Technical data

66
readboard Circuits
ost electronics students gain hands-on experience with circuits by building them in temporary form on
olderless breadboards. These boards are very convenient for lab use, as they allow students to
uickly assemble and re-configure circuits using a wide variety of components.
here is much more to learning electronics th uilding circuits, though. A vital element of
lectronics education is learning how to diagnose faulty circuits through the use of test equipment.
nfortunately, the same solderless breadboards that work so well for rapid circuit construction are
rather poor for simulating circuit faults. It is very easy to see a component leg lifted to simulate an
open, or a jumper w onent to simulate a short. In o
exercises to be valid, st the circuit ut by using test
equipment.
The concept of these exercises works on the principle of ta oints on
a circuit board. Production circuit boards are commonly equipped with metal "test points" used for the
conne especially valuable when the boards are coated
with a direc s. In
cases like this, test po which circuit signals may be measured.
In the f to
with the bread nts located some distance a it. This may be done
by using a “testing jig” constructed of a long cable containing several wires and a terminal block.
tely
ken
B
M
s
q
T an merely b
e
U
ire across a comp
udents should not be able to inspect
rder for the troubleshooting
s in any way b
king measurements between test p
ction of test equipment. These test points are
protective barrier, since the coating prevents
ints are the only contact points through
t connection to the component terminal
ollowing exercises, student access is limited their faulted breadboard circuits in the same way,
way fromboard hidden and the test poi
Each student is to construct the circuit specified for each exercise, making sure the circuit is comple
functional. The “testing jig” must then be inserted into the circuit in order for measurements to be ta
at the terminal strip. It is important that the correct colored wires be inserted for their corresponding
test points.
Once the circuit is constructed and fully functional with the testing jig in place, have a lab partner or
instructor create a fault somewhere in the circuit. This is easily accomplished by lifting a leg or
removing a component to simulate an open, or inserting a jumper wire across a component to simulate
a short. Once the fault is in place, cover the circuit with something such as a piece of paper so the
circuit cannot be visually inspected.
Figure T-12
R
1
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2
1
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5
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DC
TP1
TP2
TP3
TP4
TP5
TP6
TP7
TP5
TP1 TP2 TP3
TP4
TP6 TP7 TP8
DC
R
1
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2
5
R
3
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R
TP2 TP4 TP5
TP1
TP3
TP6TP7