Mousey the Junkbot: Bug Report & Troubleshooting Ideas

Mistake Found in Sensitivity Subcircuit: A builder, Gareth Adams, has brought to our attention a mistake in the subcircuit for adding sensitivty to Mousey's input sensors. Wilf Ritger, creator of the circuit hack, pointed out on the Yahoo! BEAM group that the circuit as I have it in my book, and as it appeared in Dave Hrynkiw's Junkbots, Bugbots, & Bots on Wheels (which is where I got the hack) is incorrect. The current circuit diagram shows the correct wiring. PLEASE NOTE: This means that the breadboarding illos and photos on the site are also incorrect. Please refer to the circuit diagram when breadboarding. If you've already built Mousey with the incorrect connections, it shouldn't be a big deal to reconnect them as shown. Thanks to Gareth (not me, the other one) for finding this bug.

Tire Hack Several people have emailed me about how to create rubber tires on Mousey's motor shafts. Here's the skinny. It's easy!

Mistake in Circuit Diagram!: The Mousey Circuit Diagram in the book has a mistake in the emitter eye hookups. Here is the corrected image. Somehow the beveled edges on the IR emitter packages got switched during illustrating and I didn't notice during editing. The leads on the emitters aren't labeled, but because the bevel indicates the cathode (-) side, it looks like you're supposed to hook the cathodes to pins 2 and 3 on the op-amp chip and the anodes (+) to power. Oh contraire! You want to hook the anode (+) sides to pins 2 and 3. It gets confusing because of the whole "reverse biasing" technique used here (running power through the emitters in reverse to make them more photoconductive). Just remember that you want the negative emitter leads to go to power and the positive leads to go to the pin 2 and 3 inputs (it's counterintuitive, but that's what you do). In the book, we recommended soldering a red wire onto the cathode lead on each emitter and a black wire to the anodes, and then just treating the wires normally (red wires plug into power, black into the chips input pins). Don't know if this helps or confuses matters. Thanks to builder "Mousey Fan" for catching this error. Sorry about the confusion. Barbie sez: "Building robots is hard!"

Switch Clarification: In the book, we were somewhat unclear about figuring out what terminals on a switch you should connect to if the switch has more than two. This should clear things up.

Motor Connections Clarification: As we said in the Troubleshooting section of Chapter 8, you may find, after Mousey's hooked up, that one, or even both, motors turn in the wrong direction. We said to switch the motor wires. Just to be clear, we mean switch them at the terminals on the motors themselves. So, if the left motor is turning in the wrong direction, desolder the red and black wires where they are attached to the two motor terminals and switch them around (and resolder). That should do the trick.

Intimidated by the WiringWe know the photographs in the book for the freeform soldering of Mousey's innards are not as clear as they could be. Hopefully, the larger images here on the site will help. We hope to update the on-site images soon with color highlighting over the wire connections in each step. Though it may look like a jumble, hopefully after breadboarding the circuit and studying the circuit diagram, the photos will make more sense. It's actually a rather simple circuit. It just looks like a tangle of plastic spagetti.