Digital Outputs On 6025E and Sc 2062 Board

[Mic_Scale]

Hello guys,

I'm trying to send pulses via the digital outputs of port B on the 6025E board. I cannot use the counter because I need to be able to trigger out the signal "softwarely". I'm also using the SC 2062 board to isolate the digital Port B on the board from the outer system, which receives the pulses. My questions are these:

1. Is it possible to use the digital output in this non-statical way ? Meaning, setting the digital channel to High and then quickly to Low to create a pulse.

2. Suppose I can use the digital outputs in this manner, will the SC 2062 support this fast switching ?

I've written a program to do this, but when I connected a scope to the output of the SC 2062 I did not see a pulse behavior, but rather some kind of noise. Moreover, when I just set the digital channel statically to High, the output stayed Low....

Doesn't the SC 2062 transfer the signal in a 1:1 ratio ? I don't know what's going on....

Please help.

[AnalogKid2DigitalMan]

Hi Mic_Scale:

The 2062 is a relay card, you will have to supply a voltage to the COM pole of the relay you are using and the monitor the output from the NO or NC (normally open or closed) relay contact. The 6025 should be able to toggle an ouput on and off at a fairy fast rate through software timing. It is the relay that will limit your switching speed, 30 to 60 times a second, I suspsect. I would suggest you read the section of the manual covering the 2062.

I did not get a chance to look at your vi

[Mic_Scale]

Thanks, AnalogKid,

I have gone through its manual but, I thought that the Com pole is for ground.... I though the SC 2062 gets the High voltage from the 6025E. So you tell me that I need to connect the Voltage source to the Com ?

That may explain why I have gotten nothing on the scope after switching from Hight to Low... the Com was connected to ground.

Isn't there a way to isolate a digital output and be able to have high switching rate ? Suppose you want to output a counter with a clock rate of 100kHz ?

[AnalogKid2DigitalMan]

Yes, that would explain your results on the oscope. Think of the relay and it's 3 terminals as a switch which has a normally closed contact and a normally open contact. The COM terminal is common to the other two. When the output is commanded OFF, you will have a closed switch between the COM and the NC terminals. When the output on ON, you will have a closed switch between the COM and NO terrminals. You have to supply the voltage you want switched and typically connect it to the COM terminal. I suggest trying it out with the scope to experience it first hand. Due to mechanical interia, mechanical relays of this sort can only switch so fast. Not possible to get anywhere near 100KHz (maybe 100Hz)

The digital outputs on the 6025 are not contolled by any on-board timer, so the only option to use those is using software timing in a while or for loop. But loops can only execute so fast, this may get you inot the KHz range. But Windoze timing uncertanties will probably yield you a frequency that is unstable.

I would suggest using one of the 2 built in timer/counters on the 6025 to generate a very accurate and stable pulse train. I have used this card in the past to control a high power laser. For it I used and opto-isolator chip between the DAQ card and the laser in case the laser power supply failed. Worked like a charm. I don't believe the counter signals get routed through to yhe 2062, you will have to get the manuals out and figure which pins the signals come out of. There are shipping examples within LV to generate pulse trains with the 6025.

Good Luck, let us know if you need futher help.

AK2DM

[Mic_Scale]

Thanks, AnalogKid,

it's been very helpful.

Would you mind sharing what kind of opto-isolators you have used to be able to output this high rate clock  ? Currently I'm using also the SC 2060 opto-isolator based board, for inputed digital signals, but as said, those are input....

Thanx again.

[AnalogKid2DigitalMan]

Almost any garden variety opto will do, I have used these Avago (was an Agilent part that used to be an HP part) optos before with no problems.

http://www.avagotech.com/pc/downloadDocument.do?id=4829

Please refer to the above datasheet/ app notes, for reference, I used 6.2K/22pF on input pin 2 and the 1K internal resistor on the ouput side, pins 6/7. You may want to adjust for your specifics as needed and view output waveform with a scope. Thae 6025 counter was able to directly drive the diode with the 6.2k in series. I used an external 5V supply on the output side to provide isolation.