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Poc-It Overview
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Poc-it is a power-on cycler and intermittent tester, providing a one step
solution for power-on cycle testing. Improve the quality of
your hardware and software products with this inexpensive and easy-to-use
tool. The following are just a few examples of systems that can benefit from
testing with Poc-it:
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| Embedded Systems |
Turn-key PC Systems |
| Circuits with Complicated Power-On Logic |
Switching Power Supplies |
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Features
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| Input Counters: |
2 high speed 5 VDC inputs |
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1 optically isolated 10-30 VDC input |
| Cycled Outputs: |
1 120 VAC @ 10 amps |
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1 5 amp relay contact |
| User Interface: |
1-Line LCD Display, 4 button key pad |
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Simple menu driven interface to: |
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-Set On and off times of each output with a 10 ms resolution |
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-Reset Input Counters |
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-Start and Stop the test |
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-View cycle counter for all three inputs and both outputs |
View the Poc-it Manual for more
detailed information about how Poc-it works.
The following options extend Poc-it's functionality:
PC Remote Control - allows Poc-it to be
controlled from a PC.
PowerCycler - adds AC phase control, making
Poc-it a powerful tool for testing power supplies and power sources.
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The Problem
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In over twenty years of developing electronic systems, we have seen a common
problem plague many systems during the development cycle. This problem usually
manifests itself intermittently and occurs following power up.
It can be caused by either hardware or software, and it is never obvious which
is the problem's source.
Frequently, such a problem is difficult to duplicate, and occasionally the fix
is questionable. Often, several attempts must be made to fix it.
After each change, the system may need to be retested for thousands of cycles
before the problem manifests itself again.
Here are just a few of the design problems that can cause intermittent operation
following power-up:
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Hardware
- Improper Hardware Initialization
- Temperature Sensitive Race Conditions
- Vibration Sensitive Interconnects
- Component Sensitive Race Conditions
- Noisy or Noise-Susceptible Power Circuitry
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Software
- Incorrect Hardware Initialization
- Unprotected Interrupt Windows
- Power-On System Test Problems
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Conventional Solutions
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Two things generally characterize our experience. First, design engineers
rarely test their equipment under repetitive power-on cycling (i.e. thousands
of cycles) as part of their design verification. Testing generally occurs only
when the problem manifests itself as a "cannot duplicate". Secondly, once the
problem occurs, the test engineer or designer jury-rigs a piece of test
equipment consisting of a pulse generator, a relay, and a couple of counters,
usually wired up at 6:00 PM.
Another common solution in the manufacturing environment is to use a
general-purpose PLC. Generally, this is expensive and complicated to set up
and to operate. Most design labs do not have access to such equipment.
Our dissatisfaction with existing methods while working on our own projects
led us to search for an easier way to perform this type of testing.
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MicroTools' Solution
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Now there is a better solution. Poc-it's power-on cycler and intermittent
testing capabilities provide an integrated solution to the problem of
power-on cycle testing.
Not only is the Poc-it simple to use, it is inexpensive enough to have several
in the lab to facilitate early testing of systems by hardware and software
engineers before the problem manifests itself.
Every microprocessor
controlled system should be subjected to this kind of testing during the design
phase. In addition, every sophisticated power supply should be tested in this
manner. Many systems should be subjected to this kind of testing during
production testing. Generally, in the past, neither design not production
testing of this type were performed. Now, Poc-it makes it easy and
cost-effective to do both. Poc-it is used here at MicroTools, where our
philosophy is, "If it's not tested, it doesn't work!"
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Case Histories
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On one job, a sophisticated avionics box was designed for a fighter aircraft.
During production temperature and power cycling, one in approximately one
hundred boxes would fail one relatively simple power on test (Power and
temperature were being cycled by a piece of sophisticated Automatic Test
Equipment). Deep in the production cycle, it was discovered that a certain part
was being used outside its acceptable design tolerances. Poc-it could have been
used early in the design cycle by the hardware designers to uncover this
problem long before production.
On another job, certain pre-production units of a PC-like embedded system were
occasionally failing to become operational following power up. When it was
failing, it would fail once every 10-20 power ups. At other times the same
system could be cycled hundreds of times with no failures. After several days
of test and analysis by a hardware and software team, a very small window in a
commercial communications library was found where interrupts should have been
disabled but were not, causing the software to crash. Software had already been
released and production PROMS burned for a large quantity of systems. Poc-it
could have been used early in the design cycle by the software designers to
uncover this problem long before the software was released.
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