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daq board to circuit connection

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Hi,

I need to use relay with digital output of daq device, i just want to be sure,

do i need to use any resistor or anything? or can i connect directly daq card and relay?

 

thanks a lot

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Message 1 of 15
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Most likely you will need some kind of buffer or driver.  A few solid state relays may have low enough current requirements to drive them directly from a digital output.  Check the specifications of your relays and DAQ DO.

 

A driver which works well with many relays is the ULN2003 or other devices in that family.

 

Lynn

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Message 2 of 15
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@alican wrote:

Hi,

I need to use relay with digital output of daq device, i just want to be sure,

do i need to use any resistor or anything? or can i connect directly daq card and relay?

 

thanks a lot


an illustration using an ULN(500mA single output:50V) with a 12v relay (nominal operating current 8.3mA) connected to the 6009 Daq: P17DO and P32GND...

daq uln2.png

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Message 3 of 15
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Yes, you will almost certainly need a signal conditoning circuit, which mostly contains resistors and buffers (octal usually) or line drivers. This acts like an interface to protect the NI device (which would have some circuitry inside it anyway) but more importantly, so that the signals you feed in will be 'converted' into an 'acceptable' level.

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how would you have to to manipulate the circuit above to get 12V output voltage and 300mA output current?

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Message 5 of 15
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The circuit apok posted will work at 12 V and 300 mA without any changes.

 

If you need multiple loads, just wire other DO lines and loads to unused parts of the ULN2003.

 

Lynn

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What would the ouput from pin 17 of the daq be? 5 volts? Will the 12V output and 300mA output current be taken from the pin 16 of the uln2003?

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@Scall93 wrote:

What would the ouput from pin 17 of the daq be? 5 volts? Will the 12V output and 300mA output current be taken from the pin 16 of the uln2003?


The DAQ only puts out 5V and a relatively small current.  The point of the ULN2003 is to output the 12V with enough current to drive your relay.


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Message 8 of 15
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Can you take a look at this 12vdc peristaltic pump circuit. Should this work ok? Thanks

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Message 9 of 15
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  • Daq GND and 12 power GND should be connected, otherwise your voltages are floating.
  • UNL common , Pump POS and 12 power POS connected together.
  • output signal of ULN connected to Pump NEG

 

the uln is a low side driver  Smiley Wink

 

you must consider the current needed to drive the pump..does the ULN driver has enough? otherwise an SSR, FET or another high current transistor, optocoupler, etc.

 

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