Description:
This is one of the more
"Unique" designs that I have had the pleasure of doing. The
client needed to keep an outdoor electronics enclosure from
freezing during those long, cold winter nights in Fargo, ND.
Originally silicone based heaters were to be used but the
unregulated input power supply of 18-56 VDC would have meant
that the heating rate would change by 100:1 from low line to
high line input. Clearly this would not work so this simple
board was designed instead. The design uses a unique
constant current driven resistor heating string to keep the
heating rate changes to a more manageable 3:1 over the input
voltage range. An analog PID control loop adds heat as
needed to keep a remote, enclosure mounted temperature
sensor at or above 0 Deg C.
- Up to 60 watts of peak
heating power available.
- 18 to 56 VDC Telecom
input voltage range.
- PID analog control
loop.
- Unique constant current,
resistive heating element design.
- Secondary, fail safe
over temperature protection circuit.
- Four layer (all copper
planes) PCB design for maximum heat transfer.
- Environmentally rugged
design, -40 to 70 Deg C operating range.
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