The Vishay TSSP58P38 looks like typical modulated IR receiver modules but is actually unique: it has an automatic gain control (AGC) that predictably sweeps from most sensitive to least sensitive so that you can get an absolute brightness measurement. To use the unit, illuminate the sensor with a burst of IR modulated at 38 kHz and measure the output pulse width: weak illumination (e.g. weak reflections from distant objects) will give a short pulse, while bright illumination will result in longer output pulses.
The datasheet suggests a relatively low update rate of two measurements per second based on a 120 ms IR burst followed by 380 ms for recovery, but in Pololu's basic tests, Pololu were able to get some meaningful measurements at up to 10 Hz. These sensors work nicely with Pololu's high-brightness 38 kHz IR proximity sensor modules; a pair of those along with a few stand alone sensors can enable sophisticated object detection systems.
These sensors are sold in packs of three units. Pololu also carry the similar TSSP58038, which has a fixed gain.
Modulated IR detector comparison
|Intended function||IR remote control||brightness/proximity sensing||predictable modulated IR presence sensing|
|Modulation frequency||56 kHz||38 kHz||38 kHz|
|Gain (sensitivity)||automatic but inaccessible||automatic, predictable||fixed high gain|
|Output||binary (data)||analog (pulse width)||binary (on/off)|
|Update rate||a few kHz||a few Hz||a few kHz|
- Operating Voltage: 2.5 V to 5.5 V
- Carrier Frequency: 38 kHz
- Package: Through-hole with 0.1″ lead spacing
For more information, see the TSSP58P38 datasheet (127k pdf).
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