SGC Smartuner SG-211 User Manual download pdf (Page 41)

SG-211 User’s Manual

A diode pair is associated with each coil. The series

diode provides isolation necessary for proper operation of

the matrix. The shunt diode prevents voltage spikes on

turnoff.

Extensive capacitor bypassing is used to prevent RF from

interfering with the proper operation of the matrix.

On page two of the schematic diagram transistors Q1

through Q12 provide pulldown drive for the rows and

pullup drive for the columns of the matrix.

4.5 Microprocessor

A PIC flash microprocessor was selected for the very low

sleep mode current drain that is key to long battery life.

Inputs to the microprocessor are forward and reverse

power, and a sample of the input signal from which the

frequency is measured. The frequency measurement

makes it possible for the processor to store historical

values for a correct match over the frequency range.

Thus, when changing frequency, the previous values are

recalled, greatly speeding the matching process.

U2 provides a reference to one of the A/D inputs to

measure battery voltage. The processor flashes LED DS1

when a low battery condition is detected.

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SGC Smartuner SG-211 User Manual Page 41