Need help with Sensor

[Hop_of_752]

When we power the detector with 5V and ground and look at the voltage of the output from the detector out, that is the output is not connected to the RC, just the meter, we seem to detect a change from 5 V when there is no signal from the beacon and 4.4V when there is a signal. Is this right? Can someone explain what is going on?

[Marc P.]

I believe the IR recievers are setup to output a low voltage as positive confirmation of a signal. This means with no IR signal, it will output 5 volts. When there is and IR signal, it will output a lower voltage (ideally 3.3v I believe, as per the spec sheet of these sensors).

If your sensors are outputting a lower voltage with no signal, it could mean a number of things- damaged recievers, IR noise/reflection, unstable input voltage, or something of the like.

[Random Dude]

Originally Posted by Marc P.

I believe the IR recievers are setup to output a low voltage as positive confirmation of a signal. This means with no IR signal, it will output 5 volts. When there is and IR signal, it will output a lower voltage (ideally 3.3v I believe, as per the spec sheet of these sensors).

If your sensors are outputting a lower voltage with no signal, it could mean a number of things- damaged recievers, IR noise/reflection, unstable input voltage, or something of the like.

Actually the spec sheet says that the maximum output voltage when it sees a signal is 250mv.

That being said, if you are just using a simply volt meter, you will most likely not see anything near 0v, but some other voltage (Possibly around 4.5v for the type 0 beacon since it is only on for 10% of the time. Beacon 1 would be slightly slighty lower, say 4v due to it's 20% duty cycle)) Exactly what may vary from that though, depending on your meter.

[Marc P.]

Originally Posted by Random Dude

Actually the spec sheet says that the maximum output voltage when it sees a signal is 250mv.

That being said, if you are just using a simply volt meter, you will most likely not see anything near 0v, but some other voltage (Possibly around 4.5v for the type 0 beacon since it is only on for 10% of the time. Beacon 1 would be slightly slighty lower, say 4v due to it's 20% duty cycle)) Exactly what may vary from that though, depending on your meter.

Whoops, my mistake. I guess that's what I get for reading spec sheets late at night

I think we saw our recievers outputting 3.3v, but that was before we found a couple of things wrong with the beacon. Now we are indeed seeing 4.5v with the type 0, and 4.0 with the type 1. Thank you Kevin, for all the work you've done!

[Hop_of_752]

Thanx everyone for ur help/input!

[Kevin Watson]

Originally Posted by Hop_of_752

When we power the detector with 5V and ground and look at the voltage of the output from the detector out, that is the output is not connected to the RC, just the meter, we seem to detect a change from 5 V when there is no signal from the beacon and 4.4V when there is a signal. Is this right? Can someone explain what is going on?

Hey, this is very cool because this is exactly what you should be seeing. With the beacon present, the meter is averaging the the output of the sensor over time. An ideal meter when measuring a +5 volt pulse train will register a voltage equal to 5 * (on time/total time). The output of the sensor, when viewing the type-0 beacon, is on for 9.0ms of every 10ms. plugging this in to the equation results in a voltage of 4.5. On the other hand, the output of the sensor, when viewing the type-1 beacon, is on for 8.0ms of every 10ms. plugging this in to the equation results in a voltage of 4.0. I'll bet your sensor was pointed at the type-0 beacon when you measured your 4.4 volts. If both beacons are in view of the sensor, the voltage will be even lower (3.5v). You can find an illustration of the sensor output here.

-Kevin