PIR to Gemma v2?

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btrnuthatch
 
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PIR to Gemma v2?

Post by btrnuthatch »

I'm a newbie. With Gemma v2 I can control Flora RGB Smart NeoPixels running with battery power. I want to initiate power to the NeoPixels with the adafruit PIR. Do I need to use a MOSFET? Or what? I tried to go battery to PIR to Gemma but it won't work so I'm guessing I need an additional component. I hope this makes sense. Thanks.

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adafruit_support_carter
 
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Re: PIR to Gemma v2?

Post by adafruit_support_carter »

The basic idea of using the PIR sensor:
https://www.adafruit.com/product/189
is to read it via a digital input. The output of the sensor is 3.3V, so you can connect it directly to one of the digital inputs of the GEMMA. However, it needs 5V power. You can get this off the VOUT pin if you're running from USB. For running off battery, VOUT will be the battery voltage, so need you'd need to figure out how to make that be 5V.

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

Well, I haven't been able to understand/figure out how to get 5V out the VOUT running with batteries.

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adafruit_support_bill
 
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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

What kind of batteries are you using? A 3xAA pack is 4.5v, which is close enough to 5v for the PIR. If you are running from 3.7v LiPo, then you may need to use something like a PowerBoost 500. https://www.adafruit.com/product/1903

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

Thanks. I will order and try both. And then I'll be back to report (my success I hope).

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

From batteries regardless of 5v or 7v, the output of the PIR is 1.46 to the PowerBoost 500 that then ups the output to 2.46. Is that all I can expect? This still obviously won't drive the Gemma or Circuit Playground (which is what I'm trying to do). Help please. Thanks.

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adafruit_support_bill
 
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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

2.46v is a logic HIGH to a 3.3v processor like the Gemma. So that should work fine.

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

I should not have said "obviously" as nothing is obvious to me in this domain. Thanks for that. Now I see that I can get power to the Gemma as the green light is on. My new problem is not being able to provide enough power to a NeoPixel from the Gemma; I only get 1.86 out of the Gemma.
It seems the problem I'm facing is the low output from the PIR even with the Powerboost. Is there something else I should be doing to the PIR output to get more power? Will a simple shortening of the wiring help? I'm using alligator clips now. Or what?

With my very limited understanding, I'm about to give up. I can provide the necessary power to the Gemma directly via battery. I simply thought inserting the PIR in between battery and Gemma would be easy. Woe is me. Thanks again.

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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

I simply thought inserting the PIR in between battery and Gemma would be easy.
Are you trying to power the Gemma from the PIR? That will not work. The output of the PIR is a logic signal. It is not a power source. You need to connect the PIR output to a digital pin on your Gemma and read it in your program.

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

OK. Well, I wish I knew that; I don't know enough to have known that. I'll look into the "digital pin" solution and how I can "read that into" my program. If there is an easy pointer to this, I'd appreciate that. Otherwise, I'll try to bumble my way through. Thanks again.

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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

Here are the Gemma pinouts. You can connect it to D0, D1 or D2 - whichever is free.
https://learn.adafruit.com/introducing-gemma/pinouts

And this is how you read a signal from a digital pin.
https://www.arduino.cc/reference/en/lan ... gitalread/

If you provide us with more information like the code you are using and a photo showing all your connections, we can probably offer more specific advice.

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btrnuthatch
 
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Re: PIR to Gemma v2?

Post by btrnuthatch »

Thanks for the pointers. At this point, I don't have a program as I'm stuck at trying to power up the Gemma to light up Neo Pixel. If/when I get to that point after digesting your pointers, I'm sure I'll be back. Thanks again.

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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

I'm stuck at trying to power up the Gemma to light up Neo Pixel.
Just connect it to your battery. Then write a program to read the PIR signal and light up the Neopixels when it turns on.

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Re: PIR to Gemma v2?

Post by btrnuthatch »

Sorry, I meant "stuck trying use the PIR to power up the Gemma to light up NeoPixels." I can make the Gemma work with NeoPixels without the PIR. Sorry if my post was confusing.

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Re: PIR to Gemma v2?

Post by adafruit_support_bill »

The PIR is not a power switch, so it can't power up anything like the Gemma without additional circuitry. You could use the PIR output to turn on a transistor to switch power to the Gemma.

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