How do I operate DC 5v coil relay using USB 6008?

[555buddy]

I am operating 5v relay using LabVIEW and USB 6008 as DAQ.

The maximum o/p voltage of DAQ is 5v. Relay requires +3.4v and -3.4v across the coil (min).

Since generating negative voltage using DAQ is not possible. How do I trigger the relay using some simple switch on front panel ?

[apok]

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@555buddy wrote:

I am operating 5v relay using LabVIEW and USB 6008 as DAQ.

The maximum o/p voltage of DAQ is 5v. Relay requires +3.4v and -3.4v across the coil (min).

Since generating negative voltage using DAQ is not possible. How do I trigger the relay using some simple switch on front panel ?

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you need to give more specifics on the relay....like operating current needed?  Also, know your Daq operational specifications like sourcing currents and voltages....

this question has been asked and answered many times on the forum...have you done a search?

[555buddy]

Ok..I will do a brief search again..as well as will go through all the specifications.

If still i dont get the answer, I will come back on the forum..Thanks

[RTSLVU]

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@555buddy wrote:

I am operating 5v relay using LabVIEW and USB 6008 as DAQ.

The maximum o/p voltage of DAQ is 5v. Relay requires +3.4v and -3.4v across the coil (min).

Since generating negative voltage using DAQ is not possible. How do I trigger the relay using some simple switch on front panel ?

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I think you are misunderstanding your relay.

It probably does not need both +3.4 and -3.4 VDC (that would be 6.8VDC across the coil rated for 5VDC max).

The 3.4 VDC is probably the minimum voltage it will operate at, and since it's just a coil it will operate with a positive or negative voltage in respect to ground.

The 6008 DIO could drive the relay directly as long as the relay coil current is within the current rating of the DIO. But this is not usually recommended as you could damage the DIO by prolonged over current or by the back EMF spike relay coils create with they are de-energized.

I would suggest using a driver on the DIO, it can be as simle as a single MOSFET or an open collector IC.

I have attached a drawing that should help. This was to show another person three basic methods to drive an LED from a 24V rail with a DIO port. The same thing applies to you, just replace the LED and resistor with your relay coil.

Dont forget to place a fast diode like a BAT85 or 1N4148 across the relay coil to supress back EMF.

[SnowMule · Accepted solution]

Or use an IC made for driving relays, like a ULN2003...

one leg of the relay to +5V, the other leg to the output of the 2003.  Ground the 2003, and hook the DAQ's DO lines to the appropriate input on the 2003.  Drive the digital output low to turn the relay on.

[555buddy]

Thank you...ULN  2003 as relay driver is working perfectly. I have connected diode IN4004 across the coil for protecting the DAQ. 

Is there anything else required to prtoect my DAQ from back emf damage?

[johnsold]

The ULN2003 has a diode internally connected to the common pin (9). Connect that to your coil power supply and you should not even need the 1N4001.

The ULN200x devices are designed for exactly that kind of application. Nothing else is required.

Lynn