limit switch at both ends of velmex Xslide.

My DAQ has  pull down resistor and my limit switch is normally closed. How can I wire the limit switch to DAQ so that when motor goes to end, motor stops? And how can I reverse the direction? please help.