SPYDAR Circuit Monitor
failures in electronic systems are some of most difficult to diagnose.
This device is designed to run for days at a time looking for a failure
and logging the event.
The unit is based on a PIC16F84.
Six digital data lines are brought in via a 74hc165 shift regiser.
The shift register is connected to a set of series resistors so that any
voltage from about 3 volts to about 30 volts will read as a high condition.
A single analog line is read using an ADC8031. (Note: with todays
PICs, it would be better to use one with the A/D built in).
Once activated, the unit counts off time down to 1/100 second. Any
change of state of the 6 digital lines causes it to store the time, the
state of the six lines and one analog voltage. If nothing happens
within 10 minutes, it logs it as a non-event. The reason for
this is to allow more dense storage of times in the eeprom by storing
delta times between events.
based program that reads out the data constructs an elapled time table
based on summing delta times. This is writen to a text file
- see this sample.
The circuit is designed to shut itself off either manually or when the
eeprom is full. No power is drawn in the off mode. The DOS
capture program is written for COM1 and connects to a stereo mini jack
on the unit.
Connect a 9 volt battery to the unit.
to computer serial port)
RB7 plays a medium tone burst and starts the unit running.
RB6 plays a higher tone burst and turns the unit off.
com port connected)
RB7 plays just 4 tones and enters communication mode. Run
PC software to download datat to text file.
RB6 plays 2 tones and powers off.
So far this unit has facilitated the repair of one RV-based propane refrigerator.
Provided for you use: Schematic, device
Source file, device Object
file, DOS C Source file, DOS Executable.