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HESC Series FAQ

1. In numerous manuals, an HESC is referenced, but the Tri-M site doesn’t list an HESC product.
2. How can a Windows NT based operation system (including Windows 2000 & Windows XP) turn off the HESC104 outputs to implement UPS control function?
3. Is it possible to communicate with the HESC power supply if the counters have been incorrectly altered and the power supply does not turn on?
4. Does the HESC support charging of Lithium Ion batteries?
5. Can the HESC be used in a vacuum environment?
6. What is the purpose of the SD input on the HESC?
7. How long can the BAT104-NiMh battery backup power the HESC?
8. Can the HESC monitor the charge level of the battery backup?
9. How do I configure the HESC using the SCU.exe (Smart Charger Utility) to measure the temperature over the I2C/SMBus as opposed to measuring it using the thermistor?

Q. In numerous manuals, an HESC is referenced, but the Tri-M Engineering WEB site doesn’t list an HESC product.

A. The term HESC refers to any of the HESC products.  When reference to a specific model is required, the specific model name (HESC-SER, HESC-SERD or HESC104) is used. From the command function point of view, there are few differences between the HESC-SER, HESC-SERD and the HESC104 even though they have different Host interfaces (the SMBus is usually thought of as a battery interface, but it may also interface with a Host CPU or a microcontroller)

Q. How can a Windows NT based operation system (including Windows 2000 & Window XP) turn off the HESC104 outputs to implement UPS control function?

A. The HESC104 can be commanded off via a hardware interface, or through a software command as follows.

1. Software Interface:

• The Host CPU can issue the HESC-UPS firmware command ShutDown(0x97) over the PC/104 bus instructing the HESC104 outputs to be turned off after a delay of 1 to 65535 seconds. The Host CPU issues the ShutDown(0x97) command with a delay long enough to allow the Host CPU to finish shutting down the file system and application programs before the HESC104 outputs are turned off.
• Note: The EEprom Cmd98SDDef(0xE6) register must be set to a non-zero value for the ShutDown(0x97) command to be enabled.  Also, the value in the Cmd98SDDef(0xE6) register limits the length of the shutdown delay that can be used with the ShutDown(0x97) command

2. Hardware Interface:

• The built-in UPS functions of the Windows NT, 2000, & XP operating systems can directly control the HESC104 as a UPS by interfacing the following serial port control signals to the HESC104, BL, PF & SD signals:
• BL (Battery Low) on HESC104 to DCD (pin 1 of DB9) on Host CPU.  Requires buffering from TTL level to RS232 level.

• PF (Power Fail) on HESC104 to CTC (pin8 of DB9) on Host CPU.  Requires buffering from TTL level to RS232 level.
• RTC (pin 4 of DB8) on Host CPU to SD (Shutdown) on HESC104.  Requires buffering from RS232 to TTL level.
• Tri-M Engineering also manufactures the HESC-SER DC to DC converter.  This unit has the same dimensions and provides very similar performance, but has an RS232 serial port instead of the PC/104 bus.  The handshake lines for controlling the HESC-SER are already buffered and the UPS control of Windows 2000 can be used directly.  Note:  The HESC-SER supports the same software commands as the HESC104 and a full software UPS interface could be programmed.

Q. Is it possible to communicate with the HESC power supply if the counters have been incorrectly altered and the power supply does not turn on?

A: If for some reason, (like an incorrect profile setting) the main outputs don't come on, wiring +5V into the HESC +5V outputs will enable communication with the HESC again (Main input power still needs to be applied as usual).

The profile settings can then be "fixed" and saved and when the HESC is re-powered, the changes will take effect.
Note: The procedure for uploading the firmware and profile is listed at the back of the HESC-UPS firmware manual.

Q. Does the HESC support charging of Lithium Ion batteries?

A. The HESC can charge Lithium Ion batteries if:
1. They have an internal safety circuit.
2. Or, they are an SMBus battery pack.

Q. Can the HESC be used in a vacuum environment?

A: None of the Tri-M products are "certified" for space, however they are frequently used in that environment. A special version of the HESC (removal of the one and only electrolytic capacitor) allows the HESC to be used in ultra low-pressure environments such as space. Removal of this one capacitor increases the minimum input voltage to 12 volts but the maximum 40 volts is still valid.

Q. What is the purpose of the SD input on the HESC?

A. The SD input is used by an external maintained contact switch (such as an ignition switch) to signal the HESC to initiate a shutdown or startup of the HESC104 main outputs (not including the battery charger).

Q. How long can the BAT104-NiMh battery backup power the HESC?

A. An example of the calculation required follows:

The BAT104-NiMh, when fully charged, can provide up to 22.68 Watt-Hr (2.7Ahr x 8.4V) of power backup. The system draws 1.5A @ 28 volts (not including battery charging) and therefore is a load of 42 watts. A 20 percent derating is required because of the 2.5C current draw from the battery. From this it can be derived that the BAT104-NiMh could sustain the system for a total of:

0.8 *((22.68 Watt-Hr)/(42 Watts)) = 0.432Hr = 25.92 minutes.

Q. Can the HESC monitor the charge level of the battery backup?

A. The battery charge level information is available through the through the PC/104 bus (HESC104), RS232 serial port (HESC-SER), and or the SMBus/I2C bus (HESC104 and HESC-SER) through the HESC-UPS firmware command "BattRemCapCmd(0x0F)”. The HESC104 does not have an analog output pin to indicate the battery level.

Q. How do I configure the HESC using the SCU.exe (Smart Charger Utility) to measure the temperature over the I2C/SMBus as opposed to measuring it using the thermistor?

A. The EEprom ChTempSelect(0x90) register defines which temperature sensor to use. If this register is set to zero, the thermistor will be used, otherwise a digital sensor is used. In addition, the address and command of the digital sensor must be correctly set. Please refer to section Section 7: EEprom Setpoints and Configuration Variables of the HESC-UPS manual.