12-27-2009 02:41 PM
1) The schematic is OK. The resistors are there where they should be.
2) Yes, you are right the output voltage of this device is 3.8V. Most (small) Mosfet switch at 2V. So it should not e a problem but check the datasheet of the mosfet for the 'Gate Threshold Voltage' (Vgs)
3) The mosfet gate current is almost 0 (< 1µA) so now problem for the DAQ. The mosfet will provide the current for the valve. The 1k resistor is just to protect the mosfet
Just ask if something is still unclear.
12-27-2009 03:20 PM
Thanks!
Will try and then update findings.
Just wanted to clarify one more issue to beter understand whats happening:
1) Can one turn on DO via labview and keep it on to keep valve open (SMC solenoid valve is NC). Will the TTL pulse from DO cause valve to close once voltage goes from high to low for the outgoingTTL pulse from DAQ DO to MOSFET switch gate?
2) How does one keep gate voltage high via DO via labview?
Thanks for clarifying. Just want to make sure I follow the operations.
12-28-2009 02:16 PM
You can turn on and off the MosFet (and Valve) with any digital output from a DAQ device. This is not a pulse but a steady '1' or '0'.
With a '1' you switch the MosFet on and with a '0' you switch it off.
For sending a boolean value to your digital output with LV see the various example's and code on this site.