Page 15
4QD series controller instructions.
Most water problems are caused by condensation or
by splashing. Water splashes must be kept away from
the electronics and we at 4QD have taken great care
to make sure this is done.
The vacuum formed cover of the controller is
waterproof and will keep off water from above. The
mouths of the controller (one each end) are sealed
with a piece of waterproof foam between board and
base (F in the above diagram of the 4QD-200)
Behind the terminals is a plastic splash plate (SP in
diagram). A notch is present in this for control wires
to pass through. For proper splash proofing this plate
should be sealed to the board using Dow Corning 734
RTV - a free flowing silicone rubber with a
consistency like treacle. Do not use ordinary si rubber
- it won't do a good job and is very messy!
To use the silicone, remove the splash plate and wire
the controller. Now, with the controller base plate
horizontal and at the bottom. run a small bead of the
silicone along the bottom (longest edge) of the splash
plate before re-fitting it. The silicone will run down
the plate and seal it to the board. Use the top cover to
hold the splash plate in place. The silicone takes
about 1/2 hour to partially set.
The controller is best mounted with the aluminium
base horizontal at the bottom so water cannot run into
the controller and collect inside the cover. Mounting
with the base vertical is permitted but there is a slight
risk of water being trapped by capillary action
between the cover and one of the boards. If trapped in
the wrong place this water could cause electrolytic
corrosion and/or failure. A drainage hole near the
mouth in the appropriate place would minimise this
risk.
Do not try to seal the base to the cover: this should be
allowed to breathe so that any condensation or water
which does enter can escape again.
In any machine you should consider whether it is
likely to be exposed to water: where will the water
come from, where will it go? Will water run along
cables into the controller or into any connector or
other sensitive point? If so you should make a small
loop so the water drips off at the low point before it
reaches the sensitive item.
If the controller is mounted on its side a drainage hole
('drain' on the diagram) in the mouth may allow water
to run out. Also you can seal the splash plate to the
side of the cover with the same silicone rubber.
Several controller have failed because water was
allowed in and was held by capillary action between
the boards and the cover in the area shown by a
pecked outlines. Water here may not cause immediate
misbehaviour - until a track corrodes through!
16 Battery Charging
Unless a trip, circuit breaker or battery switch has
been fitted, the 4QD-300 is permanently connected
to the battery. The battery charger will not normally
be capable of causing voltage spikes above the
handling capacity of the MOSFETs in the controller
which are rated at 50v (60v for -48 models).
However if the batteries were ever removed whilst
the charger is active some chargers could cause
excessive voltage spikes so this possibility must be
considered.
F
SP
drain
15 Waterproofing
