154 4 damentals Industri I d d s ia l l Rob bo tics s Fu un Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. 3. Place about 2″ of the end of the cold-rolled steel bar into the coil. ″ 4. Close the SPST switch and describe what happens to the cold-rolled steel core. To prevent the coil from heating, do not allow the SPST switch to remain closed for more than 20 seconds. 5. Place the bar inside the coil and close the SPST switch. Try to remove the bar with the power on. Describe what happens. Do not allow the coil to remain energized for more than 20 seconds. 6. How could the above solenoid be used as a pusher or puller coil? 7. Disconnect the circuit. 8. Acquire a door chime assembly. Examine it to determine if it is to be powered by 6, 12, 18, or 24 volts. Record the voltage used for the chime assembly. 9. Remove the protective chime cover to expose the spring-loaded solenoids and solenoid connections. Measure and record the resistance of the solenoid coil. 10. There should be three solenoid connections. One will be common to the other two. Connect the common connection and either of the remaining connections to the power supply. + – Air-core coil Cold-rolled steel Goodheart-Willcox Publisher Air-core coil and steel core. + mA SPST Common connection Chimes Goodheart-Willcox Publisher Solenoid circuit with door chime.