DASL 120Introduction to Microcontrollers

Lecture 4

Introduction to Circuit Prototyping

Introduction to Circuit Prototyping

• Introduction to Circuit Prototyping

– Bread-boarding

– Soldering/de-soldering

– Making cables

– Wire-wrapping

– Testing wire and trace connections

Breadboards

• Overview– Array of traces set into a perforated board in which

wires connect

– Solder-less method of constructing circuits

– Used to break out the pins of a IC to isolate or increase connections to the pins

• Components Needed– Breadboard

– Jumper wires

– Other circuit components

Breadboards (cont.)

• Breadboard Connections– Rows of connections are

used for power or ground connections to multiple components

– Columns of connections are used to break out pins of ICs, which lay horizontally across the board

Microcontroller

Soldering

• Overview– Used to make permanent electrical connections between

conductive surfaces of components– Tin alloy is used as the bonding material to physically

adhere the surfaces– Connections are solid until heat is applied to the joint, at

which point the tin solder melts and the connection is broken

• Components Needed– Soldering iron– Tin solder– Flux– Components to be bonded

Soldering (cont.)

• Technique– First apply alcohol solution to traces/wires to remove

debris from the surface– Place the soldering iron on the joint and wait for the

surface to heat, at which point apply tin solder to the joint– When soldering wires, apply tin solder to each wire and

then hold the wires together and heat the joint to bond the wires

– When soldering a wire to a pre-soldered joint, do not apply solder to the joint without melting the joint beneath the new connection (cold joints)

– Be sure to clean the tip of the soldering iron after creating a joint

De-soldering

• Overview

– Used to remove tin solder from joints to remove or replace wires, ICs, etc.

– Makes use of a de-soldering braid or de-soldering pump to remove liquid solder from the leads of a joint

• Components Needed

– Soldering iron

– De-soldering braid/pump

De-soldering (cont.)

• Technique

– Apply the soldering iron to the joint and heat the solder until it is liquid

– Apply the de-soldering braid or de-soldering pump to the joint and remove the solder from the joint

– The above step may need to be repeated several times to remove all or most of the solder

Making Cables

• Overview– Used as detachable connections between electrical

components– Cables have terminated wire ends which allow for

detachable connections

• Components Needed– Wire– Wire connectors & inserts– Wire clippers– Wire stripping tool– Connection-lead crimping tool– Soldering iron (optional)– Tin solder (optional)

Making Cables (cont.)

• Technique– Begin by isolating the wires needing to be terminated (if

the wires are within a larger cable, first strip back the outer cable)

– Strip back the wires to expose the leads (for small diameter wires, fold over the leads and apply solder to increase the size of the lead)

– Use the wire crimping tool to crimp the wire insert to the wire lead (optionally heat the insert when attached to melt the solder to the insert for a better connection)

– Push the insert into the wire connector to complete the plug

Wire-wrapping

• Overview– Solder-less method of making connections

– 30 gauge wire wound around pins to create non-permanent wire connections

– Not recommended for high-current applications

• Components Needed– Wire-wrapping tool

– 30 gauge wire wrap

– Male header pins

Wire-wrapping (cont.)

• Technique

– Begin by stripping back the covering of the wire wrap (the wire-wrapping tool has a 30 gauge wire stripper inside the handle)

– Insert the wire wrap into the hole near the edge of the tip of the tool and into the groove along the side of the tool

– Place the center hole at the tip of the wire-wrapping tool over the male header pin, hold the wire wrap still, and twist the tool until the wire is secured to the pin

Testing Electrical Connections

• Verifying Connections

– After electrical connections are made, it is beneficial to verify that the connection is solid

– Use the resistance setting of a multimeter to determine that the connection is not broken (the resistance will read “0” if the connection is solid, and float between values if the connection is broken)

Announcements

• Midterm next week

• Homework and study information will be online between this evening and tomorrow evening

• Midterm will cover material from the past four lectures