fischertechnik COMPUTING ROBO MOBILE SET 8 Mode D'emploi page 57

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Trouble Shooting
■ Experimenting is fun. That is, as long as everything is working. Most of the time this will be the case,
but unfortunately not always.
It is only when a model is not working right, that you will find out if you truly understand the mechanism
and are able to find the fault right away.
With mechanical faults at least there is something to see (assembled incorrectly) or feel (stiff to move).
But if electrical problems also arise it becomes much more difficult.
The pros use a series of different measuring instruments to troubleshoot, such as voltmeter or
oscillograph. But not everyone has such devices at hand. For this reason we want to try to zero in on a
fault with simple means and fix it.
Assembly of Cables
Before we begin with our experiments, we first have to get some of the
components from the Fischertechnik construction kit ready. The supplied
connectors, for example, are clamped to the individual cable segments.
First we cut the cables to size. We measure the specified lengths and cut the
segments accordingly. Each cable is tested after assembly using the battery pack
and the lamp. If the lamp lights up after it is connected to the battery, the cable is
ok. We will also check if the color-coding is correct, red connector red cable, green
connector green cable.
Interface Test
If a program (even a supplied one) does not work in connection with our model we start the Interface
test. This utility program enables us to test each input and output separately. Are the sensors working?
Are the motors rotating in the right direction? For all our mobile robots the motors are connected in such
a way that the wheel or the leg will move forward if the rotational direction=ccw. If everything is ok here
as well we'll start looking for a mechanical cause.
Loose Connections
Loose connections are a nasty fault. On one hand it is possible that the way the connectors fit into the
sockets is too loose. In this case you can adjust the contact springs a bit using a small screwdriver. But
be careful, if you bend them too much the contacts might break or the fit might become too tight.
Another cause of loose connections are the clamp locations where the connector is secured to the cable
with a screw. Please tighten the screws carefully! This is also an excellent opportunity to check if any
of the thin copper wires might have broken off.
Short-Circuits
On occasion you might also create a short-circuit by connecting cables incorrectly. In that case, nothing
will work as it should. The battery pack has a built-in fuse that will interrupt the current when the
temperature or the current is too high. In case of overheating the outputs terminals of the Interface will
also be shut down.
There can also be a short circuit if you fail to tighten the little screw properly that secures the electrical
connector to the cable. The screw might then stick out over the edge of the connector. If you plug two
connectors into two adjacent sockets on the Interface and their screws come into contact a short-circuit
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