Relay and DAQ for switching a DC Motor

[RavensFan]

You can use a contactor for a DC motor.

Look at something like this.  SC-E04G-24VDC

But I still recommend talking to an electrical engineer familar with this stuff.

[aputman]

Most DAQ cards are only capable of supplying a few mA of current.  in your case, the USB-6008 can supply 5mA.  This is not enough current on it's own to power a coil on a relay of the size you need.  There are some exceptions but you will pay good money for them.  There are relay driver circuits that you can buy online that run off of TTL logic but they have to be plugged into another power source (wall plug, etc) in order to have enough power to flip the relays.

[svans5]

We have operated the relay through DAQ card to light an LED and it's working fine. We've purchased a contactor mx 12dc LnT contactor with control coil voltage of 110V DC. I'm sending the picture here. We did not get a connection diagram,. How do we connect it with the relay, supply and motor? (in terms of terminals)

[svans5]

We have connected the contactor in series with relay, supply and dc motor, but when we energise the relay through a 5V cell and the DC supply is also given, the motor (or any other load) does not turn on. We have connected the supply line to L1 and the load is connected to terminal T1

[aputman]

The picture you posted appears to be a block for an ice cube relay.  On it's own, this block does nothing.  You should be able to buy relays that plug into this block.  The reason you didn't get a connection diagram is because that information is dependent on the relay that is plugged into the block.  Take Raven's advice and seek help from a professional. 

[RavensFan]

Here is their catalog.  http://www.larsentoubro.com/lntcorporate/uploads/product/Mini%20Contactors%20Type%20MX%20.pdf  Though it is very unclear.  They have a Power Contactor section on page 3 that has the MX12 DC, but it doesn't talk about a coil.  There is a contactor relay on page 4 that does talk about different coil options.  I suggest you contact that company, get some better technical data and instructions from the.

There is no way you can use 5VDC to power a coil designed for 110 VDC.

You should get a 24VDC power supply and a contactor with a 24VDC coil.  Use a smaller relay( or some relay driver circuit) that will turn the 24VDC to the big contactor coil on and off.

[svans5]

The connection diagram we're using is attached here. The relay is working fine in this circuit. Can a DAQ card be used in place of the 9V supply across the relay?

[RavensFan]

I'm glad you got it working as far as you did.  But I'll tell you, I'm not impressed with this company's products.  It seems very awkward that they are saying to use the high voltage circuit that is also powering the motor to drive the coil that enables/disables the motor.  Thus forcing you to use their secondary relay to turn on and off the main contactor coil.  Any good company would have all of that in a single body so that you can actually have a lower voltage of 24VDC turn on and off the main power supply.  (By the way, I'd recommend getting the add-on thermal circuit breaker.)

You won't be able to use a DAQ card to supply 9VDC to this coil unless it as the voltage and current capability.  Their catalog says it needs 2.8 W.  That is about 1/3A @ 9V.  The USB-6008 is only capable of a few milliamps at 5 V.

You still need to get a relay driver circuit.

[Henrik_Volkers]

Well, I usually like to use Hockey-Pucks  5V 8.4mA input, BUT

YOU NEED TO KNOW WHAT YOU DO!!    >100V DC  isn't nice to touch 😉 And don't miss the free running diode or snubber!

A Relay can open ALL connections to the punp.   Water and current !!