The top of the sNQ Shorty looks much tidier than its big brother, here the experience gained with the first work increases. The cables between the control unit and the LEDs and the motors are now laid on the underside of the circuit board and lead through the holes to the pads provided for this purpose.
sNQ Shorty – Quadcopter of Harald Sattler
“After initial flight tests I can confirm the function of the Mega328 with 16 MHz at 3.3 V operating voltage. Of course, one must be aware that the chip is operated outside its specification and no one can guarantee that the two chips and the ?C function are compatible with all possible conditions. It may well be that the shorty in the living room at 20 ° prima flies, then one opens the door and there comes cold air into the room, the copter simply crashes.”
“With the sNQ Stretcho, we pushed the motors down as far as possible through the brackets, because this would dampen or even suppress vibrations due to the engine running, and disturbances of the IMU chip largely fall away. In the case of the sNQ Shorty, this can only be implemented to a limited extent, …”
The timer is built using four small inexpensive CMOS integrated circuits. This allows it to run on just 3V from two small AAA batteries. U1 is a 74HC688 8-bit equality comparator. It compares the switch settings to the counter output and will set pin U1-19 low when they match. The actual counter is U2. It is a 74HC4060 14-stage binary ripple counter with built-in oscillator.
The G-switch itself uses a cantilevered metal bar that pivots down as the rocket accelerates upward. The metal bar actuates a small micro-switch that triggers a digital counter to begin the timing sequence. The timer is designed so that it will not start unless the micro-switch has been activated for a duration of at least 0.5 seconds.
G-switch timer – Vern Knowles – The timer was built using a small prototyping circuit board and point-to-point wiring.
U3 is a 74HC74 D-type flip-flop that is used as part of the triggering logic. U3-12 will be low when the counter matches the switch settings. Consequently, on the next oscillator clock edge from U2-9 the flip-flop output at U3-9 will go low. This is the event that activates the 2N4403 transistor that fires the flash bulb.