Hardware for Control of Pharmacia MV7 Motor valve

[MysAnanth]

I have USB NI 6216 and NI 9472 boards for DO.

For Motor Valve MV-7 there are two control signals - Direction and Start/Stop.

I guess - Direction takes 0 or 24 V

Start /Stop takes again 0 or 24V

Pl see attachments

Each DO channel in NI 9472 can support 750 mA

But on Start /Stop signal when connected to Digital output, motor  does not respond. When I manually gnd pin 6 Motor rotates.

I want to control the valve using LabVIEW. Do I need any additional relays?

Please let me know

[MysAnanth]

Hi All,

Anyone can help?

Thanks and Regards,

Kumar

[Buechsenschuetz]

The manual you supplied says that the direction input needs a sink current of 30mA min. to work. Most interface boards can handle up to 48mA (but some 24mA only, check the manual!) so this should not be a problem. - On the other hand, the start/stop input needs 1A sink current, and normal interface boards cannot handle this. You need a relay interface - but not just any since small relays can handle only a few hundred mA. Of course you can use a relay output for the direction terminal, too. I do not know your setup in detail but I think you should better look for a relay board which can handle at least 1A.

[MysAnanth]

Thanks Buechsenschutz.

I have a small doubt. The manual which I can enclosed is the only information I have on MV7. Does the valve for direction and Start/Stop take any TTL signal at all. Seems like it takes only 24 V signals, then in that case I need a relay output sourcing the required current. Am I missing anything here?

Assuming it takes TTL signals I can tie couple of outputs of 9472 (each can source 750 mA, It uses an external 24V Power supply and a DO switch in series)

Thanks and Regards,

Kumar

[Buechsenschuetz · Accepted solution]

Sorry, I should have been more precise. What you need is a driver board with either "open collector" or relay outputs. It is clear that your device does not work with TTL levels (maximum of +5V), however most boards with TTL outputs can be operated in "current sink mode" (i.e. similar to "open collector output" but usually the maximum voltage is 5VDC.

I am not familiar with the 9472 board but you should make sure that you can connect the outputs in parallel. The problem is that usually the output with the lowest output impedance (there are tolerances) will source most of the output current, or, in other words, there will probably no even distribution of current among the outputs. Also, it is NOT necessary to supply any current to the inputs of your device, the inputs have to be shorted to GND.

Again, I would strongly suggest to use a relay interface board. This will a) separate the +24VDC voltage from the +5VDC circuitry (burn out protection), b) can handle much more current than any electronic circuitry. Make sure to select a relay board of which the relay contacts can handle at least 1 Amp.