In some cases, soldering is necessary. Build very high frequency,
low noise, high power or high voltage sections to plug into the SBB.
You can build something like a triac power control directly
on the SBB, but the dangers of the exposed line voltages should be considered.
Power components such as resistors, lamps, TO-220 transistors
and regulators, may run hot enough to damage a SBB.
Some power devices can be raised above the plastic of the SBB
or heat sinked to reduce damage.
If necessary, float parts above the SBB after soldering them
together. These parts can be put on the back of the PCB version.
Solder resistor leads to panel pots and switches to allow them
to plug directly into the SBB.
Dos and don'ts
Don't forget the center jumper when using a SBB with split power
busses.
The center jumper can be left out of a power bus. This allows
2 power busses such as - 5 Volts power for the input stages and -15 Volts
for the output stages or +9 Volt battery with 5 Volts regulated from it,
etc.
Use the top bus, typically +15 Volts, for battery input with
the +5 Volt bus regulated on board from it.
Never force an oversize lead into a contact. The maximum wire
size is 20ga (.032" diameter).
Never solder to a wire while it is plugged into a SBB contact.
Twist the leads on TO-220 power tab devices to safely plug into
SBB without damage to the contacts.
Peel back the backing tape to repair a sprung contact or a contact
strip plugged by junk. A sharp knife can slit a small area to expose just
the damaged contact.
Avoid too small wire. Wire should be 26 ga (.015" diameter)
or larger. Tinned 28 ga ribbon cable is marginal in size for a reliable
connection.
Keep op-amp virtual ground short. This means it should be no
more than the single contact connecting to the pin of the op-amp. Put the
feedback resistor in the "output" part of the circuit.
Multiple SBB's
More than one SBB can be used for more complex designs. Power
and signal routing get more critical and difficult in these designs.
Sometimes, a ground loop can be reduced by adding a ground from
one SBB to another SBB right where the signal is produced on one SBB and
used on the second SBB.
Use a bus bar for the ground between SBB's. A large gauge wire
is necessary. Something like 14 ga. solid electrical wire with its insulation
stripped should work.
Power and ground
Because of the limited ground bus in the SBB, ground loops can
cause severe problems if not prevented by proper layout of the circuit.
Low level inputs should be on the left of the SBB, high level
outputs should be on the right side. This is like a schematic is normally
drawn.
Power should come into the SBB on the right end of the SBB at
the high level portion of the circuit.
Bypass, bypass, bypass!
Bypass each power bus with a bulk capacitor right where the
power comes into the SBB. Use from 10uf to 100uf tantalum capacitors.
Bypass with ceramic capacitors at every IC power pin or amplifier
stage.Use 0.01uf to 0.1uf capacitors.
Add more bulk bypass capacitors at power stages.
Bypass on the output side of an amplifier to prevent the bypass
current from flowing through the signal ground.
Keep the outputs on the output side and the right side of amplifiers
to prevent oscillation caused by ground loops and capacitive coupling.
The LM318 is especially prone to oscillation when capacitively
loaded on its output if the output is poorly routed and/or a ground current
is allowed to flow through its input circuit.
Use a solder lug to connect from the ground bus to a mounting
hole thus grounding the circuit to its metal case.
Allow for extra bypass caps whenever possible.
Contact capacitance
There is about 10 to 15pf of capacitance between adjacent contact
strips. This capacitance can have a large effect at high frequencies.
Ground the contact between crystal leads with 0.2 inch spacing.
The contacts can act as the crystal loading capacitors.
3 pin ceramic resonators wire just like a crystal. The center
lead is connected to the internal caps of the resonator.
Crystal and ceramic resonator caps can go to a properly bypassed
power bus if it is easier to wire.
Contact capacitance at the input of an op-amp can cause it to
be unstable. Add a small cap (5 to 10pf) across the feedback resistor to
reduce this effect. This cap reduces the amplifier's bandwidth.
Keep the input of an op-amp as few contacts as possible to minimize
the input capacitance.
Low impedances are faster than high impedances.
Bootstrap a contact to reduce input capacitance.
The input capacitance of an IC pin is about 5pf. A socket will
add to that capacitance as well as add capacitance between adjacent pins.
Do not use IC sockets in high speed portions of a soldered board.
The single sided PCB makes it easy to unsolder and replace IC's.
The soldered board has lower capacitance between "contacts"
than the SBB. Values of small value capacitors may have to be increased
when a soldered board is constructed.
Reduce capacitive coupling by leaving an open, unused contact
between signals. For example, bend transistors with a space between the
collector and base leads to reduce Miller effect.
Shields
Use grounded contacts to act as shields. A properly bypassed
power bus can also work for connecting a shield and may be easier to wire.
What shields are used for:
Keep fast digital signal edges from
coupling into analog circuits.
Isolate inputs from outputs in high
frequency circuits.
Isolate inputs from outputs in high
gain amplifiers.
Reduce feedback capacitance in common
emitter transistor amplifiers.
Spread the leads by one hole to allow
shield between collector and base.
Shields add capacitance that slow digital edges and reduce bandwidth
of amplifiers. Sometimes this is is desirable and sometimes it isn't.
A power contact can act as a free shield (with properly bypassing).
The power leads of an op-amp are a good example.
Add a ground plane plate. The ground plane is sort of a shield
at the price of lots more capacitance on all the contacts.
Other hints
When using a static sensitive part, build the circuit around
a part of the same size that won't be damaged by static. Remember to change
to the real part before applying power!!!
Don't be afraid of changing grounding or component layout. This
is why you are using a solderless breadboard.
Try not to run jumpers or place components over IC's. This makes
changing the IC difficult without rebuilding the circuit.
When parts overlap other parts on the SBB, they can be put on
the back of the PCB.
Keep all components tight against the board. This keeps leads
as short as possible and makes the circuit more reproducible.
Lead inductance is about 10nh for each inch of straight wire.
On a PCB, a via is about 0.5nh.
Use top adjust pots for easiest tweaking (tweaking?).
Use an LED on one of the power supplies as a power on indicator.
Input/output orientation of an IC or transistor is more important
than power orientation. Bypassing can "shorten" power leads.
Use DIP switches instead of rotary and toggle switches when
practical. The DIP switch fits directly into the SBB with requiring soldering
and mounting.
Place front panel pot and switches near the edge of the SBB
for best finger room.
Use Vector pin for connecting external wires and added bus wires
on PCB. The hole may have to be enlarged to accept the pin.
Resist the urge to "improve" the layout when transferring the
design to the PCB version. These changes seldom work as well as expected.
Get it right on the SBB first.
A test point can be made with a stiff, insulated wire 1 to 2
inches long.
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