How to build a custom light with NI 1742 Smart Camera

[coolrthancoolio]

I need help on how to build a cuircuit for the NI Smart Camera 1742. I have been searching online for possible ways to get it to work but I have fried a bunch of LEDs and Resistors.

It has a continous current source of 50-500mA.

So things I have tried with a paralell LEDs:

I have tried using a 100 Ohm resistor in parallel with the current and the resistor would get really hot but still no light. ( We tried converting the current source into a voltage source)

I have tried putting LEDs in series with 100 Ohm resistor and it burnt out the LEDs.

We tried doing a voltage divider with a 100 and 10 ohm resistor and burnt more LEDs.

Currently we cannot afford an expensive light for our project. so we are trying to make our own. Thanks...

[Z'atari]

Hey coolrthancoolio,

Make sure you are following the setup detailed in the manual  at page 2-5.

Regards,

A. Zaatari

[coolrthancoolio]

Page 2-5 is talking about the ISOLATED outputs...we have configured those pins already...I am talking about the pins on the front of the camera....for direct lighting...from there you should be able to control the current through VBAI.We could use ISO outpit but we already have one hooked up to a buzzer and another hooked up to an arduino.

The pins on the front have a continous 50-500mA....5V TTL and/or 24V Strobe...  I notice when I check the voltage of the continous 50-500mA its a constant 39V in a negative polarity...even when I increase or decrease the current it still reads a voltage of 39V.

[BlueCheese]

The direct-drive lighting output on the 1742 is a constant current source. The onboard controller varies the voltage to supply the amount of current specified. Because it is a constant current source, you should not have any current-limiting resistors inline with your LEDs because you would just be wasting power.

The link to the PDF manual someone posted above also clarifies the min/max voltage specifications of the constant current controller  (basically the voltage drop across your LEDs needs to be within 7-30V). Typical LEDs have a voltage drop of around 1.8-3.3V depending on type and color. Thus you would usually need to have several of them in series to get a voltage drop of at least 7V.

Additionally, if you are not using LEDs designed for high-intensity lighting, they might be only designed to accomodate 20mA or so, while the 1742's controller has a minimum of 50mA. Thus, you might need to put more than one of those chains of LEDs in parallel to split the current up.

Generally the lightheads designed for usage with cameras like the 1742 have their arrays of LEDs wired up in a combination of parallel and series circuits to achieve desired current and voltage characteristics.

Eric