The IR runs "continuously" on the GP2D12 (rather than being one-shot) but my impression is that it uses pulses so you're almost certainly right about the IR pulses pulling down the power. The reason it's being pulled down so far is probably because of the resistance of the supply line (at a guess). Cheers, Zik On 04/06/06, Darren Gibbs wrote: > Hmmm... I didn't catch that on the website, but I don't think that's > what's going on here. The two distance sensors are fixed and pointed > in opposite directions on different levels of the stairwell between 3 > and 10 feet apart vertically (different on each flight of steps). > The two Sharp parts seem to be working fine themselves, I get good > measurements from them... it's just that having them powered from the > same supply as the motion sensor causes the motion sensor to not work. > > When I hook up a scope to the +5V lead at the far end of the cable, > it looks beautifully flat when nothing is connected. When I connect > a Sharp sensor, I start seeing 1V dips every 1ms. Same thing when > two are connected. I also see ~1V pulses on the signal output every > 1ms. The data sheet says the Sharp parts update every 32ms, maybe > they're sampling every ms and averaging? I thought maybe the 1ms > illumination pulses were pulling down the supply, but if the IR > shines continuously that doesn't make sense. > > > On Jun 3, 2006, at 5:49 PM, Zik Saleeba wrote: > > > GP2D12s send out a continuous stream of infrared. When two of them can > > "see" each other's beams interference occurs. The solution is to use a > > different model such as the GP2D02 which allows you to sample on > > demand. > > > > Here's a piece from the acroname web site: > > "The GP2D12 and GP2D15 ... fire continuously and don't need any > > clocking to initiate a reading, they are easier to interface but use > > more power and can potentially interfere with one another when > > multiple detectors are used on a single robot. Interference can be > > avoided with the GP2D02 and GP2D05 because the microprocessor can > > control when they fire." > > > > http://www.acroname.com/robotics/info/articles/sharp/sharp.html#s4 > > > > Incidentally I got caught by this one too. I'm now using GP2D02s. > > > > Cheers, > > Zik > > > > On 04/06/06, Darren Gibbs wrote: > >> I wonder if anyone could help with an insight into this situation... > >> I'm out of my debugging depth at this point. > >> > >> I'm working on a project with several remote sensors. On each of 4 > >> flights of stairs there are mounted two Sharp GP2D12 IR distance > >> sensors (pointed lengthwise to detect a stepping foot anywhere on the > >> monitored stair) and a KC7783 IR motion sensor to detect activity at > >> the doorways. Both of these parts operate at +5V and are connected > >> to to a 5V 5A power supply. The distance sensors output an analog > >> voltage (2V range), and the motion sensor TTL. The distance sensors > >> draw 33mA each and the motion sensor 400uA. > >> > >> When the three sensors are all connected near (within a foot of) the > >> power supply, they all work fine. > >> When connected at the end of about 60' of CAT5, the motion sensor > >> refuses to work and I see low frequency noise on all three sensor > >> outputs. > >> If I power the motion sensor right at the 5V supply, but leave the > >> distance sensors at the far end of the long cable, they all work > >> fine. > >> If I leave the motion sensor at the far end of the cable, but power > >> the distance sensors right at the supply everything works fine. > >> If I leave all three sensors at the far end of the cable, power the > >> distance sensors right where they're mounted using a 9V battery + > >> LM7805, and power the motion sensor from the 5V supply at the near > >> end of the cable, all three work fine. > >> > >> The only non-working configuration is all three devices at the far > >> end of the cable, with all three powered through the cable. > >> > >> I'm wondering what the distance sensors could be doing to the power > >> supply from the far end of the cable that would cause the motion > >> sensor to crap out, but not have that effect on the near end of the > >> cable. Is there something about running the power to those device > >> through the 60' of wire that would make such a difference? > >> > >> Any suggestions much appreciated! > >> -- > >> http://www.piclist.com PIC/SX FAQ & list archive > >> View/change your membership options at > >> http://mailman.mit.edu/mailman/listinfo/piclist > >> > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist