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Sensors, Actuators, and Robotics » Photo Cell

January 21, 2012
by Pr0ject
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Hello everyone, I am working on a project in order to find out where to put my tomato plant in my house and get the maximum amount of sunlight. In order to do this I have a Photo cell that I took from another kit. Now from the tests I have done it does seem to react to light levels. My question is can I equip it to nerdkits and if so what program code will I need to use?

I can provide an image of the Photo Cell if needed.

January 21, 2012
by treymd
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A while back I used a photocell with the ADC with some success, I simply modified the tempsensor code to do so, and used a voltage divider with the photocell as suggested by someone on here. There is most definitly a better way to connect the cell to the ADC, though I am no expert. The photocell I used was your typical resistive cds photocell from radio shack. The top surface has S-like squiggly lines on it.

January 21, 2012
by Ralphxyz
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PrOject lets see a picture of your Photo Cell.

From some quick googling it does not appear that a CDS photo cell would give you the type of accuracy you probable want.

It would be neat to have a Nerdkit light meter.

I am thinking of making a gate opener operate off car headlights flashing.

The gate would not be for security just to discourage people from randomly driving through.

So I was thinking of flashing headlights to activate the gate.

I am not sure what different ambient lighting levels might do and I would not want to open the gate just because someone pulled up at night with their headlights on. Possible I could detect three quick flashes.

I am not sure what type of photo detector to use.

I also thought of using horn beeps (well my Honda Civic Hybrid just beeps, it definitely does not HONK).

Ralph

January 22, 2012
by Pr0ject
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Alt Text

That's a picture of the PhotoCell I'm going to use, I am not looking fro precision but rather to see IF there is a difference in the light levels. After further research I have found the answers I was looking for, if you would like I could post a link of a very helpful sight that refers to the nerdkit's microcontroler.

Ralph your idea is very neat and will work I am sure. I have an idea that you could program so that when it gets a certain amount of light (for this you will need to test how much light the car makes) and then waits for a different light and repeat three times, then the gate will open. Of course this is just an idea to start off and there needs to be a line that resets the light counter.

January 23, 2012
by Ralphxyz
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Hey Pr0ject, post that link to that helpful site.

Ralph

January 23, 2012
by Pr0ject
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Here you go:

https://sites.google.com/site/qeewiki/books/avr-guide/analog-input

Hope you find something useful.

January 25, 2012
by BobaMosfet
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CDS are very sensitive. You need to understand hysterisis, and how far to offset them, so you get the range you want, but they are very sensitive.

BM

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