Matrix Orbital VFD2041 Legacy - Manual (Page 13)

VFD2041 rev 2 13
Maximum allowable current is 20 mA, which is enforced by the 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) between the two feedthrough holes as shown in Figure 2-10.
GPO
+ -
240 ohm
resistor
Jumper
Figure 2-10 Bypassing 240 ohm resistor
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 – see Figure 2-11) to absorb any generated back electro-motive force (EMF).
10 - 100 uF
1N400 1
Relay
coil
GPO
+ -
Figure 2-11 Clamping a Relay