Re : Re: Re : Need DIO for 3.3V outpus

[Rafi2003]

HI,

Please help me to select a DIO card.

The application actually requires only outputs, but the circuit uses only LVTTL (3.3V)

I need 24 or 32 outputs, very low frequency.

Natuarally, I'm looking for a cost effective solution.

Thanks

Rafi

[JB]

• USB-6009 (12 DIO)
• USB-6501 (24 DIO)

would be a good choice like mentionned here.

Message Edité par JB le 02-21-2008 06:21 PM

[PhillipBrooks]

I think Rafi2003 is looking to source 3.3 volts to control a low voltage device. The 6009 and 6501 are 3.3v tolerant for input, but I think they only output 5.0v.

I was recently asked to change from 5.0v to 3.3v on a project, and the choice was between replacing the NI cards with much more expensive boards (>$1,000 US) or placing TTL/COMS level shifters on the other side (FPGA). The solution was to level shift on the custom electronics side.

[PhillipBrooks]

See this KnowledgeBase entry:

3.3 Volt TTL from Digital Products

[JB]

Hi Phillip,

Thank you for joining us in this thread. Your comment seems not to be corret for the USB-6009. Extract from page 22 of the user manual :

The NI USB-6009 ports can also be configured as active drive using the
NI-DAQmx API, allowing 3.3 V operation with a source/sink current limit
of ±8.5 mA. Refer to the NI-DAQmx Help for more information about how
to set the DIO configuration.

Therefore 2 USB-6009 could be a low cost alternative to an expensive card.

[PhillipBrooks]

My system required 60 output lines and I use the 6509; and the original poster asked for 24-32 lines. I suppose he could use multiple 6009s (12 lines each) to reach the line count needed.

Good to know that the 6009 can source 3.3 V, I might be able to use that for bench tests.

[NI-Bongo]

Hello all,

Both the 6501 and the 6009 can be configured to output 3.3V in software.  The following articles describe how to do this.

Digital Output Drive Type for the NI USB-600x Devices
http://digital.ni.com/public.nsf/allkb/D2C0A1087F635A6B86257090006A382C?OpenDocument

Configuring the NI-USB 6009, 6501, and 62xx to be Open-Drain or Push-Pull
http://digital.ni.com/public.nsf/websearch/D9B4018C3E540CE4862570F30068C0DB?OpenDocument

Since both devices are bus-powered, make sure you won't exceed the current specifications for the devices with your application.

Let me know if I can help you further.




Message Edited by NI-Bongo on 02-22-2008 02:04 PM

[Rafi2003]

Thanks John, Philip and JB for your answeres,

While considering your suggestoins I'd like to ask for your openion on the 6527 as an option for my task.

This card uses isolating circuit  and I wonder if it could use 3.3V on the application circuit,

Refering to page 3-11 on the 6527 User Manual, there's an example of how to connect the isolated output to a 5V external supply with a 5Khm load resistor.

My questions is if same circuite can be used with 3.3V supply and 3.3Khm resistor?

Thanks and regards

Rafi

[JB]

As mentionned on pages 3-10 and following of the user manual, the output channels of a 6527 are solid-state relays containing a
LED and two MOSFETs connected together to form a bidirectional switch.

1. Depending on how the load is connected to the terminals, an output can either source or sink currents.
2. As you know, the output levels depend on the external circuit (schematics on page 3-12). You only have to connect the pull-up resistor to an external 3.3V power supply to get a 3.3V compatible output. One limit is the maximum output current (120mA on page A-2) and the total power consumption of the interface.  But there is not the least problem with 3.3V and 3k3. The value of the resistor is not critical because you are far away from the max current !

Message Edité par JB le 02-25-2008 09:29 AM

[Rafi2003]

Hi JB

I coclude that for my application (24 output lines to control 3.3V circuitry, slow rate) I can either use the PCI-6527 or the USB-6501.  The price difference is $660 vs $110 and the PCI needs a much heavier cable. 

It seems that the USB-6501 is a better choice in this case. 

Any feedback?

Thanks

Rafi