Sensors
Posted: Thu Nov 17, 2005 8:41 pm
With reference to Adam's question about sensors in the Antweight thread, thought I'd kick something off here.
There are two main ways of doing opponent sensing: ultrasonic and infra-red (IR). Both work on the principle of reflection, ultrasonic uses sound, IR uses light.
For my minisumo robot I am going to try IR. To avoid problems with ambient light I am using IR modulated at 38kHz with a synchronous detector which can effectively filter out ambient light and other infra-red. This all comes in one handy IC, the IS471F from Sharp. It's available from Farnell and several online robotics suppliers. Just add an IR LED, resistor and capacitor.
This gives a "yes/no" detection of an opponent within range. It doesn't give any indication of range.
For an analog IR range-finder, the Sharp GP2 series are popular, but more expensive than the IS471F. Farnell stock several, including stock code 9707859 which gives an analog output over the range 4-30cm. Other ranges are available.
The IS471F soultion costs about ?2.50, whereas the GP2 devices are nearer ?10. Of course, you need (at least) two sensors to detect front/left and front/right to find your target.
I haven't looked at ultrasonic methods in detail, but basically it works like radar - send out a "ping" and wait for the echo to come back. Distance is then proportional to time.
There are two main ways of doing opponent sensing: ultrasonic and infra-red (IR). Both work on the principle of reflection, ultrasonic uses sound, IR uses light.
For my minisumo robot I am going to try IR. To avoid problems with ambient light I am using IR modulated at 38kHz with a synchronous detector which can effectively filter out ambient light and other infra-red. This all comes in one handy IC, the IS471F from Sharp. It's available from Farnell and several online robotics suppliers. Just add an IR LED, resistor and capacitor.
This gives a "yes/no" detection of an opponent within range. It doesn't give any indication of range.
For an analog IR range-finder, the Sharp GP2 series are popular, but more expensive than the IS471F. Farnell stock several, including stock code 9707859 which gives an analog output over the range 4-30cm. Other ranges are available.
The IS471F soultion costs about ?2.50, whereas the GP2 devices are nearer ?10. Of course, you need (at least) two sensors to detect front/left and front/right to find your target.
I haven't looked at ultrasonic methods in detail, but basically it works like radar - send out a "ping" and wait for the echo to come back. Distance is then proportional to time.