Digital I/O
Not getting 5V on Digital Out lines for 6210
I am trying to control a couple of low power relays. Their data sheet states that to switch the relays, a potential of 5VDC and 21mA is required. I looked at the 621X user guide for the 6210 and saw that the DAQ can put out a maximum of 50mA at 5V. Thought this was my perfect solution to the issue I had.
I install the 2 relays and connect the switching coils to the PFI4 / PFI5 lines and the other side to Digital Ground. When I go to control the relays, the potential between the PFI line and Digital ground is only 3.8V and I checked the current... it was only 15mA while "switched".
I thought that I might have missed an I/O on the DAQ that might be using power, I grabbed another 6210 and tried outputting the same +5 volt signal to the relay using MAX with no other connections made. Same problem, I only see 3.8 V going to the relay.
Is there an explanation why I can't get to the 5V that I need? I'm confused why I'm seeing a voltage drop when I'm not even maxing out the supposed current supply capabilities of the 6210.
Thanks for any help in advance. 
Each output can only output 16mA. If all of the DIO were on, then in total the output current will max out at 50mA. So the device is acting just as specified.
| Current Drive Single | 16 mA |
| Current Drive All | 50 mA |
After some looking around, you might want to consider the USB-6509. It claims 24mA per channel for up to 1.5A.
Or there's the USB-6525 which has 8 solid-state relays that can handle up to 500mA each. You would have to supply your own 5V though.
