Service manual

Revision D 4-14
Troubleshooting : Control PCB Theory
Series 2000 Treadmill
409110-004
Temperature Sensor
The processor monitors temperature and saves peak temperature in
EEROM data storage for use by field service. The sensor outputs
10 mV/Deg C. The op amp provides a gain of 4.92.
The 78310 A/D converter produces the following outputs
■
In hardware: A/D value = Temp(Deg C) * 10mV/DegC * GAIN *
256(max A/D counts) / VREF
■
In software: Readout Temp = (A/D value) * 4 / 10
For example:
At 25 Deg C ==>
A/D value = 25 * 0.01 * 4.92 * 256 / 5.1 = 62 (Dec)
Readout Temp = 62 * 4 / 10 = 24.8
At 100 Deg C ==>
A/D value = 100 * 0.01 * 4.92 * 256 / 5.1 = 247 (Dec)
Readout Temp = 247 * 4 / 10 = 98.8
Processor Circuitry
The 78310 runs at 12 Mhz. Its code is stored in the 8K X 8 EEROM. It can
be reprogrammed through the RS-422 serial port. The code must be
initially installed by the manufacturing test fixtures. The 78310 accesses
memory through its multiplexed address/data bus. An 8-bit address
latch (HC573) separates the address from the data. An EP330 decodes
the proper chip select from the address. The EP330 can select the SRAM,
the EEROM, or a UART (unused) at the appropriate address. It also
generates the special WRITE gate signals to write to EEROM.
The processor handles all the I/O, including one serial channel, 4 analog
inputs, and digital inputs and outputs, to control the treadmill grade
and speed.
Analog Inputs
Elevation feedback (from the pot), manual speed, and manual elevation
analog inputs are designed to take ratiometric voltages referenced to +5
VREF as inputs to the processor.
Speaker Output
One of the timer outputs is used to create sound through the AC-
coupled audio amplifier. A 2.5 V pseudo-ground is built using one-half
of the op amp. The other half is configured as an AC-coupled bandpass
amplifier referenced to the 2.5 V pseudo-ground.