Matrix Orbital LK202-24-USB - Manual (Page 12)

LK202-24-USB rev 1 12
Figure 2-3 General Purpose Outputs
GPO 1, GPO 2, GPO 3
Maximum allowable current is 20mA, which is enforced by a 240ohm current limiting resistor. If the device
being switched has a resistance of 240 ohms or more the corresponding resistor may be shorted. Solder a
small jumper wire (wirewrap wire is good) from the feed through hole to the corresponding negative pin for
the GPO in question.
Note: The GPOs do not have any over current or over/under voltage protection so care must be taken when
using them. For instance if the external device is a relay it must be fully clamped (using a diode and
capacitor) to absorb any generated back electro-motive force (EMF).
10 - 100 uF
1N400 1
Relay
coil
GPO
+ -
Figure 2-4 Clamping a Relay