Electronic_SCL_Sel

Teletype Electronic

Simple Current Loop Interface with Selected Components

This design based on the circuit above but with a dedicated opto coupler the electronic can simplified. This design allows also a voltage source of 120V.

Status: tested and working

Note: The bridge rectifier can be skipped if you are sure you do not change poles!

Components

Bridge Rectifier:

• any with Vrrm>200V and I>100mA

Opto coupler Receiver:

• PC817, LTV817 (Vce=35, CTR>50%)
• any opto coupler with CTR>50%

Opto coupler Transmitter:

• TLP627 (Darlington, Vce=300V, CTR=1000%)
• PC725 (Darlington, Vce=300V, CTR=1000%, different pinout)

PCB Layout Example

The following schematics is identical but the components are replaced for a better layout on the PCB.