HEXBUG nano is a fun toy which moves like a real bug. I want to use it to surprise someone who open the box contain a dozen of the HEXBUG nano. But the HEXBUG have only a toggle switch for activation, so the bugs cannot hide silently in the box.
We can add a photo switch to activate the bugs only when they come to bright place. It works well, and the modification doesn't change the look of HEXBUG nano.
It is very simple circuit, but little difficult when you solder SMD transistors. Check the schematics.
Step 1: What you need
1. A HEXBUG nano
You need the HEXBUG nano. I recommend the one which has clear window on the top.
2. SMD Transistor
I have tried 2SC4116 and 2SC3325. 2SC3325 is better because it has bigger body and larger collector current.
3. Photo diode
I used PS1101W.
4. A design knife
You need it to uncover the bug.
5. A screw driver (+)
You need it to remove battery cover.
6. Soldering iron and solders
You need them to build the circuit.
7. A tweezer
The parts is very small. You need it.
8. A mini knipper
You need it to cut off the wire of the toggle switch.
9. A double sided tape
You may need it to hold parts when you solder them.
10. A instant glue
You need it to bond the bug's cover and body.
Step 3: Mount the photo transistor on the tape
PS1101W has a emitter mark (green) on the edge. The photo shows the emitter is bottom.
Step 4: Solder the transistor to the photo transistor
Then solder the photo diode's emitter to the transistor's base.
The photo shows the soldering steps. The photo transistor's emitter is bottom side.