The OM1894 features patented smart triac drive at mains zero crossing for controls of loads such as heating element, fan motors, compressor cooling motor and other complex loads. The smart traic drive circuit reduces the need for snubberless triacs and costly EMI filtering.

OM1894 is suited for applications where accurate control is required from one or two NTC or PTC thermistors sensors that can be interface to external circuitry, which is important if both logic and timing functions are required.

In addition, the OM1894 can be easily combined with other logic integrated circuits to further enhance the application.

OM1894, the dual sensing triac control thermostat integrated circuit significantly reduce the number of external component count required by combining the sensing, control and triac switching circuitry into a single 16 pin package

• Dual or single sensor operation
• Sense circuits outputs available
• External triac control available
• AC powered sensor
• Independently fixed or variable
  cut-in/ cut-out thermostat

• RFI elimination smart triac drive circuit
• No DC component in AC mains
• Hysteresis can be set using external components
• Low supply current requirement
• Variable ON/OFF cycle times
• Gate pulse width may be externally set

• Accurate temperature control
• Negative triac gate drive avoids insensitive quadrant operation
• Application flexibility with dual or single sensor operation

• User can easily set the hysteresis at the temperature set point
• Low external component count
• Low electronics cost
  

The OM1894 is suited for application in refrigeration controller as a:-

• Dual sensor refrigerator thermostat
  With one sensor each in the cabinet and evaporator of the refrigerator, the internal logic in the OM1894 is such that the compressor is only allowed to start when both the cabinet and evaporator temperature meet their respective cut-in threshold

• Freezer thermostat with over temperature alarm
  The OM1894 in this application has a single control that varies both the cut-in and cut-out temperatures together with an over temperature alarm to indicate when cabinet temperature is greater than upper set trip point.

• Compressor lockout
  By combining the OM1894 as a dual sensing temperature controller, with a few additional components, additional features, such as, "Compressor Lockout" and an audible over temperature alarm can be incorporated into a Refrigeration Control Module.

Refer to Hendon Semiconductors HM199 Refrigeration Control Module datasheet for more information

Apart from refrigerative control, the OM1894 can be used for other heating control applications such as food warmers.

• Temperature Control Family

• OM1894 datasheet
• HM199 datasheet