Tach-Rotor Adapter PLUS


The Tach-Rotor Adapter PLUS (TRA PLUS) works with 3-wire 12VDC fans commonly found in computers, computer power supplies, uninterpretable power supplies, DVRs, servers, and other electrical equipment with active cooling systems. The TRA PLUS improves upon the original TRA by adding sound and programmability. The TRA PLUS uses the same microcontroller unit (MCU) used in the original TRA thus leverages previous hardware and software design, development, and testing ensuring a stable, reliable design. The original RPM color schemes and form factor are the same as the TRA and the TRA PLUS fits in the same case. In addition to more DIP switch settings, the user can now program additional parameters to customize the TRA PLUS to their system. The addition of sound enhances visual alerts while providing a convenient feedback mechanism during operation and for quick and easy programming. User programming remains stored even if power is removed and defaults can be restored. The TRA PLUS smartly beeps during power-up (assuming all beeps have not been turned off) indicating whether default or user custom parameters were loaded. The TRA PLUS provides the following 3 functions:

1. Speed Sensing, Display, and Sound
2. Fault Indication
3. Rotor-Locked Conversion

Speed Sensing, Display, and Sound:
In the same way a computer calculates fan speed; the MCU in the TRA PLUS calculates fan speed and illuminates an RGB (red-green-blue) LED to a color indicating which one of four RPM ranges, or bands, the fan is operating. User fan speed can be verified against the DEFAULT RPM Band Colors and Ranges or the TRA PLUS can be programmed by the user to allow all four colors to span the range of speeds using the fan controller. DEFAULT RPM Ranges can be restored at any time. Using a combination of filtering and hysteresis, regions between bands were created to suppress LED flicker caused by a fan slowly crossing a band threshold, noise on the voltage/ground signals, or some other disturbance. The RGB LED can be switched ON or OFF and LED brightness can be set to High or Medium using DIP switches. The TRA PLUS has three sound modes; 1) Normal, 2) Beep Only When Programming, and 3) Disable All Beeps. Each mode is permanently stored once programmed and can be re-programmed up to a million times. The TRA PLUS ships in Normal Sound mode (sound ON for operation and programming). LED colors are based on the fan’s speed and are independent of Output Signal Type selection, e.g. the TRA PLUS will still display color bands representing fan speed even if the TRA PLUS output is set to the 2-state Rotor-Locked waveform.

Fault Indication:
When the fan falls below 30 RPM the LED becomes RED and a 1-second beep occurs every 60 seconds until the fault condition is removed. Sound can be turned ON or OFF using DIP switches. Fan FAIL overrides LED ON/OFF setting. When the FAIL condition is removed, the TRA PLUS emits 3 short beeps if it has been CUSTOM programmed. If the TRA PLUS is using DEFAULT RPM Band Ranges, the TRA PLUS emits 2 sets of 2 short beeps.

Rotor-Locked Conversion:
The TRA PLUS output can be set to follow the input from the fan’s sense wire (known as a tachometer signal - most computers use this type) or can be converted to a 2-state rotor-locked signal where the signal is LOW when the fan is spinning or HIGH (open collector) when the fan is below the FAIL threshold (30 RPM). Fan output selection is made using DIP switches.