Nuts and Volts - July 2014

3. Solder all of the remaining anode pins together. This anode pin bus will be connected to V+ during a later step.

4. Turn the LM3914 over and upside down (i.e., “dead bug”). Nest the IC neatly between the anode pin bus and the cathode pins.

5. Carefully solder pins 18-11 of the LM3914 to the adjacent cathode pins. These cathode pins are for LED 2 through LED 9.

6. Solder pin 1 on the LM3914 to the LED 1 cathode.

Now, LEDs 1-9 on the LED bar graph are connected to the LM3914.

7. Solder pins 6 and 7 on the LM3914 together, then connect a 1K resistor between these joined pins and ground (GND).

8. Connect the LM3914’s pins 8, 4, and 2 to GND.

9. If you don’t like the dot mode display for the desktop rocket, you can optionally connect pin 9 on the LM3914 to V+. This connection will enable bar mode display on the LED bar graph. In bar mode, all LEDs remain lit as the potentiometer is turned.

10. The signal source input is provided by the 5K potentiometer. The middle wiper contact on the potentiometer is connected to pin 5 on the LM3914. One of the two remaining potentiometer contacts is soldered to V+ and the final contact is soldered to GND.

11. Carefully push the two blinking LEDs through the cardboard rocket’s nosecone. The anodes of the LEDs are both connected to V+, whereas the cathodes of the blinking LEDs are connected to pin 10 of the LM3914.

12. The final step is to add the battery power. All GND connections are routed to the negative terminal (-)

■ The "business" end of the desktop rocket without lighting any fuses. Note: The LM3914 is fixed upside down and "dead bug" between the cathode/anode pin rows of the LED bar graph.