Optoisolator


Posted on May 4, 2012

The circuit protects a solid-state relay from overloads. The circuit limits current, automatically disconnects the load after


Optoisolator
Click here to download the full size of the above Circuit.

detecting a short circuit, and develops a fault-condition output signal. In normal operation, the controlling sets the flip-flop, IC1, which turns on transistor Ql. When Ql turns on, current flows through the solid-state relay"s input, thus activating the relay. If an overcurrent or fault condition occurs, the excessive load current flowing through the relay develops enough potential across sense resistor R5 to turn on one of the optoisolators, IC4A or IC4B. The optoisolator"s output transistor diverts current around the solid-state relay"s input, which limits the current that the relay"s output can pass. If the overload is severe enough, the optoisolator pulls the input of the Schmitt trigger above its threshold, thus clearing the flip-flop and turning off the solid-state relay. R2 has two functions: It keeps the input of the Schmitt trigger below 5 V max. to prevent latchup, and it forms an RC filter in conjunction with CI. The RC filter prevents spurious triggering of the Schmitt trigger. You can use the output of the flip-flop to signal overload conditions to the controlling uP.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Speed Controler for R/C Models
Car Large capacitor charge controllers
Proximity alarm
Designing A Li Ion Battery Charger with Load Sharing MCP73837
cap humidity sensor circuit
Search Light Signal
project morpheus
ypbpr to rgb video converter circuit
UltraSonic Radars
LM1881 LM1881 Video Sync Separator
Peak Detector Circuit
CD4013 circuit
Refrigerator power protection circuit
lm358 alkaline battery charger circuit
Wire color music lantern controller



Top