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6009 digital input gives output

Unfortunately, the USB-6009 seem to have been a poor choice when you made the change.  What PCI device were you using?  What are the specific requirements for your digital lines?

 

Lynn

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Message 11 of 14
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We made the change from PCI because it limits the number of computers that can be used.

USB is much more convenient, but....

 

We have very modest requirements, 12  inputs (with or without pull-ups) and 10 outputs 0/5 Volts to drive ULN2803 driver inputs.

The ULN2803 is not exactly high impedance, but the 4.7 kohm pull-ups deliver enough current to turn on the drivers (2.6 Volts resulting voltage)

 

 

PS. We use the USB-6501, but I think the whole series have the same stupid pull-up resistors.

 

I will check with other suppliers, Welleman might have something useful.

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Message 12 of 14
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It looks like you have 2 unused lines on your USB-6501. And you probably have some unused ULN2803 sections. Consider setting up one of the unused outputs and 2 ULN2803 sections as an enable controller. Since the DAQ device powers on as an input and the pullup resistors set it high, take advantage of that. Connect the DIO output to the input of one of the ULN2803 sections. Add a pullup resistor and connect that output to the second section. This gives you a non-inverting configuration at the output of the second ULN2803. At power on that output will be high. Connect it to a relay which switches power to all the rest of the devices being driven by the ULN2803(s).

 

Add to your program code which delays changing that DIO line to an output until everything else has been configured and has had a suitable initial value written. Then convert the enable controller DIO line to an output and write a zero to it. That will activate the relay and apply power to everything else.  If needed (and you have an extra unused input), you can configure a power-on reset circuit to monitor the state of the voltage switched by the relay.

 

This will cost only the relay and a bit of time to wire it up and to modify the program. It will allow you to make use of the equipment which you have already purchased at much less cost than buying new DIO devices.

 

If you need higher reliability on the power up sequence, you can add some extra logic circuits and require that the enable DIO line be toggled several times at a specific rate before switching on the relay. If you go this route be careful to consider the timing jitter you will get from the software timed digital outputs.

 

Lynn

 

p.s. Sorry about the confusion on the DAQ device.  I had not noticed that you were not the original poster.

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Message 13 of 14
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Well, a redesign of the (two) pcb's could solve some of the problems, but that won't fix the already delivered units, and the cost of redesigning is also too high since we only sell 5-10 units per year.

 

 

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Message 14 of 14
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