Sequencer - Ham Radio Projects

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Sequencer is an assistive device that protects a variety of amateur equipment in common use from damage. For example LNA, used together with TCVR and PA or LNA used with TCVR, transverter and PA...etc. , all of these equipments need sequential timing for their proper activation and safety operation.

Designed sequencer uses preprogrammed ATTINY85. Sequencer should meet the requirements for correct operation of typical device assemblies. It is powered by 12V DC, has two different input ports and 4 output ports. PTT1 input port can be activated (grounded) either with foot switch or with PC. Default delay step is 20ms, see schematic for preprogrammed timing characteristic. PTT2 input is asigned for CW and its delay is set to abt. 600ms.

To prevent damage by inappropriate activation of the TCVR PTT (e.g. with microphone PTT or by activation the electronic keyer), sequencer is designed for connection to the transceiver equipped with TX INHIBIT feature. The output 4 is intended to control this feature (appropriate way). TX INHIBIT is active (transmiting is blocking) until one of input ports of the sequencer will be activated (grounded). 

The power connector P5 has pin numbers 2, 4 and 6 grounded.  Pin 3 is +12V input, pin 5 is +24V input (as an option for stronger output relay powering - it is not necessary to use it). Pin 1 (at the top) is +5V / 900mA output for eventuall external using.

As a switching MOSFETS Philips BSP89 can be used (max.300mA). In the case of relay with higher current another types of MOSFETS should be chosen (BSP149 or BSP297). 

In the case of using 24V relay, it is necesary to remove diode in 12V section at the same output port !!! Diode EGL1B is well thermally conductive, so just preheat one end and remove it out.

Sequencer can be programmed directly on the board via the programming connector J8. Meaning of each pin is apparent from the scheme and port assignements of ATTINY85. During programming SW1 must be ON.

ARDUINO UNO (with proper ATTINY library loaded and bootloader burned) was used as a programmer (board ATTINY and processor ATTINY85 selected, clock 1 MHz internal). The board was powered from Arduino (J1 unpluged!) during programming. Arduino UNO - Sequencer J8 wiring apply as follows:

                                                    J8 / 1                  -                     GND
                                                    J8 / 2                  -                      13  (SCK)
                                                    J8 / 3                  -                      12  (MISO)
                                                    J8 / 4                  -                      11  (MOSI)
                                                    J8 / 5                  -                      10  (RESET)
                                                    J8 / 6                  -                     +5V

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