Control Resources, Inc., Custom Examples

CRI Catalog and Design Guide Section

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Examples of Custom SmartFan Designs

Benefits of using SmartFan include acoustical noise reduction, environmental (humidity, temperature or pressure) regulation, greater product reliability, increased fan life, improved safety and energy savings. Applications that demonstrate these benefits are described below.

High-End Server Impeller Controller
4 Unit Fan Tray Controller for Large Telecom Switch
Industrial Computer Fan Controller
10 Fan Controller for Telecom Switch
Burn-in Cabinet Temperature Control System


	A high end server cooled by two backward curved impellers. The challenge of this application was to maintain very stringent current limits while providing adequate airflow to cool the server. A control board was designed that included active current limiting. Current limits were specified for normal operation, start up, hot plug and fault conditions. The fans are constantly monitored and individually adjusted. Under critical conditions, a fan could be shut down by the board circuitry. The board also provides PWM control signals to maintain predetermined individual blower speeds ą 100 RPM. Tach pulses from each fan are monitored. LED and logic status outputs are provided. FEATURES Supply Voltage: 24 VDC Logic Supply Voltage: 5 VDC Fans: Two 24 VDC, 93 watt impellers Speed Control: Individual PWM speed control for each impeller Fan Performance Monitoring: Based on monitoring current draw and tach pulses from the impellers Alarm Outputs: LED and open collector logic Active Current Limiting: Limits are maintained for normal operation, startup, hotplug and fault conditions


	A large telecom system cooled by four different fan trays. The customer requested a single board that would work with any of the four trays. A micro-controller based product was designed that would adapt its operating parameters to any of the four fan trays based on an input signal from the system backplane. The board monitors tach pulses from the fans and provides LED and TTL status signals. The board was later revised after the customer had problems with a UL flammability test. The fans caused the flames to burn longer than UL allowed. The board was redesigned to incorporate a crowbar circuit that provides LED and TTL alarm signals and/or permanently disables power delivered to the fans based on inputs from two heat detection sensors. FEATURES Supply Voltage: 24 VDC Fans: Up to six 15 watt fans Fan Monitoring: Based on monitoring tach pulses from the fans Alarm Outputs: LED and TTL Fusing: Individual fan outputs Test Input: Accepts a TTL/LVTTL logic input that causes all alarm outputs to go to the failed state to verify the control interface


	An industrial computer cooled by five fans. In addition to fan performance monitoring, the customer requested that the board also serve as a system voltage and temperature monitor. Five DC voltages are monitored. Jumpers allow 5 or 10% acceptable range selection. In addition the board monitors the system AC power source through a TTL logic signal supplied to the board from the AC source. Temperature is sensed through a remote P8 sensor. A jumper allows four maximum temperature selections. Fan, voltage and temperature status is reported through an RS-232 port and 8 bicolored LEDs. when any red LED is powered, audible and relay outputs are also provided. FEATURES Supply Voltage: 12 VDC Fans: Five 12 VDC, 7 watt fans Fan Performance Monitoring: Based on monitoring current draw System Voltage Monitoring: Five DC and one AC voltage Temperature Monitoring: Maximum temperature as selected by jumper Alarm Outputs: RS-232, bi-colored LEDs, speaker, relay

	A telecom switch cooled by ten fans. This application required providing multiple functions and 50 Watts of output power on a very small board. The board accepts and diode ORs dual power feeds with a supply voltage range of 37 to 60 VDC. The supply voltage is clamped at 54 VDC to prevent over voltage to the fans and a boost circuit provides voltages greater than the supply voltage to be applied to the fans when the supply voltage drops below 48 VDC. An I2C bus transmits circuit board inventory and temperature information from a digital thermometer. The fans are turned off when the temperature is below 0°C. FEATURES Supply Voltage: -37 to -60 VDC Fans: Ten 48 VDC, 4.8 watt fans Fan Speed Control: 48 VDC for normal operation, 54 VDC in an alarm condition The fans are turned off when the temperature is below 0°C Fan Performance Monitoring: Based on monitoring Tach Pulses from the fans Temperature Monitoring: On board digital thermometer Alarm Outputs: Optically isolated logic outputs for single and multiple fan failure Serial Interface: I2C bus transmits circuit board inventory and temperature information Fusing: Both power feed and individual fans EMI Suppression: All input and output lines Current Limiting: In-rush current at start up and output power to fans

Base Tray Heater Tray Blower Tray	Burn-in Cabinet Temperature Control System. The customer requested assistance designing cabinets for production burn-in of several types of circuit cards with varying power dissipation levels. The cabinets were desired as an alternative to expensive dedicated burn-in rooms. In addition, the cabinets would be portable. The designed system consists of two trays. The Base Tray contains six 118 CFM DC fans controlled by a SmartFan Omni SD controller (cat. pg. 32), four 220 VAC, 500 Watt axial heaters controlled by a SmartFan AC-VX controller (cat. pg. 24), one SmartFan HotSpot-Z temperature alarm (cat. pg. 50), a power supply and a relay. The Heater Tray contains four 220 VAC, 500 Watt axial heaters controlled by a relay and one SmartFan HotSpot-Z temperature alarm. The system also includes three temperature sensors and cabling to connect the two trays. The system controls the internal temperature of the cabinet (ą 2°C). Temperature is monitored at three locations and controlled at two locations. Temperature is maintained by linear/proportional control of both heating and cooling elements. The system is designed to add sufficient heat to ensure fast heating to control temperature under light load conditions. Alternatively, the system will power auxiliary air movers to dissipate excessive heat under heavy load conditions. A second system was designed to handle circuit cards with higher power dissipation levels. The system required more cooling and less heating capacity, so the Heater Tray was replaced with a Blower Tray. The Blower Tray consists of three 365 CFM AC fans and a relay mounted on a steel panel. The Blower Tray accepts a signal from the Base Tray that turns the three fans on and off based on temperature. In addition, for safety reasons, an interlock harness was designed to dissable the heaters when the front or rear doors of the cabinet are opened.

FEATURES