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By: adafruit
nice thanks for the link too! you might want to check out fritzing parts, we just added a bunch for raspberry pi! https://github.com/adafruit/Fritzing-Library
View ArticleBy: Matt
Excellent. Just imported the library into my Fritzing installation. I like the parts for the PIR and membrane keypad. Will definitely be able to make use of the PIR part in future projects. I like the...
View ArticleBy: Graham T.
Great article Matt, very useful for a project I’m considering. Keep up the good work! G.
View ArticleBy: Richard
Cool stuff, good idea! But I get wildly fluctuating readings that don’t seem to change too much when I hold my hand over the sensor.
View ArticleBy: Alexk
Thanks for the nice article. I suppose the same method will work with an analog temp sensor. Thanks, alexk
View ArticleBy: Rick Seiden
I made some small changes to the code: from datetime import datetime GPIO.setup(PiPin, GPIO.IN) # Count loops until voltage across # capacitor reads high on GPIO startTime=dateTime.now() while...
View ArticleBy: Matt
In your example, with a 1uF capacitor, and multiplying the time by 1000000 I would expect the result to be 22. As it is 120 I think this just shows a delay in measuring the small time interval. Because...
View ArticleBy: Playing with GPIO and sensors on OpenWrt | #labOS
[…] There is a way to get analog reedings on GPIO with a simple RC circuit. […]
View ArticleBy: fmboy
Hi, Interesting article. I wonder if anyone used this approach to measure distance with sharp IR sensor on Pi? I get number of counts and from datasheet I can see that it takes ~38 msec to get one...
View ArticleBy: paul
Seems like a “dangerous” solution to me. Can the GPIO pin handle the inrush current created when discharging the capacitor which would have to rather large in order to get any precision in time...
View ArticleBy: Why i chose Raspberry instead of Arduino Yun and Spark-Core in the end |...
[…] it’s limit in reading analog sensors for instance. In my case i got around this by using i2c and a trick for the light-sensor (first time i used a capacitor, […]
View ArticleBy: rpa
Thanks for your tutorial! Is a 3.3 uF capacitor ok to use for the circuit? I don’t have a 1 uF capacitor available yet. I hope it does not cause something like short circuit…
View ArticleBy: Matt
That would be OK. It will just change the timing calculations as the time constant will be based on 3.3uF rather than 1uF.
View ArticleBy: Experiment: use an arduino as a slave to your raspberry pi | Project Pi
[…] in between). Now there are some cool ways around this if you are into your electronics (see here or here). But there are a couple of good reasons for using an Arduino as ‘slave’ to read […]
View ArticleBy: st
Great tutorial. I used this technique to monitor two different LDRs to notify me if I had accidentally left lights on in two outbuildings. Just counted number of loops; low number meant light was on,...
View ArticleBy: Pi2015
Great Article! I have been working off of the same Adafruit article for a Light Detection system of my own. I have one question id like to ask. How would one go about scaling this up? How do you go...
View ArticleBy: Matt
To be honest this technique probably isn't the way to go if you've got lots of sensors. You would have to poll each one and wait for the result and this would start to add a larger delay to your...
View ArticleBy: Aya
“With a 10Kohm resistor and a 1uF capacitor t is equal to 1 millisecond. In the dark the LDR may have a resistance of 10Mohm which would give a time of 1 second.” Don’t you mean : “With a (1Kohm)...
View ArticleBy: Matt
Well spotted. I’ve updated the numbers and added a link to a time constant calculator.
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