ShokPopper & ShokPhoto-head
You want a simple Photovore? This very tidy design by Solarbotics' own Grant McKee is based on a technique developed by Mark Tilden - Shok
Here's video of the test robots being tuned as a 177kB Windows Media Format (WMV) file
or as a 168kB RealMedia (RM) file
(click for circuit diagram) - GrantM Aug 2001
Theory of operation:
"Shok" architecture is a technique pioneered by Mark Tilden describing controlled state changes of Bicore style circuits via chip power or enable toggling. When a Bicore circuit is powered on, it will resume a state opposite to what it was when it was powered off, this effect can either be duplicated by pulsing the enable line or by pulsing power to the chip itself. This is called "shoking" the Bicore. The power-on state can also be pre-determined by biasing the voltage across the Bicore capacitors. A photodiode attached directly across the Bicore charge capacitor will pre-bias the shoked output. The addition of tactile sensors is easily implemented by attaching a switch from the input of the Bicore to +Vdd. When the switch is closed, it forces that side high, presetting the state of the Bicore on the next pulse cycle.
Probably one of the simplest photovore circuits to date, the core circuit consists of a 6 part count and a solar-engine. Either 74AC240 or 74HCT240 will work but we recommend using the AC series for better output drive current. The ShokPopper will not work under battery power unless the enable line is pulsed.
Solar Engine to use with Shok:
The best solar-engine to use is the Miller engine. For the ShokPopper Photovore we used a Miller engine consisting of:
- CP3300uf cap
- CP1Âµf timer cap (0.47Âµf will work fine as well)
- 2N2222 Transistor
- SC3733 Solarcell
- D1 1N914 Diode
The Bicore Circuit Consists of:
- 74AC240 Octal Buffer Chip
- TR100k Trimpot
- 2 x 0.22ÂµF Capacitors
- 2 x IR1 Infrared Sensors
- 2 x RM1 Motors
- TACT2 Spring Sensor Kit (Optional)
The Miller engine switches the ground line of the circuit.
The theory of operating is very similar to that of the shok popper except that the head now only uses one motor, the photo head does not "lock" on but will continually seek for the brightest source of light. Nice effect if you want a continually seeking, dynamic device on a stationary base.
- 74AC240 Octal buffer chip
- 4 x CP0.1ÂµF capacitors
- 100k resistor
- 2 x 47k resistors