TCR-102 TTL Relay details

TTL Relay signal input

The relays are controlled by input 3 and 4. These inputs are TTL compatible.

The following voltage levels apply:

  • Input Low: 0 - 1.0 V = Relay connected COM-NC (LED off)
  • Input High: 1.8 V - 15V = Relay connected COM-NO (LED on)

The signal input accept voltage up to maximum 15V, meaning the relay can be controlled by other type of signal sources as well.


LED indicators

The TCR-102 has 3 LEDs indicating power status and operating status.

The green LED indicates power is connected and on.

The yellow LEDs indicate relay operation. LED on indicates TTL input signal is high and relay is switched to COM-NO.

TCR-102 inside details


Low power consumption

The TCR-102-series TTL relay are designed for low power consumption.


To minimize the power consumption, the LEDs can be disabled. This is done by removing the jumper switches (as seen in the picture above). The power on LED and relay LEDs can be disabled individually. By removing the left jumper switch the power on LED is disabled. By removing the right jumper, the two relay LEDs are disabled.


When the LEDs are disabled, the module consumes less then 20uA when relays are not operated (assumed room temperature.)


Each LED consume 20mA when turned on. The relays itself consume each 400mW. (Current depends on the voltage version, calculated by current = watt / voltage). The LED jumper switches make the module current consumption flexible to fit the available power.


Input protection for professional usage

The internal electronics are protected for common electrostatic discharge by TVS diodes at all signal and power input. A TVS Diode is a clamping device that limits harmful voltage spikes. (The TVS are located on the bottom side of the board.)

No TVS diodes are mounted on the relay connectors, as these lines are physically isolated from the sensitive electronics.


TCR-102 are ordered here