Measurement Computing USB-PDISO8/40 - Manual (Page 15)

USB-PDISO8/40 User's Guide Functional Details
Daisy chaining additional modules to the USB-PDISO8/40
Daisy chained MCC USB Series products connect to the USB bus through the high-speed hub on the USB-
PDISO8/40. You can daisy chain a maximum of four Measurement Computing USB products to a single USB
2.0 port on your computer, or a maximum of two devices to a single USB 1.1 port. Use the supplied cable or an
equivalent cable for daisy chaining to additional MCC USB Series products.
To daisy-chain two or more USB-PDISO8/40 modules, follow the steps below. This procedure assumes you
already have one USB-PDISO8/40 connected to a computer and to the external power source. The USB-
PDISO8/40 already connected to the computer is referred to as the connected module. The USB-PDISO8/40
you want to daisy-chain to the connected module is referred to as the new module.
1.
2.
3.
Connect the
Power OUT
connector on the connected module to the
POWER IN
connector on the new
module.
Connect the
USB OUT
connector on the connected module to the
USB IN
connector on the new module.
For each additional module you want to add, repeat steps 1-2, with the module you just daisy chained now
being the connected module.
An example of a daisy chain system is shown in . Figure 3-2
Figure 3-2. USB-PDISO8/40 daisy-chain connections (configuration not near full power load)
Power limitations using multiple USB-PDISO8/40 devices
When daisy chaining additional Measurement Computing USB products to the USB-PDISO8/40, you must
ensure that you provide adequate power to each module that you connect. The USB-PDISO8/40 is powered
with a 9 VDC nominal, 1.0 A external power supply.
When connecting multiple modules, power supplies with higher current capability are available from MCC,
such as the CB PWR-9V3A.
Supply current
Running one USB-PDISO8/40 with all relays "on" draws 820 mA from the 1 A supply. When using the USB-
PDISO8/40 under full load conditions, you cannot daisy chain additional Measurement Computing USB
modules unless you supply external power to each module in the chain.
If you are not sure how much current your application requires, we recommend that you provide separate power
to each Measurement Computing USB product that you connect.
USB OUT to
USB IN
USB I
USB port to
N POWER OUT
POWER OUT
to POWER IN to POWER IN
USB OUT to
USB IN
CB - PWR - 9
power supply
to POWER IN
3-3