June
2005, Issue 179
Precision
Frequency Meter
Cypress
PSoC High Integration Challenge 2004 Contest Winner
CONSTRUCTION
I
built my frequency meter around a PSoC Invention Board
(see Photo 3). I hand-wired the electronics on a piece
of prototype PCB. It isn’t the most elegant-looking
piece of hardware, but it’s simple and it works!
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(Click
here to enlarge)
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Photo
3—Most of the frequency meter’s components are on
the PCB, including the PSoC Invention Board and
the regulators with heatsinks. The oven box with
its heater resistors is mounted in polystyrene for
insulation. I used header pin strips and sockets
for the PCB connections. |
To
make the meter look nice, I mounted the PCB in the lid
of a plastic instrument case. The crystal oven is insulated
in polystyrene. I mounted the LCD, buttons, and input
connections on the front panel. The power and RS-232
connectors are on the back. I placed a laminated paper
overlay on the front to make it more professional-looking.
The
crystal oven was made from a small metal die-cast box.
I mounted power resistors on the sides. A small PCB
carrying the temperature sensor is mounted to the base
of the case. The internal temperature sensor, oscillator,
oscillator regulator, and output buffers are mounted
on a small PCB that’s secured to the case lid on standoffs.
This places the PCB in the middle of the case without
a tight thermal connection to the case. It helps smooth
out the ripples in the case’s temperature. The radio
is modified with a cable for 0 V, power (3 V), and audio
output, which then plugs directly into the PCB.
