Want to add some robots to your Halloween party plans? Even better, how about some robot “bugs” dancing around the candy bowl? Then Boo, the light-loving bug bot, might be for you.

Derived from Randy Sargent’s LM386-based Herbie “photovore” robot, with some circuit enhancements supplied by Dave Hrynkiw and Mark Tilden, this bug robot can be easily built for less than ten bucks (or free if you have some spare parts in your workshop).

Self-contained within a discarded DB-9 serial hood, Boo waits passively until some bright light catches its eye. Then it’s showtime. The illumination triggers a tiny vibrating motor embedded in this bot’s abdomen, and it’s off to the races. If the jig the bug dances is not your cup of tea, slip a rubber grommet over the hub of the motor’s spinning weight to give Boo some cockroach speed.


A small robot bug.
The finished bug bot. Dave Prochnow
  • Time: 3 hours
  • Cost: free or, if you purchase all new parts, $8.49
  • Difficulty: easy


Various electronics parts for building a robotic bug.
The bug bot’s parts. Dave Prochnow
  • LM386 (DigiKey #LM386N-1-ND; $1.09)
  • CR2032 coin cell battery (local purchase; $0.25) or, try these rechargeable 3-volt batteries (SparkFun Electronics #PRT-08818; $4.95)
  • 24-millimeter coin cell holders (DigiKey #BH2430T-C-ND; $0.95)
  • KobiConn solder cup male plug DB-9 shell size (Mouser #156-1815-E; $1.80)
  • KobiConn black economy plastic locking hood DB-9 series 156 (Mouser #156-2010-E; $.65)
  • 2 (47K) ohm resistors (DigiKey; $0.27)
  • 2 CdS photocells (The Electronic Goldmine #G14025; $2.49)
  • Pager motor (BG Micro #MOT1030; $0.99)
  • Scrap wire


1. Build your bug bot according to the Hrynkiw and Tilden schematic without the “run away” relay circuit addition. Refer to their book, Junkbots, Bugbots, and Bots on Wheels for complete assembly instructions.

2. Glue the battery holder to the top of the DB-9 hood. Route the positive and negative terminals inside and connect them to the LM386.

3. Use the solder cups on the inside of the DB-9 male plug for attaching the resistors, positive and negative leads, and circuit wiring connections for pins 2 and 3 of the LM386 and the external CdS photocells.

Two photocells that serve as a bug bot's eyes.
The photocells serve as the bug bot’s eyes. Dave Prochnow

4. Connect one lead from the pager motor to pin 5 of the LM386 and the other motor lead to the negative terminal of the battery holder.

5. Assemble the DB-9 hood and mount the pager motor externally through one of the hood’s machine screw connectors.

6. Plug the two CdS photocells in the appropriate pinouts of the DB-9 used in Step 3 for connecting pins 2 and 3 of the LM386.

7. Slip a battery into the battery holder and get ready to make this bot boogie. Shine a bright light on the CdS photocells of Boo and watch it dance the macabre writhe of a “spooky” bug bot.

Here’s a quick video of the bug bot jitterbugging.