Optical ICs solve position-measurement problems

Two new optical-detector ICs from Hamamatsu Corp can help you with proximity- and position-sensing challenges. The S8158 circular-position-sensitive IC detects the angle of light that is incident to its surface, to within 0.01° over a range of ±174° from the nominal 0° reference line, for nearly a full circle of coverage (Picture). The six-pin IC, which measures approximately 4×8 mm sq, including leads, generates a pair of currents from its two photosensors. To determine the angle, you divide the difference of the currents by their sum and then apply a scaling factor. You can do this operation with analog front-end circuitry, an A/D converter, and a processor or simply by using just a few more op amps. Spectral response spans 320 to 1100 nm, and output at the 960-nm peak-sensitivity wavelength is 0.55A/W. The $2.50 (OEM quantity) photo device also features dark current of 0.05 nA and a typical rise time of 10 µsec.

If your need more conventional proximity-detection and linear-range-finder functions, the S8020 IC integrates all the elements except the external infrared LED and lenses. The 4×8-mm, surface-mount device or the similar through-hole S8064 version each include an LED-drive circuit, dual photodetectors, and control/detection circuitry with analog-voltage output to detect the distance to an object as far as 70 cm away, using basic triangulation principles. The visible-light filtering of the package improves performance in ambient light, as does the pulsed drive and synchronous detection scheme. Operating from a 5V supply, the device typically consumes 4 mA of current and offers peak sensitivity of 850 nm. In either package, the range-finder IC costs $2.78 (OEM quantity).

Hamamatsu Corp, 1-908-231-0960, www.hamamatsu.com.