>
> I think that that might be referring to the logic circuit. The LED
> requires more (see section 7-9). As you have seen from the data
> sheet, this sensor has 5 wires. One pair supplies the logic circuit
> and the other supplies the LED.
>
Hmm... The way I understand these sensors is that they pulse the LED
and this does require several times the normal AVERAGE current. But,
in the long term, the AVERAGE current is in the 30-50 mA range.
So, most designers put a fairly large electrolytic capacitor (33 ufd
or more) immediately adjacent to the sensor to prevent the current
spikes from wandering around the PCB. It would also be good to put a
0.1 ufd ceramic at the same point. These want to be as close to the
sensor as possible.
Look at this schematic for the MiniSumo Mark III
http://www.junun.org/MarkIII/datasheets/Controller_SCH.pdf
At grid B5
are the 33 ufd capacitors for the GP2D12's that are connected to J5 &
K6 (grid C6). On the PCB, these capacitors are mounted immediately
adjacent to the connectors.
HOWEVER, this is all a guess! I don't have any of these sensors so I
can't just take a simple measurement. But you can...
Section 7-9 has the word 'peak' for the LED current. This implies
that it is pulsed. What they are talking about is having a power
supply that doesn't go into overcurrent foldback when it sees the peak
current. But handling peak currents is the reason for bulk
capacitance like those electrolytics.
Richard
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