Duty Cycle Converter

On AC-CDI v7.9, DC-CDI v7.9 or DC-CDI v2.1 the tacho output available at RB5/PIN11/TP1 can drive a tachometer.
The signal is a +5volts level and 5% Duty Cycle signal:

but some tachometers need a +12v level at 50% DutyCycle signal !

In order to work with such tachometers I created a small microprocessor able to convert the Duty Cycle while keeping the same frequency.

The IC or the Firmware are available in the SHOP section.

Characteristics

Min

Typ

Max

Unit
Output Duty Cycle

50

%
Input Duty Cycle

0.1

99.9

%
Input Voltage

2.5

5

V
Output Voltage

5

V
Frequency

5

800

Hz
RPM

30

48,000

RPM

Working:
The processor convert the input signal to an even 50% ratio.
A +5v level 50% DutyCycle is available at pin2, then a NPN transistor raise the signal to a +12v level.

Extend 0.1% DutyCycle at 8Hz:

at 800Hz:

or shrink a 99.9% DutyCycle signal:

Schematic:

Wiring:

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