I would like some advice on Line Following robot please

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I'm about to modify my photovore to also give it line following ability, and have a couple of questions. I should mention I will be using LDR's.

1) What is the best colour LED to use to shine onto the floor, white, red or infra red?

2) Is it best to have the LED in front of the LDR, or to the side?

3) If to the side, should the LED be inside or outside the LDR?

4) Should the LDR be slightly lower than the LED or vice versa?

Thank you for your help.

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AmandaLDR

Fritsl made a tutorial about using LEDs and LDRs for that purposes.

https://www.robotshop.com/letsmakerobots/node/1833

 

I think it’s a good example.

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Many thanks for the link.

Many thanks for the link, XicoMBD. I have already read fritsl’s tutorial with interest, and intend shortly to replicate his AmandLDR object avoider using led’s and ldr’s. It doesn’t really help me with my specific questions though, but thanks for the link, anyway.

 

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1) LDRs have a reasonably

1) LDRs have a reasonably wide response to visible light, but the surface you’re shining the light on may not be so forgiving. If you use a white LED (or even an RGB LED) then you’ll get a more consistent amount of light returned to the LDR, regardless of the colour of the floor. If the floor is always going to be the same however, you could go for a specific colour instead.

2) ‘To the side’ is a common choice for bots, although industrial infrared sensors are usually oriented the other way. In your case you won’t notice any real different since the sensors will typically be close to the floor, so just go for whatever orientation makes for easier assembly.

3) Again it doesn’t really matter - getting the alignment of the LED & LDR correct is the main thing. For maximum sensitivity you’ll want the LED & LDR both aiming for the same spot on the floor, with the LDR’s center axis aligned to the reflection of the LED’s axis, for optimum exposure to reflected light. Don’t forget to shield your LDR against off-axis light to improve your readings =)

4) Having the LDR slightly lower from the LED can help reduce light from the LED hitting the LDR directly. After all, it’s only the reflected light you’re interested in. If your LDR has a good shield around it then it won’t really make any difference.

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Many thanks for your

Many thanks for your comprehensive reply, Telefox.

You have pretty much confirmed what I suspected, and the information will enable me to get on and start construction.

Thanks again, you’re a star :slight_smile: