MPOD Interlock(MPODI) Board Test

MPODI board schematic

The function of MPOD Interlock board is turning MPOD off when 2 chillers stop working to avoid possible damage due to high temperature. When at least one chiller is working well, all channels of MPOD can be switched on remotely by software. When 2 chillers stop working, all channels of MPOD will be switched off with their specific down ramp
Here is schematic of 1st version MPODI board.MPODI_schematic_v1.pdf The second version of MPODI board will be produced soon.

MPODI board connectors and pin assignment

MPODI connects to MPOD Interlock connector via DB9 connectors. There are 3 MPOD connected to MPODI board at the same time. The spare DB9 connector is backup. MPODI connects to Chiller PLC via LEMO connector. TIM board provide 6V power supply to MPODI board. There is a LEMO connector for monitoring. MPOD and MPODI board connect via DB9 connectors. Here is the pinout of J2, J4, J6, J7.

PIN number	Function
pin1	Control signal from MPODI (5V/0V)
pin5	GND
pin9	TTL high from MPOD (5V)

MPODI board sends TTL high signal to Chiller PLC board, then Chiller PLC board sends chiller working states signal to MPODI board. When the chiller is working well, chiller PLC board sends TTL high signal to MPODI board. When 2 chillers stop working, chiller PLC sends 0V signal to MPODI board. Here is the pinout of J3
If we have no chiller PLC, for now, we could fake chiller states signal.

PIN number	Function
pin1	TTL high signal from MPODI (5V)
pin2	Chiller states signal (0V/5V)

TIM board sends power to MPODI board. Since the current from MPOD DB9 is not enough, we have to connect TIM to MPODI to provide current. Here is the pinout of J1.

PIN number	Function
pin1	+6V from TIM board
pin2	0V

We could monitor chiller states via LEMO connector J5. Here is the pinout of J5.

PIN number	Function
pin1	Chiller states signal (5V/0V)
pin2	GND

MPOD Interlock board test

1. We use TIM v4 power supply cable and TIM splitter cable for MPODI basic function test. Since we don’t have chiller PLC, for now, we will fake signal from chiller PLC. According to the MPOD manual, the pin9 output current is 25mV. Because running MPODI board need around 100mV, we use TIM board to provide 5V power to MPODI board.
Connect cables according to picture1 and test voltage between pin1& pin2 on J5. When chillers stop working, chiller states signal should be 0V. 2. Then we fake a “chillers work well” signal. Connect cables according to picture 2. Connect pin1 and pin2 of J3 using TIM PS cable, and measure the voltage between pin1 and pin2 of J5. Chiller states signal should be 5V.

-- DiWang - 2020-06-27