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In my project I am using multiple PIR Sensors. I am providing power using the 5v pin number 2 and also using 3 Signal Pins for receiving. I noticed that if all three sensors are plugged in, then the range on the sensors is only about 3 feet. If I remove all but one, then the range goes up to right around 15-20 feet.

Seems to me that with all three sensors drawing power at the same time, that perhaps there is not enough power to supply full range? Is that so and if yes, what do you recommend. I am already using a power supply of 5.1v and 2A

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    I'd have thought the PIRs would be drawing a few milliamps, not enough to affect each other. Could you post a link to the specs? How are they positioned in relation to each other? – joan Apr 29 '14 at 5:21
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    That is what I thought too. They do not draw much at all while in standby. I do not use active polling for the sensing function. Even if they all three would be triggered at the same time, it should not be bad. Right now all three are connected direct to GPIO2 and 26, just for testing. I will end up connecting one each to their own signal pin, but that does not draw power. The PIR are standard ADAFruit sensors, so nothing special there. The only other thing that is connected to that 5v circuit is an audio amp, but it is also not like that runs constantly. It is only used for beeps and not even – user14105 Apr 29 '14 at 10:49
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    We would need to models of the PIR sensors. But also, you are connecting the 5V direct to power supply, right? Not via Pi. And just to double check, you are connecting parallel and not in series (just checking)? It sound like a power issue anyway. – Piotr Kula Apr 29 '14 at 11:40
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    How did you connect them? Could you show us a picture of the wiring, or some schematic? – Gerben Apr 29 '14 at 16:25
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I had a similar issue where I was combining a 5V DC relay and PIR sensor off the same 5V GPIO pin. My power supply didn't provide enough amps and with WIFI and a keyboard my RPI model B would get low on juice. You're probably just powering via a USB power supply and wiring the PIR sensors into the same GPIO pin. For more complicated, power hungry projects it helps to break the power supply out so you can power the devices directly from the power source, and make sure it has enough 5V DC amps. (like 2A or 3A, though all 3A power supplies will be laptop style with a brick)

Explaining how you wired the PIRs up would help.

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As stated in the comments to the question the PIR sensors are standard ADAFruit sensors. The description points to a similar product: Parallax PIR sensor. The relevant product detail:

Current requirements: 130 uA idle, 3 mA active (no load)

So it is hardly conceivable that the power consumption of those three devices is too high for the respective supply.

Checking and explanation of the wiring and the setting of the GPIO ports is required to solve the issue.

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