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AQ6 Voltage warnings and wiring advice

WARNING: The AutoQuad board is a sensitive electronic device.   Care should be taken to stay within its voltage tolerances, avoid static discharge, and maintain proper ground connections during operation.  Please heed all the peripheral specifications (serial adapters, RC devices, telemetry radios, etc) and wiring advice provided in this documentation.  Failure to do so could easily lead to critical failure of on-board components (typically the microprocessor chip), requiring replacement.
PPM Signaling Voltage Warning : Most PPM sum receivers and converters use 5V for signaling (known exceptions: FrSky and “newer” Futaba receivers). The AQ FC is a 3.3V device, with “5V tolerant” I/O ports. This means that while it should work with 5V signaling, this is NOT the recommended voltage for extended operation, according to the microprocessor manufacturer (STM). We are working on a practical solution to this issue and will publish more information. Essentially, a simple voltage divider (a couple resistors of proper value) should bring the signaling voltage down to a safer level.

Twist your wires!

It is very important to reduce inductance in power cables and its influence on low-voltage signal wiring connected to the flight controller (such as RC Rx, ESC signaling wires, telemetry or serial adapters, etc).   A current surge (like plugging in the flight battery) will induce a large voltage spike across ALL wiring (and distribution boards) between the battery and ESCs.  This voltage spike could, in turn, cause a smaller voltage spike in any other wires running physically close to the main power cabling.  This can easily destroy the low-voltage input and output ports on the AutoQuad hardware!

The easiest and most basic way to reduce inductance is to twist ALL your wires.   This means twisting each positive & negative lead around each other, as evenly and as completely as possible.  In the case of 3-wire leads, twist all 3 wires around each other, evenly (with flat cables it can be easier/better to separate the 3 wires first).  Always try to avoid loops in wiring, especially where the negative and positive wires would separate from each other (such as in a sharp bend).  The best way to keep wires twisted and running together is to bind them after twisting, with tape, lots of wire ties, or something similar.

The other very important technique is to keep your high-voltage and low-voltage wiring as physically separate as possible.  Routing wires connected to low-voltage ports on the flight controller near power lines is very likely to kill that port or even the whole microprocessor!

AQ Signaling Voltage

The AutoQuad flight controller is a 3.3V device, which is “5V tolerant” on some ports (like ports M1-14 and serial). This means that while it can a handle 5V input signal for some amount of time, this is not the recommended voltage for stable operation.  The main problem is that at 5V there is very little overhead left for a voltage spike.  A short transient spike over 7V will almost certainly ruin the port or the whole microprocessor unit.  Voltage spikes can easily occur in multicopter setups due to the high-power cabling running to the speed controllers and the close proximity of all wiring due to the limited amount of space available on a typical frame (please read our recommendations on wiring).

This page was created on 17-Sep-13 by MaxP. Last modified on 17-Oct-14 by kinderkram.